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1
Kibar, Alp Aykut. "Investigation Of The Effect Of Dissimilar Channel Angular Pressing Method To The Mechanical And Microstuctural Properties Of 6061 Aluminum Alloy Sheets." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612140/index.pdf.
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Dissimilar Channel Angular Pressing (DCAP) method is an effective Severe Plastic Deformation (SPD) technique to improve the mechanical properties of sheets or strips by producing ultrafine grains. The aim of this study is to investigate the evolution of the microstructure and the improvement in mechanical properties of 6061 Al-alloy strips deformed by DCAP up to 5 passes. Mechanical properties such as hardness and strength have been observed to increase up to a certain strain level depending on the microstructural evolution. These microstructural changes were investigated by the characterization studies of XRD, SEM and TEM analysis of the DCAPed samples indicating the subgrain formation, changes in the dislocation density and dislocation behaviors.
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Borodachenkova, Marina. "Severe plastic deformation of Al–Zn alloys." Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/15492.
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Doutoramento em Engenharia Mecânica<br>In this work, the R&D work mainly focused on the mechanical and microstructural analysis of severe plastic deformation (SPD) of Al–Zn alloys and the development of microstructure–based models to explain the observed behaviors is presented. Evolution of the microstructure and mechanical properties of Al–30wt% Zn alloy after the SPD by the high–pressure torsion (HPT) has been investigated in detail regarding the increasing amount of deformation. SPD leads to the gradual grain refinement and decomposition of the Al–based supersaturated solid solution. The initial microstructure of the Al–30wt% Zn alloy contains Al and Zn phases with grains sizes respectively of 15 and 1 micron. The SPD in compression leads to a gradual decrease of the Al and Zn phase grain sizes down to 4 microns and 252 nm, respectively, until a plastic strain of 0.25 is reached. At the same time, the average size of the Zn particles in the bulk of the Al grains increases from 20 to 60 nm and that of the Zn precipitates near or at the grain boundaries increases as well. This microstructure transformation is accompanied at the macroscopic scale by a marked softening of the alloy. The SPD produced by HPT is conducted up to a shear strain of 314. The final Al and Zn grains refine down to the nanoscale with sizes of 370 nm and 170 nm, respectively. As a result of HPT, the Zn–rich (Al) supersaturated solid solution decomposes completely and reaches the equilibrium state corresponding to room temperature and its leads to the material softening. A new microstructure–based model is proposed to describe the softening process occurring during the compression of the supersaturated Al–30wt% Zn alloy. The model successfully describes the above–mentioned phenomena based on a new evolution law expressing the dislocation mean free path as a function of the plastic strain. The softening of the material behavior during HPT process is captured very well by the proposed model that takes into consideration the effects of solid solution hardening and its decomposition, Orowan looping and dislocation density evolution. In particular, it is demonstrated that the softening process that occurs during HPT can be attributed mainly to the decomposition of the supersaturated solid solution and, in a lesser extent, to the evolution of the dislocation mean free path with plastic strain.<br>Este trabalho foi dedicado à análise mecânica e microestrutural de uma liga Al–Zn submetida a um processo de deformação plástica severa (SPD) e ao desenvolvimento de modelos microestruturais para descrever os comportamentos observados. Foi investigada detalhadamente a evolução das propriedades mecânicas e da microestrutura da liga Al–30wt% Zn, após ensaios de torção a alta pressão (HPT), em função do grau de deformação. A SPD promoveu o refinamento gradual do grão e a decomposição da solução sólida de base Al sobressaturada. A microestrutura inicial da liga Al–30wt% Zn continha fases de Al e Zn com grãos de tamanhos 15 e 1 m, respetivamente. A deformação plástica até 0.25, em compressão, promoveu a diminuição gradual do tamanho dos grãos de Al e Zn até 4 m e 252 nm, respetivamente. Simultaneamente, o tamanho médio das partículas de Zn na rede cristalina de grãos de Al aumentou de 20 para 60 nm e, de forma idêntica, também aumentaram os precipitados de Zn na proximidade ou nos contornos de grão. Esta transformação microestrutural foi acompanhada, à escala macroscópica, por um forte amaciamento da liga. Os ensaios HPT foram conduzidos até uma deformação de corte de 314. Com esta SPD, as dimensões dos grãos de Al e Zn diminuiram até à nanoescala; para 370 nm e 170 nm, respetivamente. Como resultado do ensaio HPT, a solução sólida sobressaturada de Al rica em Zn decompôs–se completamente e atingiu o estado de equilíbrio à temperatura ambiente, com o consequente amaciamento do material. Foi criado um novo modelo, baseado na microestrutura do material, que permite descrever o processo de amaciamento que ocorre durante a forte compressão da liga Al–30wt% Zn. O fenómeno foi definido por uma nova lei que relaciona o caminho livre médio das deslocações com a deformação plástica. O modelo proposto permite prever muito bem o amaciamento do material durante o processo HPT, tendo em consideração os efeitos do endurecimento por solução sólida e sua decomposição, o mecanismo de Orowan e a evolução da densidade de deslocações. Em particular, ficou demonstrado que o processo de amaciamento que ocorre durante o ensaio HPT pode ser atribuído principalmente à decomposição da solução sólida sobressaturada e, em menor medida, à evolução do caminho livre médio das deslocações com a deformação plástica.
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MAGRO, TOMMASO. "Severe plastic deformation by backward tube flowforming." Doctoral thesis, Università degli studi di Padova, 2022. http://hdl.handle.net/11577/3459215.
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Tailored components are increasingly used in modern industry, as they allow the exploitation of key properties, such as strength, thickness, corrosion protection, type of material, in specific areas of interest of the workpiece, removing the weight where not necessary for performance purposes. It is possible to use a class of processes called “Severe Plastic Deformation” to modify some of these properties. Through the considerable refinement of the crystalline grain resulting from the high plastic deformation to which the component is subjected, not only does the resistance of the material increase, but also decreases the presence of internal defects, and consequently increases the fatigue resistance. The smaller dimensions of the crystalline grain are finally linked to a higher resistance to corrosion.
These processes, developed by the most common massive deformation processes such as extrusion, torsion, bending, rolling, are subject to various critical issues, including the laboratory-scale dimensions of the components that can be produced, resulting in poor industrial applicability, the problematic design and implementation of the process, and finally the high costs. From a review of the literature, it was possible to identify some critical points of scientific interest, first of all, the need to develop a process that at the same time guarantees a double objective: to obtain a component with high mechanical characteristics, typical of SPD processes, but with of suitable dimensions for possible use on an industrial scale. To implement a similar approach, attention was focused on the tube flowforming process, also known as tube spinning, which is generally not included among the SPD processes. However, since there are many elements in common (high refinement of the crystalline grain, absence of internal defects, high plastic strain), it was decided to use this technique to obtain two different types of products. The first is a tubular element, very difficult to make at present given the buckling and sticking problems, while the second type of product that can be obtained is a flat element, characterized by the same properties of the tubular component, obtained after cutting and straightening conducted on the tube.
The purpose of this PhD thesis is to evaluate the feasibility of using the backward tube flowforming process to obtain tailored SPD components, thus assessing the influence of various process parameters both numerically and experimentally in some of the properties of the final component. To this end, two different equipment have been developed to perform the experimental tests, a traditional one, designed starting from the peculiar characteristics of the process available in the literature and simulated numerically, and an innovative equipment that uses a constraint placed radially to the tube, helpful in increasing the strain imposed during the process and improving the surface quality of the final component.
The experimental tests, carried out using the AA6082-T4 alloy as reference material, allowed us to evaluate the variations in the mechanical characteristics of the starting material, reporting a high increase in microhardness and mechanical properties intended as yield strength and UTS. At the same time, following the theoretical result that associates an increase in mechanical performance with a decrease in the size of the crystalline grain, there was a high reduction in the size of the crystalline grain, with a portion of the tube characterized by a structure with microstructure highly refined, typical of SPD processes. The high deformation impressed on the tubular elements led to a reduction in ductility, which in any case did not affect the execution of the flattening process performed downstream of the flowforming process, allowing to obtain plates characterized by the same microstructure and mechanical characteristics of the initial flowformed tube.<br>L’utilizzo di componenti “su misura” trova sempre più spazio nell'industria moderna, poiché il loro impiego permette di sfruttare delle proprietà chiave, quali resistenza, spessore, protezione dalla corrosione, tipologia del materiale, in specifiche aree di interesse del pezzo, rimuovendo il peso dove non necessario ai fini prestazionali. Per modificare alcune di queste proprietà è possibile utilizzare una tipologia di processi denominata “Severe Plastic Deformation”. Tramite il notevole raffinamento della grana cristallina conseguente all’elevata deformazione plastica a cui il componente è soggetto, si ottiene un aumento della resistenza del materiale, ma si diminuisce la presenza di difetti interni, e conseguentemente si aumenta la resistenza a fatica. Le dimensioni inferiori della grana cristallina sono infine collegate ad una più elevata resistenza alla corrosione.
Questi processi, sviluppati partendo dai più comuni processi di deformazione massiva quali estrusione, torsione, piegatura, laminazione, sono soggetti a diverse criticità, tra cui: le dimensioni su scala di laboratorio dei componenti che possono essere prodotti, con conseguente scarsa applicabilità industriale, la difficile progettazione e realizzazione del processo, e infine i costi elevati. Da una revisione della letteratura è stato possibile individuare alcuni punti critici di interesse scientifico, primo tra tutti l’esigenza di sviluppare un processo che allo stesso tempo garantisce un obiettivo duplice: ottenere un componente con caratteristiche meccaniche elevate, tipico dei processi SPD, ma con delle dimensioni idonee ad un eventuale utilizzo su scala industriale. Per attuare un simile approccio l’attenzione è stata focalizzata sul processo di tube flowforming, che generalmente non si annovera tra i processi SPD. Essendo molteplici gli elementi in comune (elevato raffinamento della grana cristallina, assenza di difetti interni, elevata deformazione plastica) si è deciso di utilizzare questa tecnica per ottenere due diverse tipologie di prodotto. Il primo è un elemento tubolare, molto difficile da realizzare allo stato attuale visti i problemi di buckling e sticking, mentre il secondo è un elemento piatto, caratterizzato dalle stesse proprietà dell’elemento tubolare, ricavato dopo le operazioni di taglio e spianatura condotte sul tubo.
Lo scopo di questa tesi di dottorato è quello di valutare la fattibilità nell’utilizzo del processo di backward tube flowforming per ottenere componenti con microstruttura raffinata creati “su misura”, valutando quindi sia a livello numerico sia a livello sperimentale l’influenza di vari parametri di processo su alcune delle proprietà del componente finale. A tal fine per eseguire le prove sperimentali sono state sviluppate due diverse attrezzature, una tradizionale, progettata partendo dalle caratteristiche peculiari del processo reperibili in letteratura e simulate numericamente, ed un’attrezzatura innovativa che utilizza un vincolo radiale, utile per aumentare la deformazione impressa durante il processo e per aumentare la qualità superficiale del componente finale.
Le prove sperimentali, condotte utilizzando come materiale di riferimento la lega di alluminio 6082-T4, hanno permesso di valutare le variazioni delle caratteristiche meccaniche del materiale di partenza, riportando un elevato incremento di durezza e delle proprietà meccaniche intese come limite di snervamento e UTS. Allo stesso tempo si è avuta un’elevata riduzione della dimensione del grano cristallino, con una porzione di tubo caratterizzata da una microstruttura altamente raffinata. L’elevata deformazione ha comportato una riduzione della duttilità, che comunque non ha influito sull'esecuzione del processo di spianatura e di ottenere piatti con caratteristiche uguali al tubo flowformato di partenza.
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Yapici, Guney Guven. "Severe plastic deformation of difficult-to-work alloys." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/531.
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The present work aims to reveal the microstructural evolution and post-processing mechanical behavior of difficult-to-work alloys upon severe plastic deformation. Severe plastic deformation is applied using equal channel angular extrusion (ECAE) where billets are pressed through a 90o corner die achieving simple shear deformation. Three different materials are studied in this research, namely Ti-6Al-4V, Ti-6Al-4V reinforced with 10% TiC and AISI 316L stainless steel. Microstructure and mechanical properties of successfully extruded billets were reported using light microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), tension and compression experiments and microhardness measurements. The effects of extrusion conditions (temperature and processing route) on the microstructure and mechanical properties are investigated. The underlying mechanisms responsible for observed mechanical behaviors are explored. It is seen that ECAE shear deformation leads to refinement in α plates and elimination of prior β boundaries in Ti-6Al-4V. Decreasing extrusion temperature and increasing number of passes decreases α plate size and grain size. Refined α grain size leads to a significant increase in tensile and compressive flow stresses at room temperature. Texture produced by ECAE has a pronounced effect on mechanical properties. Specifically it leads to tension/compression asymmetry in flow strengths and strain hardening coefficients may be described by the activation of differing slip systems under tension and compression loading. ECAE of Ti-6Al-4V+10%TiC samples also improved mechanical properties due to α plate size refinement. Nevertheless, further extrusion passes should be carried out for tailoring reinforcement size and distribution providing optimum strength and ductility. ECAE deformation of AISI 316L stainless steel at high homologous temperatures (0.55 to 0.60 Tm) results in deformation twinning as an effective deformation mechanism which is attributed to the effect of the high stress levels on the partial dislocation separation. Deformation twinning gives rise to high stress levels during post-processing room temperature tension and compression experiments by providing additional barriers to dislocation motion and decreasing the mean free path of dislocations. The highest tensile flow stress observed in the sample processed at 700 oC following one pass route A was on the order of 1200 MPa which is very high for 316L stainless steel. The ultimate goal of this study is to produce stabilized end microstructures with improved mechanical properties and demonstrate the applicability of ECAE on difficult-to-work alloys.
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Tan, Evren. "Severe Plastic Deformation Of Age Hardenable Aluminum Alloys." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614968/index.pdf.
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Industrial products of high-strength Al-alloys are currently manufactured by thermo-mechanical processes, which are only applicable in the integrated plants requiring high investment cost. Moreover, reduction of the average grain size not less than 10 &mu<br>m and re-adjustment of process parameters for each alloy type is evaluated as disadvantage. Therefore, recently there have been many research studies for development of alternative manufacturing techniques for aluminum alloys. Research activities have shown that it is possible to improve the strength of Al-alloys remarkably by severe plastic deformation which results in ultra-fine grain size.
This study aims to design and manufacture the laboratory scale set-ups for severe plastic deformation of aluminum alloys, and to characterize the severely deformed samples. The stages of the study are summarized below:
First, for optimization of die design and investigation of parameters affecting the deformation finite element modeling simulations were performed. The effects of process parameters (die geometry, friction coefficient) and material properties (strain hardening, strain-rate sensitivity) were investigated.
Next, Equal Channel Angular Pressing (ECAP) system that can severely deform the rod shaped samples were designed and manufactured. The variations in the microstructure and mechanical properties of 2024 Al-alloy rods deformed by ECAP were investigated.
Finally, based on the experience gained, a Dissimilar Channel Angular Pressing (DCAP) system for severe plastic deformation of flat products was designed and manufactured<br>then, 6061 Al-alloy strips were deformed. By performing hardness and tension tests on the strips that were deformed by various passes, the capability of the DCAP set-up for production of ultra-fine grain sized high-strength aluminum flat samples were investigated.
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Mathaudhu, Suveen Nigel. "Fabrication of amorphous metal matrix composites by severe plastic deformation." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4389.
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Bulk metallic glasses (BMGs) have displayed impressive mechanical properties, but
the use and dimensions of material have been limited due to critical cooling rate
requirements and low ductility. The application of severe plastic deformation by equal
channel angular extrusion (ECAE) for consolidation of bulk amorphous metals (BAM)
and amorphous metal matrix composites (AMMC) is investigated in this dissertation.
The objectives of this research are a) to better understand processing parameters which
promote bonding between particles and b) to determine by what mechanisms the
plasticity is enhanced in bulk amorphous metal matrix composites consolidated by
ECAE.
To accomplish the objectives BAM and AMMCs were produced via ECAE
consolidation of Vitreloy 106a (Zr58.5Nb2.8Cu15.6Ni12.8Al10.3-wt%), ARLloy #1
(Hf71.3Cu16.2Ni7.6Ti2.2Al2.6 -wt%), and both of these amorphous alloys blended with
crystalline phases of W, Cu and Ni. Novel instrumented extrusions and a host of postprocessing
material characterizations were used to evaluate processing conditions and
material properties. The results show that ECAE consolidation at temperatures within the supercooled liquid region gives near fully dense (>99%) and well bonded millimeter
scale BAM and AMMCs. The mechanical properties of the ECAE processed BMG are
comparable to cast material: ÃÂf = 1640 MPa, õf = 2.3%, E = 80 GPa for consolidated
Vitreloy 106a as compared to ÃÂf = 1800 MPa, õf = 2.5%, E = 85 GPa for cast Vitreloy
106, and ÃÂf = 1660 MPa, õf = 2.0%, E = 97 GPa for ARLloy #1 as compared to ÃÂf = 2150
MPa, õf < 2.5%, E = 102 GPa for Hf52Cu17.9Ni14.6Ti5Al10. The mechanical properties of
AMMCs are substandard compared to those obtained from melt-infiltrated composites
due to non-ideal particle bonding conditions such as surface oxides and crystalline phase
morphology and chemistry. It is demonstrated that the addition of a dispersed crystalline
phase to an amorphous matrix by ECAE powder consolidation increases the plasticity of
the amorphous matrix by providing locations for generation and/or arrest of adiabatic
shear bands. The ability of ECAE to consolidated BAM and AMMCs with improved
plasticity opens the possibility of overcoming the size and plasticity limitations of the
monolithic bulk metallic glasses.
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Zhang, Nianxian. "Processing of a two-phase alloy by severe plastic deformation." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/388051/.
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This thesis presents a systematic study on evolutions of microstructure, microhardness and superplasticity of a Pb-62% Sn alloy processed by both equal-channel angler pressing (ECAP) and high-pressure torsion (HPT) and the subsequent self-annealing process at room temperature (RT). The Pb-Sn alloy exhibits characteristics with significant grain refinement after processing by ECAP and HPT but with a reduction in the hardness values by comparison with the initial as-cast condition. For HPT processing, it is shown that there are generally smaller grains at the edges of the discs by comparison with the disc centres. The hardness results are different from those generally reported for conventional single-phase materials where a hardening trend was commonly observed after HPT processing. The significance of this difference is examined. The microstructures of the alloy after HPT were repeatedly investigated during the course of self-annealing by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and scanning electron microscopy (TEM). A significant grain growth combined with increase of microhardness was observed. It was demonstrated that there was a large fraction of twin boundaries with a twin relationship of 62.8°<100> in the microstructure for the as-cast condition. Owing to the presence of high pressure, the mobility of Ʃ21 boundaries at 71° was greatly favoured during processing by HPT. But the mobility of the dislocation-twin boundary near 62.8°<100> was favoured during self-annealing at RT once the high pressure was removed. The HPT processing significantly increased the solubility of Sn in Pb phase. This supersaturated state of Sn in Pb is, however, not stable at RT during self-annealing and therefore a decomposition of Sn from Pb-rich phase was observed after 16 days of storage. Lattice diffusion should be considerable as the main mechanism for the decomposition. Moreover, abnormal grain growth was observed to be greatly favoured during self-annealing when the introduced strain was relatively low, i.e. 2 passes by ECAP and the centre region of a HPT-processed disc after one turn. Consequently, a series of HPT-processed samples with different storage time was tested in tension at RT and at 1.0 × 10-4 - 1.0 × 10-1 s-1. The results demonstrated that, despite the storage time, all processed alloy exhibited excellent RT superplasticity at 1.0 × 10-4 s-1 and the highest elongation of 630% was recorded in the processed alloy after storage for 4 days at RT. The detailed investigation showed, due to the high strain rate sensitivity of the processed alloy, a transition strain rate of ~1.0 × 10-2 s-1 was observed in which stain softening with ductile behaviour is apparent due to active GBS below the transition point but high strength is observed because of grain boundary strengthening above the transition during plastic deformation at RT in the Pb-Sn alloy after HPT. Nanoindentation tests were then performed applying both indentation depth-time (h-t) relationship at holding stage and the hardness, H, at various loading rates to explore the evolution of strain rate sensitivity (SRS), m. The results obtained by both tensile test and nanoindentation show that the relatively fast self-annealing of the HPT-processed Pb-62% Sn eutectic alloy is occupying by an unambiguous changing-tendency of strain rate sensitivity. The results confirm the validity of using nanoindentation for measuring strain rate sensitivity.
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Alhajeri, Saleh N. "Processing of aluminium and titanium alloys by severe plastic deformation." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/185107/.
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Shen, Ninggang. "Microstructure prediction of severe plastic deformation manufacturing processes for metals." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6282.
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The objective of the research presented in this thesis has been to develop a physics-based dislocation density-based numerical framework to simulate microstructure evolution in severe plastic deformation (SPD) manufacturing processes for different materials. Different mechanisms of microstructure evolution in SPD manufacturing processes were investigated and summarized for different materials under dynamic or high strain rates over a wide temperature range. Thorough literature reviews were performed to clarify discrepancies of the mechanism responsible for the formation of nanocrystalline structure in the machined surface layer under both low-temperature and high-temperature conditions.
Under this framework, metallo-thermo-mechanically (MTM) coupled finite element (FE) models were developed to predict the microstructure evolution during different SPD manufacturing processes. Different material flow stress responses were modeled subject to responsible plastic deformation mechanisms. These MTM coupled FE models successfully captured the microstructure evolution process for various materials subjected to multiple mechanisms.
Cellular automaton models were developed for SPD manufacturing processes under intermediate to high strain rates for the first time to simulate the microstructure evolution subjected to discontinuous dynamic recrystallization and thermally driven grain growth. The cellular automaton simulations revealed that the recrystallization process usually cannot be completed by the end of the plastic deformation under intermediate to high strain rates. The completion of the recrystallization process during the cooling stage after the plastic deformation process was modeled for the first time for SPD manufacturing processes at elevated temperatures.
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Gzyl, Michael. "Improving mechanical properties of a magnesium alloy by severe plastic deformation." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24213.
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Magnesium alloys are very promising materials for automotive and aerospace applications due to their low density. The market of medical implants (e.g. temporary orthopaedic and cardiovascular implants) is another field of possible applications of magnesium alloys since they can completely dissolve within human body without causing any major health issues. Unfortunately, magnesium alloys have been well-known from their low formability at room temperature and poor corrosion resistance. The aim of the current work was to improve mechanical properties of a magnesium alloy by incremental equal channel angular pressing (I-ECAP). The goal of the process is to refine grain structure of a continuous bulk metallic billet without changing its dimensions. In the current work, the most popular wrought magnesium alloy AZ31B was subjected to I-ECAP for the first time to confirm potential of the method for industrial production of innovative lightweight materials. The process window was determined on the basis of I-ECAP experiments conducted with various process parameters (temperature, processing route, initial grain size of the alloy). Additionally, various microstructural characterization methods, including ex situ and in situ analyses, were incorporated in this work to show a relation between the grain size and the deformation mechanisms occurring in the alloy. It was found that mechanical properties of AZ31B can be tailored to a specific application by using different process parameters. It was shown that yield strength can be increased from 165 MPa to 290 MPa when temperature of I-ECAP is reduced to 150°C. Moreover, room temperature ductility of the produced material can exceed 40% when a combination of I-ECAP and subsequent heat treatment is applied. The results of the work confirmed that I-ECAP could be considered as the useful method for producing advanced lightweight metallic materials with a potential for industrial applications.
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Wang, Chuan Ting. "Tribological behaviour of ultrafine-grained alloys formed by severe plastic deformation." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/355702/.
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This thesis presents a study on wear behaviour of materials processed by severe plastic deformation (SPD). Al-1050 alloy and commercial purity Ti have been processed via different SPD methods. Wear tests of different contact size were employed to compare the wear performance between ultrafine grained (UFG) alloys and their as-received state. The aim of this study is to understand the effect of SPD processing on wear behaviour of materials, to seek a way to use SPD processing to improve the mechanical properties of materials and their wear resistance at the same time. Al-1050 was processed using equal-channel angular pressing(ECAP) and highpressure torsion (HPT), respectively. Microhardness evolution was analysed by Vickers hardness testing. The results showed clear evidence of strength improvement by SPD. Afterwards, dry sliding testing was performed on a TE77 tribometer against different counter materials. The results showed that both ECAP and HPT led to a decrease to the wear resistance to Al-1050. Scanning electron microscopy, energy dispersion spectroscopy and surface profile meter were used to examine the worn surface and debris. The transition from severe platelet wear to oxidation wear was observed during the wear tests. The decrease of wear resistance of Al-1050 after SPD processing is attributed to a lack of work hardening capacity during the severe wear stage and a higher oxidation rate during the oxidation wear stage. In addition, commercial purity Ti was processed via HPT and heat treatment. Mechanical testing and a microstructure study demonstrated the trend of increasing strength with decreasing grain size. In this study, the micro-tribological behaviour of UFG Ti was studied for the first time via microscratch testing. The results showed that HPT-processing of Ti inhibited operation of adhesion and ploughing during wear tests and led to better wear resistance. Based on the results from the above studies and a comprehensive review of published research on wear of UFG alloys, a conclusion was drawn that when the wear process is dominated by adhesion andoxidation wear, SPD processing decreases the wear resistance of materials. However, when wear is dominated by mechanical wear mechanisms (plastic deformation, abrasion and ploughing), the strengthening of SPD processing brings better wear performance to the material. To enhance the wear resistance of UFG Ti as bio-implant materials, TiN and DLC coatings were deposited on to Ti substrates via physical vapour deposition methods. Wear tests indicated a significant improvement of wear resistance after coating deposition. Adhesion tests showed that the thin coatings had much enhanced load bearing capacity with UFG Ti as the substrate compared to coarse-grained Ti, which is explained by a modified composite hardness model. This model showed good accuracy in predicting the critical load of a wide range of thin coatings on different substrates. Finally, an improved bio-implant design was proposed for total joint replacement applications. This design involves fabricating the main body of the bio-implant from UFG pure Ti processed by SPD and subsequently applying a hard thin coating to protect the head of the implant. It is anticipated this design will provide the implant with high strength, good fatigue life, good corrosion resistance, together with good wear and tribo-corrosion resistance from the coating and a non-toxic ion release. The product is aimed to replace the toxic bio-metals in total joint replacement use, such as SS316, Co-Cr alloy and Ti-6Al-4V. Therefore, the design has a very strong application prospect.
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Alobaid, Baleegh. "SYNTHESIS AND CHARACTERIZATION OF MAGNESIUM - TITANIUM COMPOSITES BY SEVERE PLASTIC DEFORMATION." UKnowledge, 2018. https://uknowledge.uky.edu/cme_etds/91.
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Magnesium alloys are widely used in engineering applications, including aerospace and automobile industries, due to their desirable properties, such as lower density, high damping capacity, relatively high thermal conductivity, good machinability, and recyclability. Researchers have, therefore, been developing new magnesium materials. However, mechanical and corrosion properties are still limiting many commercial applications of magnesium alloys. In this Ph.D. thesis research, I developed Mg-Ti composite materials to offer some solutions to further improve the mechanical behavior of magnesium, such as titanium-magnesium (Ti-Mg) claddings, Mg-Ti multilayers, and Ti particle enforced Mg alloys. Low cost manufacturing processes, such as hot roll-bonding (RB) and accumulative roll-bonding (ARB) techniques, were used to produce Mg-Ti composites and sheets. The microstructural evolution and mechanical properties of composites were investigated using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), nanoindentation, and tensile tests.
In the first part of this study, I investigated the bonding strength of the AZ31/Ti to understand the mechanical properties of Mg/Ti composites. Using a single pass RB process, I fabricated AZ31/Ti multilayers with the thickness reduction in a range of 25% to 55%. The hot-rolled AZ31/Ti multilayers were heat-treated at 400 °C for 6, 12, and 24 hours, respectively, in an argon atmosphere. Tensile-shear tests were designed to measure the bonding strength between AZ31/Ti multilayers. Furthermore, the experimental results revealed good bonding of the AZ31/Ti multilayers without forming any intermetallic compounds in the as-rolled and heat-treated AZ31/Ti multilayers. The good bonding between Ti and AZ31 is the result of diffusion bonding whose thickness increases with increasing heat-treatment time and thickness reduction. The shear strength of the Ti/AZ31 multilayer increases with increasing bonding layer thickness.
In the second part of this study, I characterized the microstructure and texture of three-layered Ti/AZ31/Ti clad sheets which were produced by single-pass hot rolling with a reduction of thickness 38% (sheet I) and 50% (sheet II). The AZ31 layer in sheets I and II exhibited shear bands and tensile twins {1012}⟨1001⟩ . The shear bands acted as local strain concentration areas which led to failure of the clad sheets with limited elongation. Heat treatment caused changes in the microstructure and mechanical properties of clad sheets due to static recrystallization (SRX) on twins and shear bands in the AZ31 layer. Recrystallized grains usually randomize the texture which causes weaken the strong deformed (0001) basal texture. Twins served as nucleation sites for grain growth during SRX. Tensile tests at room temperature showed significantly improved ductility of the clad sheets after heat treatment at 400°C for 12h. The results showed that the mechanical properties of clad sheets II are better than clad sheet I: The clad sheet II shows elongation 13% and 35% along the rolling direction (RD) for as-rolled and annealed clad sheet, respectively whereas the clad sheet I shows elongation 10% and 22% along RD for as-rolled and annealed clad sheet, respectively.
In the final part of this study, I examined the effects of dispersed pure titanium particles (150 mesh) with 0, 2.3, 3.5, 4.9, and 8.6 wt. % on the microstructure and mechanical properties of AZ31-Mg alloy matrix. Mg-Ti composites were processed through three accumulative roll bonding (ARB) steps using thickness reductions of 50% in each pass followed by heat treatment at 400 °C for 12 h in an argon atmosphere. ARB is an efficient process to fabricate Mg-Ti composites. Mechanical properties of Mg- 0Ti and Mg-2.3Ti composite were enhanced by ~ 8% and 13 % in yield strength and ~ 30% and 32 % in ultimate tensile strength, respectively. Meanwhile, the elongation of the composites were decreased by 63% and 70%, respectively. After heat treatment, the results showed a decrease in yield strength and increase in elongation to fracture. The mechanical properties of the Mg-0 and Mg-2.3Ti composite were enhanced: ultimate tensile strength by 9% and 7%, and elongation by 40% and 67%, while the yield strength was decreased by 28% and 36% compared with the initial AZ31. Enhancements of strength and ductility were the results of two mechanisms: a random matrix texture by ARB and ductile titanium particle dispersion.
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Mishra, Anuj. "Microstructural evolution in ultra-fine grained copper processed by severe plastic deformation /." Diss., Connect to a 24 p. preview or request complete full text in PDF formate. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3266841.
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Хоменко, Олексій Віталійович, Алексей Витальевич Хоменко, Oleksii Vitaliiovych Khomenko, et al. "Modeling of phase dynamics and kinetics of fragmentation at severe plastic deformation." Thesis, Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна Національної академії наук України, 2015. http://essuir.sumdu.edu.ua/handle/123456789/41631.
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Kachur, Stephen J. "Selective Internal Oxidation and Severe Plastic Deformation of Multiphase Fe-Y Alloys." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/1013.
Full textAbstract:
Oxide dispersion strengthened (ODS) alloys are known for their desirable mechanical properties and unique microstructures. These alloys are characterized by an even dispersion of oxide phase throughout a metallic matrix, and exhibit high strength and enhanced creep properties at elevated temperatures. This makes them ideal candidate materials for use in many structural applications, such as coal-fired power plants or in next generation nuclear reactors. Currently most often produced by mechanical alloying, a powder metallurgy based process that utilizes high energy ball milling, these alloys are difficult and costly to produce. One proposed method for forming ODS alloys without high-energy ball milling is to internally oxidize a bulk alloy before subjecting it to severe plastic deformation to induce an even oxide distribution. This work examines such a processing scheme with a focus on the internal oxidation behavior. Internal oxidation has been shown to occur orders of magnitude faster than expected in multi-phase alloys where a highly reactive oxidizable solute has negligible solubility and diffusivity in other, more-noble, phases. Commonly referred to as in situ oxidation, this accelerated oxidation process has potential for use in a processing scheme for ODS alloys. While in situ oxidation has been observed in many different alloy systems, a comprehensive study of alloy composition and microstructure has not been performed to describe the unusual oxidation rates. This work used Fe-Y binary alloys as model system to study effects of composition and microstructure. These alloys have been shown to exhibit in situ oxidation, and additionally, Y is typically introduced during mechanical alloying to form Y-rich oxides in Fe-based ODS alloys. Alloys with Y content between 1.5 and 15 wt% were prepared using a laboratory scale arc-melting furnace. These alloys were two phase mixtures of Fe and Fe17Y2. First, samples were oxidized between 600 and 800 °C for 2 to 72 hours, using a Rhines pack to maintain low oxygen partial pressures so that in situ oxidation could occur. Oxidation rates were accelerated when compared to traditional theory, and were not well described by a single parabolic rate constant throughout the duration of the experiment. While results agreed with Wagner theory that increased Y content should lead to decreased oxidation rates, this was attributed to a depletion of oxygen supply from the Rhines pack over time. Samples were also subjected to plastic deformation to observe how changes in microstructure influenced kinetics. Connectivity of the oxidizable phase was found to be critical to promoting the fastest rates of oxidation. Oxidation studies where then carried out using thermogravimetric analysis. A gaseous mixture of Ar-H2 was passed through a dew point control unit to vary oxidant partial pressure between 10-25 and 10-20 atm. Flow rate of the gas parallel to the sample surface was also altered. Canonical correlation analysis was then used to analyze and simplify the relationships between input and output variables. This analysis pointed to the importance of quantifying the relationship between the size of formed oxides and changes in oxidation kinetics over time. Where sustained parabolic kinetics were observed, oxides were small throughout the depth of internal oxidation. The effects of oxide size on penetration depth were then numerically modeled and incorporated into existing oxidation theory to show that the observed kinetics could be qualitatively described. After oxidation experiments, severe plastic deformation was applied to both oxidized and unoxidized microstructures using equal channel angular pressing. By manipulating pressing temperature and the number of passes, microstructures were altered to varying degrees of success. No oxide refinement was observed, but increasing temperatures and number of passes allowed for even dispersion of both oxides and Fe17Y2 intermetallic.
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Yurkova, A. I., A. V. Byakova, and M. Gricenko. "Ultrafine grain refinement of iron induced by severe plastic deformation in assistance of multi-directional deformation mode." Thesis, Sumy State University, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20573.
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Kulkarni, Ajay V. "Effect of ausforming via severe plastic deformation on shape memory behavior of NiTi." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/3246.
Full textAbstract:
In this study, Thermomechanical properties of Ti-50.8 and 50.7 at% Ni alloy severely deformed using Equal Channel Angular Extrusion (ECAE) are investigated. The aim of this study is to reveal the effects of severe plastic deformation on shape memory, pseudelasticity, interplay between plastic deformation via dislocation slip and twinning, and forward and reverse martensitic transformation. The samples are processed at room temperature, i.e. slightly above the austenite finish temperature, and at 450 °C, i.e. well-above the austenite finish temperature. Transformation temperatures, microstructural evolution, and thermomechanical properties of ECAE processed samples are studied before and after low temperature annealing heat treatment and compared with conventional cold drawn and precipitation hardened material. The unique findings are: 1) the observation of a mixture of heavily deformed B2 (austenite) and B19 (martensite) phases in the samples processed at room temperature although martensite stabilization was expected, 2) the observation of highly organized, twin-related nanograins in B2 phase of the samples deformed at room temperature which was attributed to B2 to B19' via SIM, and B19' to B2 via SPD (SIM: Stress Induced Martensitic transformation, SPD: Severe Plastic Deformation) transformation sequence, 3) simultaneous observation of B2 austenite and strain induced B19 martensite in the samples deformed at 450 °C, and 4) perfect pseudoelasticity, small pseudoelastic stress hysteresis and excellent cyclic response with no irrecoverable strain up to 1000 cycles for ECAE at 450 °C processed sample. Strain induced martensite in NiTi alloys was reported for the first time. The formation of well-organized twin-related nanograins via severe plastic deformation opens a new opportunity for twinning induced grain boundary engineering in NiTi alloys which significantly improves the matrix strength and the cyclic response against degradation of shape memory and pseudoelasticity.
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Трощенко, Дар`я Сергіївна, Дарья Сергеевна Трощенко, and Dar`ia Serhiivna Troshchenko. "Modeling the non-equlibrium evolutionary thermodynamics of fragmentation regime at severe plastic deformation." Thesis, Sumy State University, 2016. http://essuir.sumdu.edu.ua/handle/123456789/46928.
Full textAbstract:
Nowadays, metals are subjected to different forms of processing for
obtaining the high mechanical properties (high strength and plasticity). This
objective is achieved most cardinally at grinding the grain structure of
metals due to their processing by the methods of severe plastic deformation
(SPD).
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Haouaoui, Mohammed. "An investigation of bulk nanocrystalline copper fabricated via severe plastic deformation and nanoparticle consolidation." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4861.
Full textAbstract:
Ultrafine grained (UFG) and nanocrystalline materials have attracted considerable
interest because of their unique mechanical properties as compared with coarse grained
conventional materials. The fabrication of relatively large amounts of these materials still
remains a challenge, and a thorough understanding of the relationship between
microstructure and mechanical properties is lacking. The objective of this study was to
investigate the mechanical properties of UFG and nanocrystalline copper obtained
respectively by a top down approach of severe plastic deformation of wrought copper and
a bottom up approach of consolidation of copper nanoparticles using equal channel
angular extrusion (ECAE). A critical assessment and correlation of the mechanical
behavior of ECAE processed materials to the microstructure was established through the
determination of the effect of strain level and strain path on the evolution of strength,
ductility and yield anisotropy in UFG oxygen free high conductivity copper in correlation
with grain size, grain morphology and texture.
ECAE was shown to be a viable method to fabricate relatively large
nanocrystalline consolidates with excellent mechanical properties. Tensile strengths as
high as 790 MPa and fracture strain of 7 % were achieved for consolidated 130nm copper powder. The effects of extrusion route, number of passes and extrusion rate on
consolidation performance were evaluated. The relatively large strain observed was
attributed to the bimodal grain size distribution and accommodation by large grains. The
formation of bimodal grain size distribution also explains the simultaneous increase in
strength and ductility of ECAE processed wrought Cu with number of passes. Texture
alone cannot explain the mechanical anisotropy in UFG wrought copper but we showed
that grain morphology has a strong impact and competes with texture and grain
refinement in controlling the resulting yield strength. Tension-compression asymmetry
was observed in UFG wrought copper. This asymmetry is not always in favor of
compression as reported in literature, and is also influenced by grain morphology through
the interaction of dislocations with grain boundaries. Different prestrains in tension and
compression should be experimented to have a better understanding of the encountered
anisotropy in Bauschinger parameter in relation with the observed tension-compression
asymmetry.
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Mohseni, Hamidreza Materials Science & Engineering Faculty of Science UNSW. "Microstructural development and thermal stability of aluminium-based composites processed by severe plastic deformation." Awarded by:University of New South Wales. School of Materials Science and Engineering, 2006. http://handle.unsw.edu.au/1959.4/26793.
Full textAbstract:
Equal channel angular pressing ECAP is a process whereby simple shear is applied to a billet during multiple passages through an angled channel of constant cross section. The process is capable of generating very large plastic strains that significantly refines the microstructure without altering the external dimensions of the billet. A number of properties are influenced by grain refinement with the generation of a submicron grain structure SMG by ECAP resulting in improved strength and hardness and enhanced superplasticity. In this thesis, both an AA7075 alloy and AA7075 Al-base metal matrix composite MMC reinforced with 5 wt. percent of 50 nm diameter SiC particles was produced by a powder metallurgy route followed by hot extrusion. The materials were subsequently deformed by ECAP at 350 C to a true effective strain of 4.6 in an attempt to refine the microstructure and further distribute the SiC reinforcement phase in the composite. The high temperature microstructural stability of both the as-deformed alloy and composite was investigated to elucidate the effect of the reinforcement phase on continuous and discontinuous grain coarsening. It was found that ECAP generated a fine equiaxed grain size of ~ 2.3 !m and ~1.8 !m in the alloy and composite, respectively. The composite was more refined after ECAP since the SiC particles allow the matrix to undergo more grain refinement during deformation. ECAP was found to be a reasonable method for further distributing SiC clusters in this composite which is important for optimizing the reinforcement phase in terms of ambient temperature strengthening and enhanced grain stability at elevated temperature. Both the alloy and composite were annealed at times up to 5h at 500 C to assess grain stability. During annealing, the grain structure of both materials evolved in a continuous manner unlike the discontinuous process of recrystallization. Such a process is similar to continuous recrystallization observed in a range of heavily deformed Al alloys. Substantial grain boundary interactions with MgZn2 precipitates and oxide particles were found in the alloy, with precipitate, oxide and SiC particles found in the composite. The strong pinning force exerted by these particles minimised grain growth in both materials with the composite exhibiting a finer less than 2.5 !m grain size than the alloy less than 3.5 !m after extended annealing. This enhanced grain stability was attributed to the high volume fraction SiC particles which resulted in a large value of the dispersion parameter f/d which results in significant boundary pinning during annealing. Grain stability was also analysed in terms of a recently-proposed mean field model of annealing where it was predicted that the composite should not undergo discontinuous coarsening, as observed experimentally.
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Uribe, Restrepo Catalina. "Process-dependent microstructure and severe plastic deformation in SiCp?? reinforced aluminum metal matrix composites." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4712.
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Discontinuously reinforced MMCs with optimized microstructure are sought after for exceptional high strain rate behavior. The microstructure evolution of a stir-cast A359 aluminum composite reinforced with 30 vol.% SiCsubscript p] after isothermal anneal, successive hot-rolling, and high strain rate deformation has been investigated. Quantitative microstructural analysis was carried out for the as-cast, annealed (470??C, 538??C and 570??C) and successively hot rolled specimens (64, 75, 88, and 96% rolling reductions). Selected composites were also examined after high strain rate deformation. X-ray diffraction, optical microscopy, scanning electron microscopy and transmission electron microscopy were employed for microstructural characterization. The strength and ductility of the A359 Al alloys, and the composite, were greatly influenced by the brittle eutectic silicon phase and its morphology. Lamellar eutectic silicon spheroidized with isothermal anneal and successive hot rolling with a corresponding decrease in hardness. The hot rolling process also considerably decreased the SiC particle size (approximately 20% after 96% reduction) by breaking-up the hard SiC particles. However, this break-up of particles increased the homogeneity of SiCsubscript p] size distribution. Successive hot rolling also healed voids due to solidification shrinkage, incomplete infiltration of molten Al and defects originating from fractured particles. Four selected specimens of composites were examined after high strain rate deformation. Fractography and metallographic analysis for the craters, voids, and relevant regions affected by the high velocity impact were carried out. The deposition of impact residuals was frequently observed on the exposed fracture surfaces. These residuals were typically observed as "molten-and-solidified" as a consequence of excessive heat generated during and after the damage.; Particularly in regions of entry and exit of impact, intermixing of residuals and composite constituents were observed, demonstrating that the Al matrix of the composite also had melted. In all samples examined, cracks were observed to propagate through the eutectic Si network while a small number of broken reinforcement particles were observed. A slight variation in failure mechanisms was observed (e.g., radial, fragmentation, petalling) corresponding to the variation in ductility against high strain rate deformation. In selected specimens, parallel sub-cracks at the exit were observed at 45?? and 30??. These sub-cracks were again filled with intermixed constituents from projectile residuals and composites. This observation suggests that the melting of composite constituents that leads to intermixing occured after the crack propagation and other damage.<br>ID: 030646232; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; On t.p. "p??" is subscript.; Thesis (M.S.M.S.E.)--University of Central Florida, 2011.; Includes bibliographical references (p. 86-88).<br>M.S.M.S.E.<br>Masters<br>Materials Science Engineering<br>Engineering and Computer Science<br>Materials Science and Engineering
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Alawadhi, Meshal Y. "Microstructural evolution and mechanical properties of oxygen-free copper processed by severe plastic deformation." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/415750/.
Full textAbstract:
This thesis presents a study on the microstructural evolution and mechanical properties of oxygen-free copper processed by equal-channel angular pressing (ECAP) and high-pressure torsion (HPT) at room temperature. Experiments were systematically conducted to examine microstructural stability and deformation mechanisms, and their influence on the mechanical properties. A significant grain refinement was attained after deforming the material by 24 passes of ECAP and 10 turns of HPT. The microstructure in the steady-state condition consisted of equiaxed ultrafine grains (UFGs) with high-angles of misorientation. Hardness values increase with increasing number of ECAP passes and HPT turns, and the microhardness distribution was relatively homogenous. ECAP and HPT samples were pulled to failure at room temperature using strain rates of 1.0×10<sup>-4</sup> s<sup>-1</sup>, 1.0×10<sup>-3</sup> s<sup>-1</sup> and 1.0×10<sup>-2</sup> s<sup>-1</sup>. The direct influence of recovery behaviour on the tensile properties was investigated. A simultaneous increase in strength and ductility were observed with increasing number of ECAP passes as well as HPT turns. This is due to occurrence of dynamic recovery at an equivalent strain of ~12 that decreases the total dislocation density and restores the work hardening ability of oxygen-free copper. Both grain boundary and dislocation strengthening mechanisms contribute to the strength of oxygen-free copper. Higher ductility but lower strength was observed when using lower strain rates. UFG copper samples produced by HPT were stored at room temperature for 12 months to investigate microstructural stability and self-annealing phenomena. The results show that the samples processed by a low number of turns exhibit lower thermal stability after storage of 12 months in comparison to the samples processed by a high number of turns. A significant decrease in the hardness was recorded near the edges of the discs processed by 1/4, 1/2 and 1 turn due to recrystallization and grain growth whereas a minor drop in hardness values were observed in the samples processed by 3, 5 and 10 turns, and this drop was related to the recovery mechanism. Tensile tests were repeated after 12 months and the results showed that the ductility was enhanced in compensation for strength. To investigate the deformation mechanism and thermal stability under high strain rates, copper samples were subjected to 1, 4 and 8 passes of ECAP and further deformed by dynamic testing. A significant grain refinement was produced in the ECAP specimens after dynamic testing which is comparable to the grain refinement produced by severe plastic deformation (SPD) techniques such as ECAP and HPT. The grain refinement mechanism was mainly by dislocation slip in the specimen processed by 1 pass whereas it was through dynamic recrystallization for the specimen processed by 8 passes. This is due to the difference in the dislocation densities and stored energy between the ECAP specimens. A 1 pass specimen has better stability than 4 and 8-pass specimens during dynamic testing. It was also shown that increasing the testing temperature and/or the strain rate can highly influence the deformation mechanism.
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Yurkova, A. I., and A. V. Byakova. "Mechanical Properties of Nano- and Submicrocrystalline Iron Subjected to Severe Plastic Deformation by Friction." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35149.
Full textAbstract:
By using nanoindentation technique relationship between microstructure and mechanical parameters
such as nanohardness Hh, plasticity characteristic A, and Young’s modulus E were found to be dependent
on the grain size of the -Fe subjected to severe plastic deformation by friction (SPDF) with argon atmosphere.
Unlike fcc-metals in which the decreasing of grain size to 20 nm results in hardness growth accompanied
by decreasing the plasticity, it was found the reverse effect in bcc-Fe, i.e. decreasing the grain size
from 50 to 20 nm caused the decrease of hardness and increase of plasticity. Moreover, the decrease of
Young’s modulus E with decreasing the grain size down to 20 nm was detected in nanoindentation experiments.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35149
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Tort, Morgan. "The effects of severe plastic deformation on an age hardenable Al-2.5Cu-1.5Mg alloy." Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22578.
Full textAbstract:
Les effets du pressage à canaux égaux (ECAP), un procédé de déformation plastique sévère, ont été examinés dans un alliage Al-2.5Cu-1.5Mg (pourcentage en masse) prône à être durci par traitement thermique et précipitant dans la région α + S. Une multitude de techniques microscopiques, calorimétriques et analytiques ont été utilisés pour caractériser et quantifier les microstructures, incluant la diffraction Kikuchi, la microscopie électronique en transmission, la calorimétrie différentielle à balayage et la sonde atomique tomographique. Quatre différents traitements thermiques initiaux ont été réalisés pour créer quatre microstructures différentes, contenant soit aucun précipités, des clusters Cu-Mg ou/et des composés intermétalliques Al2CuMg. Chaque spécimen a été soumis au procédé ECAP à température ambiante et les effets correspondants sur la microstructure et les propriétés mécaniques ont été analysés. Des expériences en compression pour de petite déformation (inférieures à 7%) ont aussi été entreprises sur les échantillons trempés pour étudier les effets de la compression sur la formation des clusters. Après la trempe et la compression, des clusters Cu-Mg ont été trouvés dans la matrice et il a été élucidé que la formation des clusters était déclenchée par la compression. La fraction volumique des clusters est corrélée directement par la déformation appliquée : plus la déformation est importante, plus la fraction volumique des clusters est importante. Après ECAP, la microstructure est constituée de longues bandes nanocristallines séparée par de gros grains non-déformés pour les échantillons contenant seulement des clusters avant la déformation, tandis que la présence de phase S, avant ECAP, conduit à des microstructures constituées de zones à gros grains et de zones à grains raffinés, distribués d’une façon homogène à travers les échantillons. Bien que les spécimens présentaient clairement des microstructures différentes après ECAP, impliquant que différents mécanismes de renforcement entre en jeux, la limite élastique se situait au-delà de 500 MPa. La limite élastique des échantillons fabriqués par ECAP a été modélisée en superposant les différents mécanismes de renforcement et en saisissant les paramètres microstructurels venant de la caractérisation dans le modèle. Il a été démontré qu’une très bonne corrélation existait entre les limites élastiques provenant du modèle et celles expérimentales<br>The effects of equal channel angular pressing (ECAP), a severe plastic deformation (SPD) technique, were investigated in an age hardenable Al-2.5Cu-1.5Mg (weight percent (wt.%)) alloy precipitating in the α + S phase field. A variety of microscopy, calorimetry and analytical techniques were employed to characterize and quantify the microstructure, including transmission kikuchi diffraction (TKD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and atom probe tomography (APT). Four different initial heat-treatments were conducted to achieve four different microstructures, containing either no precipitates, Cu-Mg clusters or/and Al2CuMg intermetallics. Each specimen was subjected to ECAP at room temperature and the related effects on the microstructure and mechanical properties were analysed. Compression experiments for small strains (less than 7%) were also undertaken on the as-quenched samples to investigate the effects of compression on the formation of clusters.After quenching and compression, Cu-Mg clusters were found in the matrix and it was elucidated that the formation of clusters was triggered by pressing. The volume fraction of clusters was found to be correlated to the strain applied: the higher the strain, the higher the volume fraction.After ECAP, the microstructure was constituted of long nanocrystalline bands separated by large undeformed grains for the samples containing only clusters before deformation, while the presence of S phase, prior to ECAP, lead to microstructures constituted of both coarse and refined zones distributed homogeneously throughout the sample. Although the samples presented clearly different microstructures after ECAP, implying that different strengthening mechanisms were active, the yield strength was found to lie above 500 MPa. The yield strength of the ECAP processed samples was modelled by superposing the different strengthening mechanisms altogether and by inputting the microstructural parameters coming from characterisation in the model. It was demonstrated that a very good correlation existed between the modelled and experimental yield strength values
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Okitsu, Yoshitaka. "FABRICATION OF ULTRAFINE GRAINED STEELS WITHOUT SEVERE PLASTIC DEFORMATION AND THEIR APPLICATION TO AUTOMOBILE BODY STRUCTURES." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157630.
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Chi, Ma. "Improving the Plasticity of Metallic Glass through Heterogeneity Induced by Electropulsing-assisted Surface Severe Plastic Deformation." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555595868348676.
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Jafarian, Hamidreza. "Martensitic Transformation from Ultrafine Grained Meta-stable Austenite in Fe-Ni-C Alloy." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/152514.
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Griffiths, Robert Joseph. "Dynamic and Post-Dynamic Microstructure Evolution in Additive Friction Stir Deposition." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/104664.
Full textAbstract:
Metal additive manufacturing stands poised to disrupt multiple industries with high material use efficiency and complex part production capabilities, however many technologies deposit material with sub-optimal properties, limiting their use. This decrease in performance largely stems from porosity laden parts, and asymmetric solidification-based microstructures. Solid-state additive manufacturing techniques bypass these flaws, using deformation and diffusion phenomena to bond material together layer by layer. Among these techniques, Additive Friction Stir Deposition (AFSD), stands out as unique for its freeform nature, and thermomechanical conditions during material processing. Leveraging its solid-state behavior, optimized microstructures produced by AFSD can reach performance levels near, at, or even above traditionally prepared metals. A strong understanding of the material conditions during AFSD and the phenomena responsible for microstructure evolution. Here we discuss two works aimed at improving the state of knowledge surrounding AFSD, promoting future microstructure optimization. First, a parametric study is performed, finding a wide array of producible microstructures across two material systems. In the second work, a stop-action type experiment is employed to observe the dynamic microstructure evolution across the AFSD material flow pathway, finding specific thermomechanical regimes that occur within. Finally, multiple conventional alloy systems are discussed as their microstructure evolution pertains to AFSD, as well as some more unique systems previously limited to small lab scale techniques, but now producible in bulk due to the additive nature of AFSD.<br>Doctor of Philosophy<br>The microstructure of a material describes the atomic behavior at multiple length scales. In metals this microstructure generally revolves around the behavior of millions of individual crystals of metal combined to form the bulk material. The state and behavior of these crystals and the atoms that make them up influence the strength and usability of the material and can be observed using various high fidelity characterization techniques. In metal additive manufacturing (i.e. 3D printing) the microstructure experiences rapid and severe changes which can alter the final properties of the material, typical to a detrimental effect. Given the other benefits of additive manufacturing such as reduced costs and complex part creation, there is desire to predict and control the microstructure evolution to maximize the usability of printed material. Here, the microstructure evolution in a solid-state metal additive manufacturing, Additive Friction Stir Deposition (AFSD), is investigated for different metal material systems. The solid-state nature of AFSD means no melting of the metal occurs during processing, with deformation forcing material together layer by layer. The conditions experienced by the material during printing are in a thermomechanical regime, with both heating and deformation applied, akin to common blacksmithing. In this work specific microstructure evolution phenomena are discussed for multiple materials, highlighting how AFSD processing can be adjusted to change the resulting microstructure and properties. Additionally, specific AFSD process interactions are studied and described to provide better insight into cumulative microstructure evolution throughout the process. This work provides the groundwork for investigating microstructure evolution in AFSD, as well as evidence and results for a number of popular metal systems.
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Swisher, Douglas Lee. "Production of ultra-fine grains and evolution of grain boundaries during severe plastic deformation of aluminum and its alloys." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA386708.
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Thesis (Degrees of Mechanical Engineer and M.S. in Materials Science and Engineering) Naval Postgraduate School, Dec. 2000.<br>Thesis advisor(s): McNelley, Terry R. "December 2000." Includes bibliographical references (p. 67-69). Also available in print.
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Popov, Mikhail [Verfasser]. "Enhancement of mechanical properties of different magnesium alloys due to grain refinement by severe plastic deformation processing / Mikhail Popov." Clausthal : [Univ.-Bibliothek], 2007. http://d-nb.info/988801175/34.
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Meng, Chenlu Verfasser], Günter [Akademischer Betreuer] Gottstein, and Gerhard [Akademischer Betreuer] [Hirt. "Dynamic strain aging of Al-Mg alloys after severe plastic deformation / Chenlu Meng ; Günter Gottstein, Gerhard Kurt Peter Hirt." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1171905556/34.
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Meng, Chenlu [Verfasser], Günter Akademischer Betreuer] Gottstein, and Gerhard [Akademischer Betreuer] [Hirt. "Dynamic strain aging of Al-Mg alloys after severe plastic deformation / Chenlu Meng ; Günter Gottstein, Gerhard Kurt Peter Hirt." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1171905556/34.
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Rodrigues, Pereira Pedro Henrique. "Microstructural stability and flow properties of an Al-Mg-Sc alloy processed at different temperatures using severe plastic deformation." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/421106/.
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Experiments were systematically conducted to evaluate the thermal stability and flow properties of an Al-3Mg-0.2Sc alloy both without and with processing at different temperatures using equal-channel angular pressing (ECAP) and high-pressure torsion (HPT). The average grain size of the solution treated material was ~300 μm and this was reduced to ~250 nm after 8 passes of ECAP at room temperature (RT). Tests were conducted in both the coarse and ultrafine-grained (UFG) Al alloy to determine the mechanical properties and deformation mechanisms over seven orders of magnitude of strain rate from ~10-4 to ~103 s-1 at 298, 523 and 673 K. The results confirm that there is no apparent breakdown in the Hall-Petch relationship in Al-Mg-Sc alloys with average grain sizes down to ~0.1 μm. Profuse shear banding and grain refinement were observed in the coarse-grained metal during dynamic testing at 4 103 s-1 but in the ECAP-processed alloy there was minor grain coarsening. Dynamic strain ageing occurred in both the coarse and UFG Al-Mg-Sc alloy tested at RT for strain rates below ~10-1 s-1 with a transition in flow mechanism from dislocation climb in the coarse-grained material to superplasticity in the ECAP-processed alloy at 673 K with strain rates from ~10-4 to ~10-2 s-1. After processing through severe plastic deformation (SPD) procedures, samples of the Al alloy were annealed for 1 h at temperatures up to 773 K or mechanical tested at high temperatures using strain rates from 3.3 10-4 to 1 s-1. The microstructural evolution was investigated using advanced techniques such as transmission electron microscopy (TEM), electron backscattered diffraction (EBSD) and X-ray diffraction (XRD). The mechanical properties were assessed through microhardness measurements and tensile testing using miniature specimens having the same dimensions. ECAP processing at 300 K led to higher hardness values and finer grain structures than ECAP at 600 K (~0.60 μm). The alloy processed by ECAP at 600 K exhibited lower driving pressures for grain boundary migration and therefore an improved thermal stability compared with the metal processed at RT. As a result, it displayed larger grain sizes than the alloy processed by ECAP at RT after annealing at T ≥ 623 K. After annealing at 723 and 773 K, the metal processed by ECAP at 300 K displayed a bimodal distribution of grains, whereas samples processed by ECAP at 600 K exhibited uniform microstructures. High superplastic elongations were attained in miniature specimens of the ECAP-processed material when tested at ~523-773 K. However, they were notably lower than after tensile testing using regular ECAP samples. For tests performed at T ≥ 673 K, the alloy processed at 600 K displayed superior superplasticity and it achieved a maximum elongation of ~1490 % after testing at 723 K. Conversely, low temperature superplasticity was obtained at faster deformation rates in samples processed by ECAP at 300 K. HPT processing promotes further hardening and grain refinement in the Al alloy by comparison with ECAP. The HPT-processed samples displayed an average boundary spacing of ~0.15 μm and hardness values of > 180 Hv. The metal processed by HPT at 450 K also exhibited a lower dislocation density of ~7 1012 m-2 and a more uniform microstructure. The microstructural stability was enhanced by conducting HPT processing at 450 K. Although abnormal coarsening was observed in the HPT discs after annealing at 623 and 673 K, the metal processed at 450 K exhibited slower coarsening kinetics and it had grain sizes below 2 μm after annealing at 673 K. After HPT at RT, the Al alloy displayed excellent superplasticity at low homologous temperatures and it achieved a maximum elongation of ~850 % for tests performed at 523 K. However, the overall elongations decreased at T ≥ 623 K and superplasticity was only attained at 673 K using a strain rate of 4.5 10-3 s-1. The Al-3Mg-0.2Sc alloy processed through 10 turns of HPT at 450 K displayed superior superplastic ductilities among all SPD processing conditions. Elongations of > 1100 % were achieved after testing at 673 K using strain rates from 3.3 10-4 to 1.0 10-1 s-1. A record elongation of ~1880 % for HPT-processed metals was attained at 1.5 10-2 s-1 at 673 K. High strain rate superplasticity was also obtained for an extended range of strain rates at temperatures down to 473 K. Analysis of the data confirms a stress exponent of n = 2 for samples of the SPD-processed alloy having elongations of ≥ 400 %. This indicates that superplastic flow by grain boundary sliding is accommodated by dislocation climb in Al-Mg-Sc alloys. The calculated activation energies for superplasticity lie within the range of ~99-125 kJ mol-1 for all processing temperatures and they are higher than the activation energy for grain boundary diffusion in pure Al (~86 kJ mol-1).
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Cao, Yang. "Exploring the Grain Refinement Mechanisms Induced by High-Pressure Torsion Processing." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/9419.
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Severe plastic deformation (SPD) techniques have been used to produce bulk nanostructured metallic materials with superior mechanical properties. Among all SPD techniques, high-pressure torsion (HPT) has been proven the most effective in achieving nanostructures. Therefore, extensive efforts have been devoted to studying HPT processing and its effect on the microstructures and properties of materials. This thesis project is part of an ongoing effort to study HPT and, at the same time, expand our knowledge of SPD. In Chapter 1, extensive literature reviews of SPD, HPT and deformation mechanisms under SPD are provided, and three major issues regarding SPD processing materials are identified. Chapter 2 discusses the choice of a duplex stainless steel as a model material to be processed by HPT. A brief review of duplex stainless steel is given in this chapter. After the choice of material, a review of all the materials characterisation techniques used in this thesis project is presented, as well as details of all the relevant experimental procedures. Chapter 3 describes the plan-views and cross-sectional views of shear strain imposed on austenite/ferrite duplex stainless steel discs at different stages of HPT processing. The effect of the shear strain was correlated to the hardness evolution of the discs. Chapter 4 presents the systematic investigation that was carried out into the microstructure and hardness evolutions of the duplex stainless steel. It was found that the microstructures of both phases of the duplex stainless steel evolved concurrently under continuously increasing shear strain imposed by HPT. Chapter 5 presents a detailed investigation of both cold rolling and HPT caused significant grain refinements to a duplex stainless steel. It was found that while conventional cold rolling of a face-centred cubic structure produces a microstructure with a high density of extended dislocations, increasing the applied stress using HPT gives a nanotwinned coarse-grained structure. In Chapter 6, major conclusions are drawn from this thesis project. Some possible future work is proposed as an extension of the project.
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Khamsuk, Sunisa. "Changes in Microstructure and Mechanical Properties of Aluminum Alloys Heavily Deformed by Torsion." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/180617.
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Mizera, J., P. Maj, and B. Adamczyk-Cieslak. "Comparison of Grain Refinement in Selected Materials Subjected to Hydrostatic Extrusion." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35600.
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The subject of this study was to examine and compare the impact of intense hydrostatic extrusion on grain refinement in three different alloys: duplex stainless steel, commercially used aluminum alloy (6060) and Ag-Cu12 alloy. As a result of the process grain sizes from 370 nm to 90 nm were obtained in aluminum and duplex steel. To analyze the of hydrostatic on mechanical properties tensile tests were also carried out. The highest grain refinement (70 nm) and yield strength increase (over 300%) was observed in duplex steel af-ter hydrostatic extrusion.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35600
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Yapici, Guney Guven. "Investigation and modeling of processing-microstructure-property relations in ultra-fine grained hexagonal close packed materials under strain path changes." Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1578.
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Simon, Anish Abraham. "Shape memory response and microstructural evolution of a severe plastically deformed high temperature shape memory alloy (NiTiHf)." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/3139.
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NiTiHf alloys have attracted considerable attention as potential high temperature Shape Memory Alloy (SMA) but the instability in transformation temperatures and significant irrecoverable strain during thermal cycling under constant stress remains a major concern. The main reason for irrecoverable strain and change in transformation temperatures as a function of thermal cycling can be attributed to dislocation formation due to relatively large volume change during transformation from austenite to martensite. The formation of dislocations decreases the elastic stored energy, and during back transformation a reduced amount of strain is recovered. All these observations can be attributed to relatively soft lattice that cannot accommodate volume change by other means. We have used Equal Channel Angular Extrusion (ECAE), hot rolling and marforming to strengthen the 49.8Ni-42.2Ti-8Hf (in at. %) material and to introduce desired texture to overcome these problems in NiTiHf alloys. ECAE offers the advantage of preserving billet cross-section and the application of various routes, which give us the possibility to introduce various texture components and grain morphologies. ECAE was performed using a die of 90º tool angle and was performed at high temperatures from 500ºC up to 650ºC. All extrusions went well at these temperatures. Minor surface cracks were observed only in the material extruded at 500 °C, possibly due to the non-isothermal nature of the extrusion. It is believed that these surface cracks can be eliminated during isothermal extrusion at this temperature. This result of improved formability of NiTiHf alloy using ECAE is significant because an earlier review of the formability of NiTiHf using 50% rolling reduction concluded that the minimum temperature for rolling NiTi12%Hf alloy without cracks is 700°C. The strain level imposed during one 90° ECAE pass is equivalent to 69% rolling reduction. Subsequent to ECAE processing, a reduction in irrecoverable strain from 0.6% to 0.21% and an increase in transformation strain from 1.25% to 2.18% were observed at a load of 100 MPa as compared to the homogenized material. The present results show that the ECAE process permits the strengthening of the material by work hardening, grain size reduction, homogeneous distribution of fine precipitates, and the introduction of texture in the material. These four factors contribute in the increase of stability of the material. In this thesis I will be discussing the improvement of mechanical behavior and stability of the material achieved after various passes of ECAE.
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Bayramoglu, Sadik. "Characterization Of Ultra-fine Grained Steel Samples Produced By High Pressure Torsion Via Magnetic Barkhausen Noise Analysis." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610637/index.pdf.
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High Pressure Torsion (HPT) is one of the most widely used severe plastic deformation methods which enable to obtain a crack free ultra-fine grained bulk material with improved mechanical properties like increased strength and toughness. In the process, a disc shaped sample is pressed between two anvils and deformed via surface friction forces by rotating one of the anvils. The aim of this study is to nondestructively characterize the variations in the deformation uniformity of the severely deformed steel disks. Two sets of low carbon steel samples were obtained by applying the unconstrained and constrained HPT process up to 6 turns. Magnetic Barkhausen Noise (MBN) method was used in order to evaluate the samples in a nondestructive manner via a commercial device. The results of the MBN measurements were verified with those of conventional methods such as<br>x-ray diffraction (XRD), metallographic examination and hardness measurements. The initial stages of HPT revealed the effects of conventional plastic deformation on MBN<br>however with further straining, grain size refinement prevailed and caused increase in MBN signals.
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Borhani, Ehsan. "Microstructure and Mechanical Property of Heavily Deformed Al-Sc Alloy Having Different Starting Microstructures." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/152522.
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Görtan, Mehmet Okan [Verfasser], Peter [Akademischer Betreuer] Groche, and Clemens [Akademischer Betreuer] Müller. "Severe plastic deformation of metallic materials by equal channel angular swaging: Theory, experiment and numerical simulation / Mehmet Okan Görtan. Betreuer: Peter Groche ; Clemens Müller." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2014. http://d-nb.info/1110902077/34.
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May, Lilia. "Mechanical properties of ultrafine-grained Ti-6Al-4V ELI alloy processed by severe plastic deformation = (Mechanische Eigenschaften einer ultrafeinkörnigen TiAl6V4-ELI-Legierung hergestellt mittels Hochverformung)." kostenfrei, 2009. http://d-nb.info/999601946/34.
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Martin, Castillo Morales. "Examining the effects of ultrasonic impact treatment as a severe plastic deformation process on the fatigue behaviour of 2024-T3 and T150-T651 aluminium alloys." Thesis, University of Sheffield, 2008. http://etheses.whiterose.ac.uk/6106/.
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Aluminium alloys are widely used in aerospace vehicles which are under cyclic loads through their operation. The loads may cause detrimental changes in material structure being more prone to crack initiation, starting a potential process of failure for the structure. In this research the effects of fatigue damage are assessed for two aluminium alloys, 2024-T3 and 7150-T561, after using a surface engineering method which uses the plastic deformation on the surface, like many others, to extend (or reduce) the fatigue life of materials.
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ムハマド, リファイ, and Muhammad Rifai. "Mechanical and corrosion properties of ultrafine-grained low C, N Fe-20%Cr steel produced by equal channel angular pressing." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12902984/?lang=0, 2015. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12902984/?lang=0.
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Equal-channel angular pressing (ECAP) is one of the severe plastic deformation (SPD) to produce ultra-fine grain (UFG) material, and its principle and microstructural developments. The majority of papers on SPD materials have been devoted to the face centered cubic (FCC) structure materials such as Al, Cu and Ni. The UFG of high alloy ECAP processing has been difficult up to now, but we were successful in this study. Fe-20%Cr steel with extremely low C and N has different slip behavior from the FCC. The mechanical properties and corrosion resistance were investigated in term microstructural evolution during ECAP processing.<br>博士(工学)<br>Doctor of Philosophy in Engineering<br>同志社大学<br>Doshisha University
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Kadri, Shabibahmed Jehangir. "Microstructural breakdown and scale-up effects in equal channel angular extrusion of cast copper." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4341.
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The primary objectives of this study were: (1) to verify the effectiveness of ECAE
to induce equal amounts of strain and grain refinement in bars of different cross-sectional
areas, (2) to determine the effectiveness of ECAE in breaking down the as-cast
macrostructure in CDA 101 Cu and in producing a homogeneous material containing
micron-scale grains upon recrystallization, and (3) to determine a thermomechanical
processing (TMP) schedule (from the ones examined) that produces the best
microstructure in terms of grain size and uniformity. The effects of extrus ion route, levels
of strain and intermediate heat treatment were investigated.
To achieve the first objective, bars having square cross-sections of three different
sizes, 19 mm, 25 mm and 50 mm, were processed up to eight ECAE passes through
routes A, B, C and E. To achieve the second and third objectives, bars were processed up
to eight ECAE passes with and without intermediate heat treatments through routes Bc,
C, E and F. ECAE processing was carried out in a 90o extrusion die with sliding walls at
an extrusion speed of 2.5 mm/s. Recrystallization studies were carried out on the
processed material to evaluate the recrystallization behavior and thermal stability of the
material. The as-worked and recrystallized materials were characterized by Vickers
microhardness, optical microscopy (OM) and transmission electron microscopy (TEM).
Results indicate that similar hardness values, sub-grain morphology and
recrystallized grain size are generated in the three bars having different cross-sectional
sizes processed through ECAE. ECAE is shown to induce uniform strain in all three billet
sizes. ECAE is therefore shown to be effective in scale-up to a size of at least 50 mm,
with larger billets giving better load efficiency. Results from the later parts of this study indicate that eight extrusion passes via
route Bc produces the best microstructure in terms of grain size and microstructural
uniformity. The routes can be arranged in the sequence Bc> E, F> C for their ability to
produce a uniform recrystallized microstructure with small average grain size.
Macroscopic shear bands are sometimes generated during extrusion depending upon the
initial grain morphology and texture of the material.
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Subbarayan, Sapthagireesh. "Fabrication of a Novel Al/Mg Composite: : Processing and Characterization of Pure Aluminium, Al/AZ31 Alloy Bi-Metal and Aluminium based Sheet Composites by Severe Plastic Deformation." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23778.
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Bernardi, Heide Heloise. "Processamento e caracterização microestrutural de nióbio deformado plasticamente por extrusão em canal angular." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/97/97134/tde-27092012-123519/.
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Amostras de nióbio de alta pureza na forma de monocristais, bicristais e policristais foram retiradas de seções longitudinais de lingotes fundidos por feixe eletrônico. As amostras foram deformadas via extrusão em canal angular (ECAE - Equal Channel Angular Extrusion) em temperatura ambiente até 8 passes, utilizando a rota Bc numa matriz com ângulo de intersecção entre os canais de  = 90º. As amostras foram caracterizadas em termos da evolução microestrutural e da textura de deformação. A caracterização microestrutural foi realizada com o auxílio de microscopias ótica, eletrônica de varredura e eletrônica de transmissão, além de medidas de difração de elétrons retroespalhados (EBSD) para determinação da microtextura e da mesotextura. Medidas de microdureza Vickers foram realizadas para acompanhar o encruamento e o amolecimento das amostras. Um outro monocristal de nióbio foi deformado em 1 passe via ensaio interrompido, utilizando uma matriz com ângulo  = 120º, a fim de estudar a evolução da textura durante a passagem pelo canal de ECAE. A textura foi determinada por meio de difração de raios X e comparada com os dados da literatura para materiais deformados via ECAE com estrutura CCC e também com as texturas simuladas pelo modelo VPSC (visco-plastic self-consistent). No estudo comparativo numa escala maior (monocristal e policristal), verificou-se que houve um refinamento microestrutural significativo após 8 passes. O espaçamento médio entre os contornos de alto ângulo medido perpendicular à direção de extrusão foi próximo nos dois casos (500 nm), maior que o observado para o monocristal deformado numa escala menor (440 nm). Os resultados mostram ainda que os grãos do policristal deformado são mais equiaxiais que os do monocristal. Amostras foram recozidas isotermicamente para avaliar o comportamento frente ao engrossamento microestrutural. Os resultados mostram que o engrossamento torna-se apreciável, em geral, a partir de 500oC com a ocorrência de recristalização descontínua. Acima de 700oC, o crescimento normal de grão passa a ser o principal mecanismo de engrossamento microestrutural. Efeitos de orientação importantes foram observados no bicristal nos estados encruado e recozido.<br>High-purity niobium single crystals, bicrystals and polycrystals were cut out from longitudinal sections of ingots processed by electron beam melting. Samples were deformed by Equal Angular Channel Extrusion (ECAE) at room temperature up to 8 passes, using the route Bc with a die angle  = 90o. Samples were characterized in terms of their microstructural evolution and deformation textures. Microstructural characterization was performed using optical, scanning electron, and transmission electron microscopies, as well as electron-backscatter diffraction measurements (EBSD) to determine both microtexture and mesotexture. Vickers microhardness testing was performed to follow hardening and softening behaviors in the samples. Another single crystal was deformed by 1 pass in an interrupted ECAE experiment using a die angle  = 120o to follow the changes in texture through the extrusion channel. Texture was determined by X ray diffraction and compared with those reported in the literature for deformed bcc materials and also with those predicted using the viscoplastic self-consistent model (VPSC). A comparative study in a larger scale (single and polycrystals) was also performed. It was observed that there is a significant refinement of the microstructure after 8 passes. The average spacing between high angle boundaries perpendicular to extrusion direction was close in the two cases (500 nm), larger than observed in the single crystal deformed in a smaller scale (440 nm). Results also show that ultrafine grains of the deformed polycrystal are more equiaxial compared to those found in the deformed single crystal. Samples were annealed to evaluate their behavior regarding microstructural coarsening. Results show that coarsening becomes noticeable at temperatures higher than 500oC by means of discontinuous recrystallization. Above 700oC, normal grain growth becomes the main microstructure coarsening mechanism. Important orientation effects were observed in the bicrystal in both deformed and annealed states.
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Cakmak, Gulhan. "The Processing Of Mg-ti Powder For Hydrogen Storage." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613102/index.pdf.
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A study was carried out on the selection of processing condition that would yield Mg-Ti with most favourable hydrogenation properties. Processing routes under consideration were<br>mechanical milling under inert atmosphere, reactive milling i.e. milling under hydrogen atmosphere, ECAP (equal channel angular pressing) and thermal plasma synthesis. Structure resulting from each of these processing routes was characterized with respect to size reduction, coherently diffracting volume and the distribution of Ti catalyst.
Mechanical milling yielded a particulate structure made up of large Mg agglomerates with embedded Ti fragments with a uniform distribution. Mg agglomerates have sizes larger than 100 µ<br>m which arises as a result of a balance between cold welding process and ductile fracture. Repeated folding of Mg particles entraps Ti fragments inside the Mg agglomerates resulting in a very uniform distribution. Coherently diffracting volumes measured by X-ray Rietveld analysis have small sizes ca. 26 nm which implies that the agglomerates typically comprise 1011 crystallites. Mechanical milling under hydrogen, i.e. reactive milling, led to drastic reduction in particle size. Mg and Ti convert to MgH2 and TiH2 which are milled efficiently due to their brittleness resulting in particle sizes of sub-micron range. Hydrogenation experiments carried out on Mg-10 vol % Ti milled under argon yields enthalpy and entropy values of -76.74 kJ/mol-H2 and -138.64 J/K.mol-H2 for absorption and 66.54 kJ/mol H2 and 120.12 J/K.mol H2 for desorption, respectively. For 1 bar of hydrogen pressure, this corresponds to a hydrogen release temperature of 280 °<br>C. This value is not far off the lowest desorption temperature reported for powder processed Mg based alloys.
ECAP processing is a bulk process where the powders, consolidated in the first pass, have limited contact with atmosphere. This process which can be repeated many times lead to structural evolution similar to that of milling, but for efficient mixing of phases it was necessary to employ multi-pass deformation. An advantage of ECAP deformation is strain hardening of the consolidated powders which has improved milling ability. Based on this, a new route was proposed for the processing of ductile hydrogen storage alloys. This involves several passes of ECAP deformation carried out in open atmosphere and a final milling operation of short duration under inert atmosphere.
The plasma processing yields Mg particles of extremely small size. Evaporation of Mg-Ti powder mixture and the subsequent condensation process yield Mg particles which are less than 100 nm. Ti particles, under the current experimental condition used, have irregular size distribution but some could be quite small, i.e. in the order of a few tens of nanometers.
Of the four processing routes, it was concluded that both reactive milling and thermal plasma processing are well suited for the production of hydrogen storage alloys. Reactive milling yield particles in submicron range and plasma processing seems to be capable of yielding nanosize Mg particles which, potentially, could be decorated with even smaller Ti particles.
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Uzuncakmak, Gokturk Emre. "Design And Production Of A Dissimilar Channel Angular Pressing System To Obtain High Strength Aluminum Alloy Sheets." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610609/index.pdf.
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The aim of this thesis work is to design and manufacture a Dissimilar Channel Angular Pressing (DCAP) system for severe plastic deformation of aluminum alloy sheets in order to obtain ultra-fine grained structure. First, a DCAP system was designed by Finite Element Analysis and constructed after various optimization trials. Next, 6061-T0 aluminum alloy plates were severely deformed by various DCAP passes through the system. The samples were characterized by metallography, X-ray diffraction, tension and hardness tests. It has been observed that the yield strength was improved about 100 % after 2 DCAP passes, and 45 nm sub-grain size was obtained.
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Marko, Vilotić. "Intenzivna plastična deformacija u procesima višefaznog sabijanja materijala." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2015. http://www.cris.uns.ac.rs/record.jsf?recordId=95538&source=NDLTD&language=en.
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Predstavljena je nova metoda intenzivne plastične deformacije – višefazno sabijanje V-alatom. Koristeći ovu metodu, sabijanjem u osamnaest faza, unapređene su mehaničke osobine niskougljeničnog čelika Č.1221 – tvrdoća, čvrstoća i deformabilnost. Za ispitivanje mikrostrukture korišćeni su svetlosni, skening i transmisioni mikroskop. Prosečna veličina kristalnog zrna početnog materijala od 19 mikrometara je smanjena na 250 nanometara nakon dvanaest faza sabijanja. Nakon osamnaest faza sabijanja na čelu uzorka ostvarena je ukupna deformacija u iznosu od 3,38.<br>A new severe plastic deformation method has been presented - multistage upsetting by V-shape dies. By using this method, in eighteen upsetting stages, mechanical propreties (hardness, strenght and formability) of C15E low carbon steel has been improved. For microstructure analysis light, scanning and transmission microscopes have been employed. Initial average grain size of 19 μm has been reduced to 250 nm after twelve upsetting stages. After eighteen upsetting stages, total effective deformation at the sample forehead of 3,38 has been obtained.