To see the other types of publications on this topic, follow the link: Equal Channel Angular Pressing (ecap).
Dissertations / Theses on the topic 'Equal Channel Angular Pressing (ecap)'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 45 dissertations / theses for your research on the topic 'Equal Channel Angular Pressing (ecap).'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Hellmig, Ralph Jörg [Verfasser]. "Hochgradige plastische Umformung durch Equal channel angular pressing (ECAP) / Ralph Jörg Hellmig." Clausthal : [Univ.-Bibliothek], 2008. http://d-nb.info/989657752/34.
Full text
2
Werenskiold, Jens Christofer. "Equal channel angular pressing (ECAP) of AA6082 : mechanical properties, texture and microstructural development." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Natural Sciences and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-894.
Full textAbstract:
<p>This thesis deals with the concept of ECAP applied to a commercial Al Mg-Si alloy (AA6082.50). A detailed analysis of the strains introduced by ECAP in a single passage through the die has been made, based on direct measurements on partially pressed samples. </p><p>Further, the mechanical properties of ECAP’ed samples have been investigated. The effect of initial material temper and post-ECAP artificial aging was investigated in addition to the effect of strain accumulation and processing route.</p><p> Finally, a detailed study of the textural and microstructural development was made. The continuous evolution of texture and microstructure was followed through the ECAP deformation zone up to an accumulated strain of 2 (2 passes) by route A, and linked to strain measurements from the same zone. </p><p>Strain measurements on sectioned samples have validated the plane strain assumption for ECAP. The shear angle has been measured and some typical features of ECAP have been corroborated, i.e. friction and material temper affect the strain distribution, the strain homogeneity and the workpiece corner angle, friction being the most significant here. Also, new conclusions have been drawn. The analysis of material element deformation histories along path lines reveals that ECAP can be interpreted as the combination of shearing and stretching (i.e. tension and/or compression). Furthermore, the final shear strain angle obtained in ECAP appears to be friction and material temper independent in the zone of homogeneous deformation. </p><p>The 6082 alloy has been successfully processed by ECAP at room temperature to strains ε =6 to ε =8. The alloy has been pressed in the solutionized, T4, homogenized and soft annealed states. The highest tensile strength was obtained from the solutionized material, followed by T4, homogenized and soft annealed. This behaviour is linked to the solid solution content prior to ECAP and the potential for dynamic precipitation during ECAP processing.</p><p> The tensile elongation to failure drops to a constant level between 4% and 9% after ECAP and is highest for the soft annealed and lowest for the solutionized material. The ductility in the solutionized material can, however, recover to ~18% elongation to failure (i.e. an increase by a factor 2-3) by low temperature heat treatment with only a small drop in tensile strength. </p><p>Soft annealed and ECAP’ed material has been compared to cold rolling to similar strains. The tensile strength response to accumulated strain is similar, but the ductility and post uniform deformation is different. However, the ECAP’ed material can be processed to higher strains and, thus, achieving higher strength. </p><p>The tensile yield strength behaviour of the homogenized and ECAP’ed material can be described by a simple relation to the grain size and the fraction high and low angle boundaries.</p><p> The typical texture components related to ECAP of aluminium, pressed by route A, have been identified. The typical ECAP texture starts to develop already at ~25% strain and increases in intensity during the first pass. In the second pass, two of the stable texture components continue to increase in intensity, while the other texture components decrease.</p><p> The microstructural development during the first pass is dominated by deformation banding leading to grain-subdivision. The average linear intercept distance (grain size) is reduced from ~80μm to ~4μm for high angle boundaries and from ~10μm to ~0.7μm for low angle boundaries.</p><p>During the second pass, the linear intercept distance is further reduced to ~1.8μm for high angle and ~0.3μm for low angle boundaries. Deformation twins are observed during the second pass and are believed to play an important role in severe plastic deformation when the grains reach the sub-micron or nano-metre scale.</p><p>The deformation banding have been explained in terms of the low energy dislocation structure (LEDS) theory, and has been shown to be an important mechanism in the early stages of grain subdivision, and is further believed to be the main source of high angle grain boundary formation by grain subdivision down to a grain size of approximately ~0 6μm, when other deformation mechanisms may be energetically more favourable.</p>
3
Houston, Katrina M. "Effects of strain path on the microstructure of aluminum alloys during Equal Channel Angular Pressing (ECAP)." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Dec%5FHouston.pdf.
Full textAbstract:
Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2007.<br>Thesis Advisor(s): McNelley, Terry. "December 2007." Description based on title screen as viewed on January 18, 2008. Includes bibliographical references (p. 53-55). Also available in print.
4
Silva, Gilson Jr. "Estudo da influência do processo ECAP (Equal Channel Angular Pressing) nas propriedades mecânicas e características microestruturais do aço SAE 1020." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/152335.
Full textAbstract:
Submitted by GILSON SILVA JUNIOR null (gilson_feg@yahoo.com.br) on 2017-12-18T12:27:06Z
No. of bitstreams: 1
Tese Doutorado Defesa - Versão Final.pdf: 8602731 bytes, checksum: 8f3cbfc632bdb7f8998d8a2a7aa87243 (MD5)<br>Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2017-12-18T13:21:51Z (GMT) No. of bitstreams: 1
silvajunior_g_dr_guara.pdf: 8602731 bytes, checksum: 8f3cbfc632bdb7f8998d8a2a7aa87243 (MD5)<br>Made available in DSpace on 2017-12-18T13:21:51Z (GMT). No. of bitstreams: 1
silvajunior_g_dr_guara.pdf: 8602731 bytes, checksum: 8f3cbfc632bdb7f8998d8a2a7aa87243 (MD5)
Previous issue date: 2017-11-10<br>A obtenção de granulometria ultrafina em aços com baixo teor de carbono pode contribuir para ampliação de suas aplicações na indústria, devido as propriedades mecânicas superiores que podem ser alcançadas com o refinamento de grãos, tais como: resistência mecânica, dureza, e tenacidade. O processo conhecido como Equal Channel Angular Pressing (ECAP) induz deformações plásticas severas suficientes para alterar as características microestruturais dos metais reduzindo seu tamanho de grão, e consequentemente melhorando algumas propriedades mecânicas, sem alterar a composição química dos materiais, ao utilizar temperaturas abaixo do ponto de recristalização dos metais. Neste trabalho o processo ECAP foi conduzido com corpos de prova na temperatura de 550°C utilizando como material de estudo aço SAE 1020. Os corpos de prova foram separados em três grupos. No primeiro grupo as amostras não foram submetidas a nenhum tratamento térmico entre os passes, no segundo grupo foi aplicado tratamento de alívio de tensões após os passes, e por fim, no terceiro grupo e foi aplicado um tratamento de recozimento intercrítico após o primeiro passe. Ensaios mecânicos de tração, dureza e charpy foram realizados com objetivo de verificar a influência do processo ECAP no comportamento mecânico do aço. Com intuito de verificar as alterações microestruturais causadas pelo processo ECAP foram utilizadas as técnicas de microscopia óptica e eletrônica de varredura. O trabalho tem como objetivo principal induzir o refinamento dos grãos por meio do processo ECAP em matriz bipartida elaborada neste trabalho. Os resultados das análises microestruturais e dos ensaios mecânicos demonstraram que os tratamentos térmicos utilizados combinados ao processo ECAP influenciaram diretamente no comportamento do aço SAE 1020. Conforme o número de passes pela matriz ECAP ocorreu uma redução do tamanho dos grãos, assim como aumento do limite de resistência a tração e dureza do aço 1020. Com relação ao tratamento térmico de alívio de tensão, uma melhor combinação entre resistência mecânica e ductilidade foi encontrada. O tratamento de recozimento intercrítico foi suficiente para induzir a transformação de fases no aço SAE 1020, o qual proporcionou resultados positivo no que diz respeito a ductilidade e resistência mecânica. Por fim, a consistência das investigações da evolução microestrutural permitiu compreender os efeitos do ECAP no aço SAE 1020.<br>Ultrafine grained microstructures obtaining in low carbon steels may contribute to enlarge the application of this material in industry, due to superior properties that can be achieved, such as: mechanical strength, hardness, and toughness. The process known as Equal Channel Angular Pressing (ECAP) induces severe plastic deformation sufficient to modify metals microstructures characteristics, reducing its grains size, and consequently improve its mechanical properties without materials chemistry composition changes, under temperatures below to recrystallization point. At this work ECAP process was carried out with specimens at 550° C using steel SAE 1020 as material. The specimens were divided into three groups. The specimens in the first group none heat treatment was applied between and after ECAP passes, in the second group the specimens were submitted under stress relief heat treatment after ECAP passes, and in the third group, specimens were submitted under intercritical annealing after first pass. Mechanical tensile strength, hardness and charpy impact tests were used with aim to verify the ECAP influence in steel mechanical behavior. In order to verify microstructures evolution caused by ECAP were applied optical and scanning electron microscopy. The aim of this work is grain refining by means of ECAP process with two parts tool elaborated in this study. The microstructure analysis and mechanical tests results shown that the heat treatments applied, combined with ECAP process directly influenced on steel SAE 1020 behavior. According to the number of passes grains sizes were reduced, as well the ultima tensile strength and hardness were increased. In reference of stress relief heat treatment, better combination between mechanical strength and ductility was achieved. Intercritical annealing treatment was capable to induce phase transformation in steel SAE 1020, which provided positive results with respect to ductility and mechanical strength. In conclusion, the consistence of microstructure evolution investigation became possible to understand effects of ECAP in steel SAE 1020
5
Silva, Junior Gilson. "Estudo da influência do processo ECAP (Equal Channel Angular Pressing) nas propriedades mecânicas e características microestruturais do aço SAE 1020 /." Guaratinguetá, 2017. http://hdl.handle.net/11449/152335.
Full textAbstract:
Orientador: Angelo Caporalli Filho<br>Banca: Marcelo dos Santos Pereira<br>Banca: Ana Paula Rosifini Alves Claro<br>Banca: Karia Regina Cadorso<br>Banca: Mirian de Lourdes Noronha Motta Melo<br>Resumo: A obtenção de granulometria ultrafina em aços com baixo teor de carbono pode contribuir para ampliação de suas aplicações na indústria, devido as propriedades mecânicas superiores que podem ser alcançadas com o refinamento de grãos, tais como: resistência mecânica, dureza, e tenacidade. O processo conhecido como Equal Channel Angular Pressing (ECAP) induz deformações plásticas severas suficientes para alterar as características microestruturais dos metais reduzindo seu tamanho de grão, e consequentemente melhorando algumas propriedades mecânicas, sem alterar a composição química dos materiais, ao utilizar temperaturas abaixo do ponto de recristalização dos metais. Neste trabalho o processo ECAP foi conduzido com corpos de prova na temperatura de 550°C utilizando como material de estudo aço SAE 1020. Os corpos de prova foram separados em três grupos. No primeiro grupo as amostras não foram submetidas a nenhum tratamento térmico entre os passes, no segundo grupo foi aplicado tratamento de alívio de tensões após os passes, e por fim, no terceiro grupo e foi aplicado um tratamento de recozimento intercrítico após o primeiro passe. Ensaios mecânicos de tração, dureza e charpy foram realizados com objetivo de verificar a influência do processo ECAP no comportamento mecânico do aço. Com intuito de verificar as alterações microestruturais causadas pelo processo ECAP foram utilizadas as técnicas de microscopia óptica e eletrônica de varredura. O trabalho tem como objetivo principal in... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: Ultrafine grained microstructures obtaining in low carbon steels may contribute to enlarge the application of this material in industry, due to superior properties that can be achieved, such as: mechanical strength, hardness, and toughness. The process known as Equal Channel Angular Pressing (ECAP) induces severe plastic deformation sufficient to modify metals microstructures characteristics, reducing its grains size, and consequently improve its mechanical properties without materials chemistry composition changes, under temperatures below to recrystallization point. At this work ECAP process was carried out with specimens at 550° C using steel SAE 1020 as material. The specimens were divided into three groups. The specimens in the first group none heat treatment was applied between and after ECAP passes, in the second group the specimens were submitted under stress relief heat treatment after ECAP passes, and in the third group, specimens were submitted under intercritical annealing after first pass. Mechanical tensile strength, hardness and charpy impact tests were used with aim to verify the ECAP influence in steel mechanical behavior. In order to verify microstructures evolution caused by ECAP were applied optical and scanning electron microscopy. The aim of this work is grain refining by means of ECAP process with two parts tool elaborated in this study. The microstructure analysis and mechanical tests results shown that the heat treatments applied, combined with ECAP p... (Complete abstract click electronic access below)<br>Doutor
6
Qarni, Muhammad Jawad. "Effect of incremental equal channel angular pressing (I-ECAP) on the microstructural characteristics and mechanical behaviour of commercially pure titanium." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28410.
Full textAbstract:
Owing to its high specific strength, low density, outstanding corrosion resistance and excellent bio-compatibility titanium and its alloys are a material of choice in many aerospace, military, chemical and biomedical applications. Ti-6Al-4V is the most widely used alloy for medical device applications such as in total replacement implants, where higher strength characteristics are generally a requirement. However, research has suggested that alloying elements such as aluminium and vanadium present in that alloy can be toxic in the long term and are therefore undesirable for full bio-integration. Commercially pure titanium (CP-Ti) has superior biocompatibility but it lacks the strength required for most load bearing implants. One viable solution is to abandon the use of alloying elements and to improve the mechanical strength and performance of CP-Ti by nano-structuring or grain refinement. Severe plastic deformation (SPD) is an established method for introducing extreme grain refinement in metals. The technique imparts high plastic strain to the material without significantly changing the sample dimensions and is capable of achieving ultrafine grain (UFG) structure in metals. UFG materials are characterized by an average grain size of < 1 μm and with mostly high angle grain boundaries. These materials exhibit exceptional improvements in strength, superplastic behaviour and in case for titanium, improved corrosion resistance and enhanced biocompatibility. Among the various available SPD methods, equal channel angular pressing (ECAP) is the most widely used method for obtaining bulk UFG materials. However, ECAP (in its classical form) suffers from low productivity and is not a practical option for commercialization. Therefore, lately the interest is in the development of continuous SPD techniques, capable of processing very long or continuous billets for use in commercial applications. Incremental ECAP (I-ECAP) developed at the University of Strathclyde, offers such possibility. This promising technique has a strong potential of obtaining the much-needed high strength CP-Ti for biomedical implants on an industrial scale. The aim of the present research work is to investigate the feasibility of the I-ECAP process in improving the mechanical performance of CP-Ti by refining its grain structure. However, before processing CP-Ti on the I-ECAP experimental rig, it was necessary to eliminate the some existing limitations of the rig and improve the overall process efficiency. Major upgrades and enhancements were implemented as part of the present work. These include: automation of material feeding system, elevated temperature capability, press controller upgrade, data acquisition and process control during experiments. Moreover, finite element analysis was performed to optimize the tooling geometry by studying the billet deformation behaviour and subsequently new I-ECAP dies were designed and manufactured suitable for processing CP-Ti billets. Using the considerably improved I-ECAP experimental facility, CP-Ti billets were subjected to multiple passes of the I-ECAP process at elevated temperatures. To investigate the effect of different levels of induced shear strain per pass, billets were processed using two separate dies with channel intersection angles of 120 and 90°. Microstructural evolution and textural development in the material was tracked and examined using high-resolution electron backscatter diffraction (EBSD) technique. Twinning and continuous dynamic recrystallization (CDRX) have been observed to act as a grain refinement mechanism during subsequent passes of I-ECAP. Analysis of the microstructure shows that UFG structure was successfully obtained with mostly high angle grain boundaries (HAGB) in the processed billets using the two dies. Room temperature tensile tests carried out before and after processing show significant increase in strength with some loss in ductility in the processed material. The yield strength and ultimate tensile strength (UTS) of the material after I-ECAP processing using the die angle of 120° was increased by 81% and 25%, respectively. The material processed using the die angle of 90° exhibits an even higher increase in yield strength and UTS i.e. 118% and 33%, respectively. Compression tests conducted at different strain rates at room temperature show increase in strength with a three stage hardening behaviour, though the severely deformed UFG material suffers a loss in its strain hardening ability. Detailed microhardness measurements also show the increase in hardness after processing with a reasonable level of homogeneity. Finally, workability characteristics of UFG titanium is determined by compression testing at room and warm temperature conditions (400 to 600 °C). The work has successfully demonstrated that I-ECAP process is effective in improving the mechanical performance of titanium and has a potential for commercialization.
7
Hockauf, Matthias. "Fließspannungsverhalten ultrafeinkörniger Aluminiumwerkstoffe unter besonderer Berücksichtigung der Dehnrate." Doctoral thesis, Universitätsbibliothek Chemnitz, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200901887.
Full textAbstract:
Aufgrund ihrer herausragenden Eigenschaften haben ultrafeinkörnige Werkstoffe, die aus konventionellen normalkörnigen Halbzeugen über eine extrem große Kaltverformung hergestellt wurden, in den letzten zwei Jahrzehnten zunehmend an Bedeutung erlangt. In der vorliegenden Arbeit wird das Fließspannungsverhalten eines Reinaluminiumwerkstoffes (EN AW-1070 – Al99,7) und einer ausscheidungshärtbaren Aluminiumlegierung (EN AW-6060 – AlMgSi) mit Korngrößen von bis zu 660 nm und 310 nm in einem weiten Bereich von Dehnungen und Dehnraten analysiert und mit den zzt. existierenden Modellvorstellungen zu den mikrostrukturellen Abläufen in Verbindung gebracht. Um die Voraussetzung zur Herstellung von ultrafeinkörnigen Werkstoffen zu schaffen, wurden mehrere Werkzeugprototypen für die ECAP-Umformung im Labormaßstab entwickelt und erprobt. Die Untersuchungen zum Fließspannungsverhalten erfolgten anhand von Zug- und Druckversuchen über insgesamt sieben Dekaden der Dehnrate bis in den Bereich der hochdynamischen Belastung von 10^3 s^-1. Die Tests zeigen, dass das Fließspannungsverhalten ultrafeinkörniger Aluminiumwerkstoffe vollständig mithilfe der thermisch aktivierbaren Mechanismen erklärbar ist, wobei Ausscheidungen eine wichtige Rolle spielen<br>Because of their exceptional properties ultrafine-grained materials, processed from conventional polycrystalline materials by severe plastic deformation, have gained increasing scientific and industrial interest during the last two decades. Based on the concept of work-hardening for f.c.c. metals the commercially pure aluminium AA1070 (Al99,7 – soft annealed) and the aluminium alloy AA6060 (AlMgSi – peak aged) were investigated. ECAP was used to introduce very high strains and an ultrafine-grained microstructure with grain sizes down to 660 nm and 310 nm. Subsequently compression and tensile tests were performed in a wide range of strain rates over seven decades up to the range of impact loading of 10^3 s^-1. The results indicate that strain path and the corresponding dislocation structure is important for the post-ECAP yielding and the following hardening response. Furthermore the precipitates of the AA6060 clearly constrain the interactions of dislocations in work-hardening stage III – causing lower strain rate sensitivity. If compared to the AA1070 they avoid hardening in stage V where an additional rate and temperature depending effect contributes – caused by the interaction of deformation induced vacancies and dislocations. The results indicate that the strain-hardening behavior can be described by thermal activated mechanisms
8
Suh, Joung Sik Verfasser], Wolfram [Akademischer Betreuer] Volk, and A. Erman [Akademischer Betreuer] [Tekkaya. "Improvement in Cold Formability of AZ31 Magnesium Alloy Sheets Processed by Equal Channel Angular Pressing (ECAP) / Joung Sik Suh. Betreuer: Wolfram Volk. Gutachter: Wolfram Volk ; A. Erman Tekkaya." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1081488247/34.
Full text
9
Bardet, Matthieu. "Elaboration de matériaux composites à matric Titane et à nano-renforts TiC et TiB par différents procédés de métallurgie des poudres : frittage par hydruration/dehydruration et déformation plastique sévère (Equal Channel Angular Pressing (ECAP))." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0026/document.
Full textAbstract:
Les composites à matrice Titane avec des renforts nanométriques présente des améliorations intéressantes quant aux propriétés mécaniques, sans affecter la ductilitédu matériau. Ce travail de thèse se concentre sur l’élaboration et la caractérisation dematériaux composites de Titane obtenus par deux différents procédés de métallurgie despoudres : La densification par déformation plastique sévère utilisant l’ECAP (Equal ChannelAngular Pressing) et les procédés de frittage par hydrogénation/déshydrogénation (HDH).L’ECAP est un procédé de densification rapide utilisant la déformation plastique desmatériaux, se faisant à relativement basse température. Les procédés HDH utilisent ladéshydrogénation du titane comme un levier sur les mécanismes de frittage. Les différentsnano-renforts utilisés dans ces travaux sont les particules sphériques de TiC et les aiguillesde TiB. Cette étude montre l’influence de la nature et de la forme des renforts, ainsi que duprocédé de métallurgie des poudres utilisé, sur les propriétés et la microstructure final desmatériaux denses<br>Titanium based composites using nano-sized reinforcements are goodcandidates for the improvement in mechanical properties without affecting ductility. Thisstudy is dedicated to fabrication and characterisation of Ti-based composites using twodifferent powder metallurgy processes: Densification using severe plastic deformation viaEqual Channel Angular Pressing (ECAP) and Hydrogenation/Dehydrogenation (HDH)sintering processes (pressureless sintering and hot pressing).ECAP is a fast process basedon a severe plastic deformation of material at relatively low temperature. HDH processes usethe dehydrogenation of Ti as a leverage of the sintering. The different nanosizedreinforcements used in this study are the TiC spherical particles and the whisker shaped TiB.This study shows the influence of either the reinforcement nature and type, and the powdermetallurgy processes used, on the final microstructure and properties of the dense materials
10
Tan, Evren. "Severe Plastic Deformation Of Age Hardenable Aluminum Alloys." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614968/index.pdf.
Full textAbstract:
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.
11
Santos, Reinan Tiago Fernandes dos. "Estudo da deformação de nióbio empregando a técnica de prensagem em canais equiangulares (ECAP)." Pós-Graduação em Ciência e Engenharia de Materiais, 2018. http://ri.ufs.br/jspui/handle/riufs/7655.
Full textAbstract:
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES<br>This investigated the use of equiangular channel press (ECAP) in samples of pure niobium at room temperature up to 14 passes, using the Bc route, with a matrix with intersection angle between the channels of θ = 90º and 120º, with and curvature angle Ψ = 0°. During ECAP (equal channel angular pressing) deformation a bar is pressed through a rigid matrix consisting of two channels of the same cross-section, which intersect at an angle θ. The microstructure of the deformed samples has been analyzed with the aid of optic microscopy, scanning electron microscopy and Vickers Hardness (HV). With the deformation of pure niobium through ECAP, it was possible to refine the structure and increase the hardness due to the increase of the number of passes and the type of matrix. The results indicated that deformation of the niobium with a pass in the matrices of 90 ° and 120 ° was enough to produce the refinement of the microstructure and practically double the hardness values in relation to the material without deformation. The maximum microstructural refinement, steady state, occurred with 8 passes in the 120 ° matrix and 6 passes in the 90 ° matrix, indicating a higher deformation severity of the last matrix. The microstructures analyzed by scanning electron and optical microscopes revealed the microstructural changes with the increase of the number of passes and the type of matrix.<br>Este trabalho investigou o uso da prensagem em canais equiangulares (ECAP) em amostras de nióbio puro na temperatura ambiente até 14 passes, utilizando a rota Bc, com matrizes contendo ângulo de intersecção entre os canais de θ = 90º e 120°. Durante a deformação ECAP uma barra é pressionada através de uma matriz rígida consistindo de dois canais de mesma seção transversal, os quais se interceptam a um ângulo θ. A microestrutura das amostras deformadas foi analisada com auxílio de microscopia óptica, microscopia eletrônica de varredura e dureza Vickers (HV). Com a deformação do nióbio puro através do ECAP foi possível refinar a estrutura e aumentar a dureza em função do aumento do número de passes e do tipo de matriz. Os resultados indicaram que deformação do nióbio com um passe, nas matrizes de 90º e 120°, foi suficiente para produzir o refinamento da microestrutura e praticamente dobrar os valores de dureza em relação ao material sem deformação. O refinamento microestrutural máximo, estado estacionário, ocorreu com 8 passes na matriz de 120° e 6 passes na matriz de 90°, indicando maior severidade de deformação da última matriz. As microestruturas analisadas por microscopias ótica e eletrônica de varredura revelaram as mudanças microestruturais com o aumento do número de passes e com o tipo de matriz.<br>São Cristóvão, SE
12
Silva, Késia Filadélfia Dionizio. "Efeito do processo ECAP sobre a microestrutura e as propriedades mecânicas da liga Ti-35Nb-0,15Si e do Ti CP." Pós-Graduação em Ciência e Engenharia de Materiais, 2017. http://ri.ufs.br/jspui/handle/riufs/7204.
Full textAbstract:
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES<br>This work investigated the effect of different types of homogenization on the microstructure and the cold deformation behavior of Ti-35Nb-0,15Si alloy. Homogenization was performed under two conditions. Condition 1: treatment in ambient air at 1000 °C for 8, 24, 48, 72, 96 and 120 hours. Condition 2: treatment in argon atmosphere at 1000 °C for 8 hours. For the cold deformation study samples of the Ti-35Nb-0,15Si alloy and samples of Ti CP were deformed by ECAP with up to 8 passes, using the routes A and BC in a matrix with angle of intersection between the channels of Φ = 120º. The microstructural characterization was performed in the internal and external regions with the aid of optical microscopy, scanning electron microscopy and X-ray diffractograms. Vickers microhardness measurements were performed to evaluate the changes caused by deformation. In the ambient air atmosphere the samples showed the presence of the oxide layer influencing the hardness and the level of cold deformation. With the deformation of Ti-35Nb-0,15Si by ECAP it was possible to refine the structure and increase the hardness with increasing the number of passes. XRD analysis showed the presence of the α” phase induced by deformation. With the Ti CP deformed by ECAP, it was possible to analyze the microstructural evolution throughout the sample.<br>Este trabalho investigou o efeito de diferentes tipos de homogeneização sobre a microestrutura e o comportamento em deformação a frio da liga Ti-35Nb-0,15Si. A homogeneização foi realizada em duas condições. Condição 1: tratamento em atmosfera de ar ambiente na temperatura 1000 °C por 8, 24, 48, 72, 96 e 120 horas. Condição 2: tratamento em atmosfera inerte de argônio de 1000 °C por 8 horas. Para o estudo de deformação a frio, amostras da liga Ti-35Nb-0,15Si e amostras de Ti CP foram deformadas via ECAP com até 8 passes, utilizando as rotas A e BC numa matriz com ângulo de intersecção entre os canais de Φ = 120º. A caracterização microestrutural foi realizada nas regiões internas e externas com o auxílio de microscopia óptica, microscopia eletrônica de varredura e difratogramas de raios-X. Medidas de microdureza Vickers foram realizadas para avaliar as mudanças ocasionadas pela deformação. Em atmosfera de ar ambiente as amostras apresentaram a presença da camada de óxido influenciando na dureza e no nível de deformação a frio. Com a deformação de Ti-35Nb-0,15Si por ECAP foi possível refinar a estrutura e aumentar a dureza com o aumento do número de passes. A análise de DRX mostrou a presença da fase α’’ induzida por deformação. Com o Ti CP deformado por ECAP foi possível analisar a evolução microestrutural ao longo da amostra.<br>São Cristóvão, SE
13
Guerra, Maria Claudia Lopes. "Caracterização elétrica e mecânica da liga de alumínio AA 1050, com estrutura ultrafina processada pela técnica de deformação plástica intensa (DPI)." Universidade Presbiteriana Mackenzie, 2015. http://tede.mackenzie.br/jspui/handle/tede/1358.
Full textAbstract:
Made available in DSpace on 2016-03-15T19:36:54Z (GMT). No. of bitstreams: 1
Maria Claudia Lopes Guerra.pdf: 9968717 bytes, checksum: 7d0e4986884ffa382a835b641ed76573 (MD5)
Previous issue date: 2015-06-12<br>Fundo Mackenzie de Pesquisa<br>The ECAP (Equal Channel Angular Pressing) is a mechanical process of Severe Plastic Deformation (SPD) where a sample is subjected to a shearing force when passing through the region of intersection of two channels. The main goal of this method is Severe Plastic Deformation achieve a microstructure with ultrafine grains, which have much higher than the equivalent coarse grain materials physical properties, such as an increase in strength and toughness simultaneously. What makes this increasingly interesting technique is that as there is no reduction cross section is possible to obtain plastic strain accumulation and therefore gain in grain order of nanometer scale. The great advantage of ECAP is to achieve a much higher degree of strain hardening than obtained by conventional methods of plastic deformation, and consequently a grain refining much higher as well. The importance of the study of severe plastic deformation process is on improving the mechanical performance of the materials and the possibility of a better understanding of the mechanisms of strain hardening, which may indicate a new path for producing high-strength materials, possibly scaled industrial. In this work are presented the microstructural, mechanical and electrical analysis of the aluminum alloy AA 1050 samples, commonly used for electrical purposes, with ultrafine grains (typical grain size below a micron) resulting from processing by ECAP, based on the method of SPD.<br>A PCE (Prensagem em Canais Equiangulares) consiste num processo mecânico de Deformação Plástica Intensa (DPI) onde um corpo de prova é sujeito a um esforço de cisalhamento ao passar pela região de intersecção de dois canais. Os principais objetivos desse método de Deformação Plástica Intensa é alcançar uma microestrutura com grãos ultrafinos, os quais possuem propriedades físicas muito superiores aos equivalentes materiais de grãos grosseiros, como um aumento em resistência mecânica e tenacidade simultâneas. O que torna esta técnica cada vez mais interessante é que como não há redução da seção transversal é possível obter acumulo de deformação plástica e com isso obter grãos na ordem de escala nanométrica. A grande vantagem do PCE é alcançar um grau de encruamento muito superior do que obtido por métodos convencionais de deformação plástica, e consequentemente, um refino de grão muito superior também. A importância do estudo do processo de deformação plástica intensa está na melhoria do desempenho mecânico dos materiais e na possibilidade de uma melhor compreensão dos mecanismos de encruamento, fato que pode indicar um novo caminho para a produção de materiais de alta resistência mecânica, possivelmente em escala industrial. Nesse trabalho são apresentadas as análises microestruturais, mecânicas e elétricas de amostras de ligas de alumínio AA 1050, comumente utilizadas para fins elétricos, com estrutura de grãos ultrafinos (tamanho de grão típico abaixo de um micrometro) resultantes do processamento por PCE, baseada no método de DPI.
14
Hockauf, Kristin. "Ermüdungs- und Rissfortschrittsverhalten ausscheidungshärtbarer ultrafeinkörniger Aluminiumlegierungen." Doctoral thesis, Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-76030.
Full textAbstract:
Ultrafeinkörnige metallische Werkstoffe haben verstärkt wissenschaftliche Bedeutung erlangt. Um dieser neuartigen Werkstoffklasse über die grundlagenorientierte Forschung hinaus einen Einsatz in technischen Anwendungen zu ermöglichen, ist es notwendig, deren Verhalten unter verschiedenen einsatzrelevanten Belastungsbedingungen vorhersagen zu können. In der vorliegenden Arbeit wird das Schädigungsverhalten einer ultrafeinkörnigen Aluminiumlegierung in den Bereichen der hochzyklischen (HCF) und niedrigzyklischen (LCF) Ermüdung sowie des Rissfortschritts untersucht. Im Mittelpunkt steht dabei die Identifikation der mikrostrukturell wirksamen Mechanismen bei der Entstehung und Ausbreitung von Ermüdungsrissen. Es werden ein homogen ultrafeinkörniger und ein bimodaler Zustand sowie verschiedene duktilitätsoptimierte Zustände betrachtet und systematisch der Einfluss der Korngröße, der Korngrößenverteilung, der Ausscheidungscharakteristik sowie der Festigkeit und Duktilität auf das Ermüdungs- und Rissfortschrittsverhalten ermittelt. Die Untersuchungen zeigen, dass das Schädigungsverhalten der ultrafeinkörnigen Aluminiumlegierung insbesondere durch die Korngröße und Korngrößenverteilung sowie den Kohärenzgrad der festigkeitssteigernden Ausscheidungen beeinflusst wird.
15
Olmez, Rabia. "Combinatorial Study Of Hydrogen Storage Alloys." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610552/index.pdf.
Full textAbstract:
A combinatorial study was carried out for hydrogen storage alloys which involve processes similar to those normally used in their fabrication. The study utilized a single sample of combined elemental (or compound) powders which were milled and consolidated into a bulk form and subsequently deformed to heavy strains. Material library was obtained in a post annealing treatment carried out at elevated temperatures which brings about solid state reactions between the powders yielding equilibrium phases in the respective alloy system. A sample comprising the material library was then pulverized and screened for hydrogen storage composition. X-ray diffraction was used as a screening tool, the sample having been examined both in as-processed and hydrogenated state. The method was successfully applied to Mg-Ni, and Mg-Ni-Ti yielding the well known Mg2Ni as the storage composition. It is concluded that partitioning of the alloy system into regions of similar solidus temperature would be required to enrich the material library.
16
Foley, David Christopher. "Ferritic-martensitic steel subjected to equal channel angular extrusion." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2537.
Full text
17
Harrison, Nicholas. "Equal channel angular pressing of elemental & alloyed P/M aluminium systems." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5063/.
Full textAbstract:
Aluminium powder metallurgy provides lightweight automobile components for reduced energy consumption. Conventional press-and-sinter methods can leave porosity in final parts, which reduces strength of the alloy. Equal Channel Angular Pressing (ECAP) can be used to increase density of powder compacts after sintering via severe plastic deformation. Solid state sintering of pure aluminium and liquid phase sintering of a commercial Al-Sn bearing alloy were analysed with industrial collaborative support. The use of room temperature ECAP to these sintered materials was investigated. Cold compaction produced a porous region on the outside of all samples due to increased friction at the die wall. The application of ECAP to pure aluminium and bearing alloys caused elongation in the longitudinal section and a relatively equiaxed microstructure in the transverse section. Sintering at 500°C for 1 and lOhours and 550°C for lh was ineffective as liquid tin did not wet the aluminium effectively. After ECAP, density and hardness increased with refined grain sizes and formed two distinct regions; a denser, deformed core and a non-deformed skin, which resulted from non-uniform densification after cold compaction.
18
Shi, Qi (Alex). "Recycling of titanium alloys from machining chips using equal channel angular pressing." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/19515.
Full textAbstract:
During the traditional manufacturing route, there are large amount of titanium alloys wasted in the form of machining chips. The conventional recycling methods require high energy consumption and capital cost. Equal channel angular pressing (ECAP), one of the severe plastic deformation techniques, has been developed to recycle the metallic machining chips. The purpose of the PhD work is to realize the ECAP recycling of titanium alloys, in particular Ti-6Al-4V and Ti-15V-3Cr-3Al-3Sn, and investigate the effects of processing parameters on the resultant relative density, microstructure evolution, texture development and microhardness homogeneity. The microstructures of Ti-6Al-4V and Ti-15V-3Cr-3Al-3Sn machining chips obtained from conventional turning (CT) and ultrasonically assisted turning (UAT) were initially investigated. It was found that ultrafine grains were formed in the primary and secondary shear zones. For Ti-6Al-4V chips, the β phase in the shear zones was refined into nano-sized equiaxed grains and aligned up to form banded structures. For Ti-15V-3Cr-3Al-3Sn chips, the nano-crystalline grains were enveloped in the shear zones and have clear boundaries to the surrounding matrix. It was observed that in terms of microstructure, there is no significant difference between CT and UAT chips. Recycling of Ti-6Al-4V machining chips was carried out at moderate temperatures with various back-pressures. For single-pass samples, the relative density was increased with the applied back-pressure and operating temperature. It was found that after multiple passes, near fully dense recycled Ti-6Al-4V can be fabricated. The microstructure observations showed that the nano-sized equiaxed and elongated grains co-existed with relatively coarser lamellar structures which were initially refined after the first pass. In the subsequent passes, the fraction of equiaxed nano-grains increased with the number of passes. The original β phase banded structures were fragmented into individual nano-sized grains randomly distributed within α matrix. The chip boundaries were eliminated and nano-crystalline microstructure region was observed at the chip/chip interface after multiple passes. In the sample processed at 550 °C, < a →+c → > type dislocations were observed and oxide layer at chip/chip interface was detected. The texture evolution was investigated using electron backscatter diffraction. It was found that the recycled samples performed a strong basal texture along the normal to ECAP inclination direction after the first pass. After multiple passes, in addition to the normal to inclination direction, the recycled Ti-6Al-4V exhibits a basal texture towards the transverse direction. Microhardness mapping showed that the average hardness and degree of homogeneity were increased with number of passes, while the imposed back-pressure had little effect on the average value and homogeneity. Recycling of Ti-15V-3Cr-3Al-3Sn machining chips was implemented using similar ECAP conditions. The effects of processing parameters, such as back-pressure, operating temperature and number of passes, on the relative density were similar to those for Ti-6Al-4V. Microstructural characterization showed that equiaxed instead of needle shaped α precipitates formed in the β matrix due to the high dislocation density and sub-grain boundaries introduced during ECAP. In terms of microhardness, the maximum hardness was obtained at the specimen pressed at 450 °C. It was found that the applied back-pressure and number of passes enabled to improve the homogeneity, but had little effect on the average hardness.
19
Haase, Matthias [Verfasser]. "Mechanical Properties Improvement in Chip Extrusion with Integrated Equal Channel Angular Pressing / Matthias Haase." Aachen : Shaker, 2014. http://d-nb.info/1049379497/34.
Full text
20
Vuong, Linda. "Microstructure and texture development in AZ31 magnesium alloy processed by equal channel angular pressing." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99547.
Full textAbstract:
Enhancement of the ductility is very important for the successful commercialization of magnesium alloys. Among other methods, this can be achieved by refining the grain structure through equal channel angular pressing (ECAP) or extrusion. Preliminary work was conducted using as-cast AZ-31, but this was found to be of low ductility and extruded bars were used for the rest of the experimentation. These were annealed at 350°C for 1 hour and extrusion was carried out at three temperatures, 200, 250 and 300°C, using routes A, BC and C at a speed of 5 mm/s for up to 8 passes. It is apparent that increasing the operating temperature increases the final grain size as a result of grain growth. Conversely increasing the number of passes results in a finer grain size because of the accumulation of shear. However, grain growth can affect the final grain size for all three routes. After one ECAP pass, a preferred orientation with the basal planes inclined at 45° to the ECAP axis is observed. For route A, as more and more passes are employed, the original fiber texture tends towards a rolling texture. By contrast, for route C, repeating the ECAP steps does not change the texture, which retains the 45° preferential orientation. The mechanical properties indicate that using a path with shearing in more directions, such as route C, results in increased ductility, with a wider flow curve than for route A. As the temperature of ECAPping is increased, the strength of the extruded product increases and the ductility decreases. This appears to be due to the coarser grain size of the 300°C product and indicates that the effect of grain refinement is greater than that of texture.
21
Gan, Weimin. "Texture and microstructure development of the silicon containing magnesium alloys after equal channel angular pressing." Clausthal [Univ.-Bibliothek], 2008. http://d-nb.info/990980464/34.
Full text
22
Terhune, Shannon Derek. "An electron backscatter diffraction analysis of the microstructure of pure aluminum processed by equal-channel angular pressing." Thesis, Monterey, California. Naval Postgraduate School, 1998. http://hdl.handle.net/10945/8304.
Full textAbstract:
Equal-channel angular (ECA) pressing is a promising method to achieve refinement of grain size to 1.0 micrometer or less for aluminum and its alloys. Computer-aided electron backscatter diffraction (EBSD) analysis of high purity aluminum (99.99%) which had been subjected to one pass, four passes, and twelve passes through an ECA die was performed. Grain and subgrain size and boundary misorientation distributions during such large-strain deformation processing were of particular interest. A texture was present after one pressing and the boundary misorientation distribution had a peak at 5 deg - 10 deg although boundaries were present in all misorientation ranges. Fine equaixed grains were achieved after twelve passes through the ECA die, accompanied by random orientation and misorientation distributions
23
Morehead, Mason Dale. "Machinability and microstructure stability during the machining of pure copper and titanium processed by equal channel angular pressing." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1181251992/.
Full text
24
Gan, Weimin [Verfasser]. "Texture and microstructure development of the silicon containing magnesium alloys after equal channel angular pressing / vorgelegt von Weimin Gan." Clausthal : [Univ.-Bibliothek], 2008. http://d-nb.info/990980464/34.
Full text
25
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.
Full textAbstract:
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
26
Rodrigues, Ana Carolina Oliveira da Palma [UNESP]. "Efeito no processo ECAP (EQUAL CHANNEL ANGULAR) na microestrutura e nas propriedades mecânicas de uma liga comercial de alumínio AA3104." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/94461.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:27:12Z (GMT). No. of bitstreams: 0
Previous issue date: 2013-03-01Bitstream added on 2014-06-13T18:31:01Z : No. of bitstreams: 1
rodrigues_acop_me_guara.pdf: 1644322 bytes, checksum: f877159b9b74dfe3d7b6d20589e59c87 (MD5)<br>A Engenharia tem buscado a fabricação de materiais com elevados valores de resistência mecânica e tenacidade. Uma das formas de obter tais propriedades é promover a redução do tamanho de grão do material. A fim de reduzir o tamanho de grãos e obter tais propriedades neste trabalho foi aplicado o processo ECAP (Equal Channel Angular Pressing) em amostras da Liga de Alumínio AA3104, liga de Al-Mn não Tratável Termicamente. As amostras de alumínio foram deformadas plasticamente por cisalhamento simples na região de interseção dos canais. A repetição deste processo resulta no encruamento do material. Os resultados mostram que após o processamento a microestrutura esta com grãos alongados devido ao encruamento do material e por meio de ensaios de dureza Vickers verifica-se um aumento de dureza após 3 passes de ECAP aplicados<br>A constant search in Engineering is the manufacturing of materials with high values of strength and tenacity. One way to obtain such properties is to promote the reduction of grain size of the material. In order to reduce the size of grains and obtain such properties in this work was applied the ECAP (Equal Channel Angular Pressing) process in samples of Aluminum Alloy AA3104, Al-Mn alloy is non-heat treatable. A sample of aluminum was deformed by simple shear in the intersection of the channels that leads to a severe plastic deformation. The repetition of the process results in a material with a cold work hardening. The results show that after the processing ECAP microstructure with elongated grains and by Vickers hardness testing the hardness increase after the three pass of ECAP applied
27
Rodrigues, Ana Carolina Oliveira da Palma. "Efeito no processo ECAP (EQUAL CHANNEL ANGULAR) na microestrutura e nas propriedades mecânicas de uma liga comercial de alumínio AA3104 /." Guaratinguetá, 2013. http://hdl.handle.net/11449/94461.
Full textAbstract:
Orientador: Angelo Caporalli Filho<br>Banca: Valdir Alves Guimarães<br>Banca: Wyser José Yamakami<br>Resumo: A Engenharia tem buscado a fabricação de materiais com elevados valores de resistência mecânica e tenacidade. Uma das formas de obter tais propriedades é promover a redução do tamanho de grão do material. A fim de reduzir o tamanho de grãos e obter tais propriedades neste trabalho foi aplicado o processo ECAP (Equal Channel Angular Pressing) em amostras da Liga de Alumínio AA3104, liga de Al-Mn não Tratável Termicamente. As amostras de alumínio foram deformadas plasticamente por cisalhamento simples na região de interseção dos canais. A repetição deste processo resulta no encruamento do material. Os resultados mostram que após o processamento a microestrutura esta com grãos alongados devido ao encruamento do material e por meio de ensaios de dureza Vickers verifica-se um aumento de dureza após 3 passes de ECAP aplicados<br>Abstract: A constant search in Engineering is the manufacturing of materials with high values of strength and tenacity. One way to obtain such properties is to promote the reduction of grain size of the material. In order to reduce the size of grains and obtain such properties in this work was applied the ECAP (Equal Channel Angular Pressing) process in samples of Aluminum Alloy AA3104, Al-Mn alloy is non-heat treatable. A sample of aluminum was deformed by simple shear in the intersection of the channels that leads to a severe plastic deformation. The repetition of the process results in a material with a cold work hardening. The results show that after the processing ECAP microstructure with elongated grains and by Vickers hardness testing the hardness increase after the three pass of ECAP applied<br>Mestre
28
Pontes, Marcos Javert Hilgemberg. "Estudo do processamento de um aço inoxidável dúplex SAF2205 por canal angular." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2012. http://tede2.uepg.br/jspui/handle/prefix/1446.
Full textAbstract:
Made available in DSpace on 2017-07-21T20:42:44Z (GMT). No. of bitstreams: 1
Marcos Pontes.pdf: 4006153 bytes, checksum: 42b95748e61f5bc3de1b41ca1fbd649b (MD5)
Previous issue date: 2012-02-29<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>The processing by equal channel angular extrusion of a duplex stainless steel UNS32205/S31803, with ferritic-austenitic structures, was studied, processing until four passes each sample. The reason of this processing was to promote a grain
refinement in the material, to achieve ultrafined grain material by severe plastic deformation. Different number of passes were used in this processing to evaluate how the number of extrusions in the same sample influences the deformation
imposed to the material. After processing, some different heat treatments were done in the samples to evaluate the recrystallization process in the processed material. In this study, it was possible to verify the increasing level of deformation in the material after every new processing in the sample, this was verified by the changes in grain orientation and by microstructure evaluation. It was possible to reduce the stress
level to values that can avoid the breaking of punctures during processing, this allowed to process the material with a greater number of passes in a material with a high resistance like the duplex stainless steels. Strain bands were found in the structure of the processed material, this indicates high levels of deformation.<br>Foi realizado o estudo do processamento de um aço inoxidável dúplex SAF2205,com microestrutura ferrítica-austenítica, por extrusão em canal angular por até quatro passes. O objetivo deste processamento foi a obtenção de um refino de grãos no material, atingindo uma estrutura de grãos ultrafinos, a partir da aplicação de deformações plásticas severas. Foram realizados diferentes modos de processamento, variando o número de passes pela matriz e depois foi avaliado como este parâmetro influencia na deformação imposta ao material. Após o processamento por ECA (Extrusão por Canal Angular), foram realizados diferentes tratamentos térmicos para avaliar a cinética de recristalização do material. Foi possível verificar o nível crescente de deformação do material após cada passe, com o acompanhamento da orientação dos grãos e avaliações microestruturais. Foi possível reduzir os níveis de tensões o suficiente para evitar a quebra de punções
durante o processamento, permitindo um número maior de passes para um material com a resistência do aço inoxidável dúplex. Foram verificadas bandas de deformação no material processado, indicando níveis elevados de deformação.
29
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.
Full textAbstract:
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.
30
恵子, 名取, та Keiko Natori. "微細複合組織金属の変形機構および塑性加工性に関する研究". Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12867122/?lang=0, 2014. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12867122/?lang=0.
Full textAbstract:
ヘテロ構造組織を有する鉄・非鉄金属の組織形態に注目して,微視的構造やその挙動が巨視的現象(変形特性,成形性)として発現するメカニズムを解明することを目的とした.鉄系金属ではDual Phase型高張力鋼のスプリングバック現象のひずみ速度依存性,非鉄系金属では半凝固鋳造法と強ひずみ加工を組み合わせた亜共晶アルミニウム合金の衝撃後方押出し成形性に注目した.これらの検討によりいずれの試料においても,結晶粒界よりもスケールの大きいヘテロ構造に由来した変形機構が支配的であることが明らかになった.<br>博士(工学)<br>Doctor of Philosophy in Engineering<br>同志社大学<br>Doshisha University
31
Štěpánek, Roman. "Studium substrukturních změn ultrajemnozrnných Mg-slitin při cyklickém zatěžování a teplotní expozici." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-263403.
Full textAbstract:
This thesis deals with complex analysis of fine-grained magnesium alloy AZ91 prepared by ECAP process. Mechanical properties of investigated alloy in different states at various external conditions are compared. The structure of this material is inherently unstable therefore changes on microstructural and sub-microstructural level occur during thermal exposure and/or mechanical loading. These changes are analysed and quantified for investigated alloy in selected states in this thesis.
32
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
33
Gonzalez, Jeremy. "Mechanical Properties of Bulk Nanocrystalline Austenitic Stainless Steels Produced by Equal Channel Angular Pressing." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-08-10087.
Full textAbstract:
Bulk nanocrystalline 304L and 316L austenitic stainless steels (SS) were produced by equal channel angular pressing(ECAP) at elevated temperature. The average grain size achieved in 316L and 304 L SS is ~ 100 nm, and grain refinement occurs more rapid in 316 L SS than that in 304L. Also the structures are shown to retain a predominant austenite phase. Hardness increases by a factor of about 2.5 in both steels due largely to grain refinement and an introduction of a high density of dislocations. Tensile strength of nanocrystalline steels exceeds 1 GPa with good ductility in both systems. Mechanical properties of ECAPed 316L are also shown to have less dependence on strain rate than ECAPed 304L. ECAPed steels were shown to exhibit thermal stability up to 600oC as indicated by retention of high hardness in annealed specimens. Furthermore, there is an increased tolerance to radiation-induced hardening in the nanocrystalline equiaxed materials subjected to 100 keV He ions at an average dose of 3-4 displacement-per-atom level at room temperature. The large volume fraction of high angle grain boundaries may be vital for enhanced radiation tolerance. These nanocrystalline SSs show promise for further research in radiation resistant structural materials for next-generation nuclear reactor systems.
34
Chou, Tun-Yu, and 周暾煜. "Effect of equal channel angular pressing (ECAP) and additives on hydrogen storage properties of AZ alloy." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/95744362197005145252.
Full textAbstract:
碩士<br>國立臺灣科技大學<br>機械工程系<br>104<br>In this study, the cast AZ31 and AZ61 magnesium alloys were processed by equal channel angular pressing (ECAP) and were comminuted into chips by filing with a rasp to measure the properties of hydrogen storage. Effects of processing pass and route of ECAP on AZ series magnesium alloys hydrogen storage properties were investigated. In addition to studying the effects of ECAP on hydrogen storage properties, we also investigated the effects of additives on hydrogen storage properties by adding activated carbon (AC) and nickel powder (Nip). Different from high energy ball milling technique, the catalysts were added and mixed by gravity cast with mechanical stirring to prepare Mg-based composite materials for hydrogen storage. The materials were further comminuted into chips by filing with a rasp to measure the hydrogen storage properties of AZ metal matrix composites (MMCs). The absorption and desorption of hydrogen were measured by Sievert-type hydrogen measurement system in this research.
These results indicated that after the ECAP processing, the AZ alloys lead to severe dynamic recrystallization and achieved grain refinement. AZ31 processed by ECAP route BC with 8 passes provided the best result of the grain refinement, and elevated the absorption and desorption rate of hydrogen, exhibited high gravimetric hydrogen storage capacity of 7 wt.%. Furthermore, compared to the AZ alloys without any additives, AZ31-5C and AZ31-5C-0.5Ni significantly increased the absorption and desorption rate of hydrogen and the hydrogen storage capacity were 6.9 wt.% and 6.3 wt.%, respectively.
35
Srba, Ondřej. "Komplexní studium jemnozrnných polykrystalů Cu a slitiny CuZr připravených metodami equal channel angular pressing a high pressure torsion." Doctoral thesis, 2012. http://www.nusl.cz/ntk/nusl-311803.
Full textAbstract:
Title: Complex investigation of fine-grained polycrystals of Cu and CuZr alloy processed by equal channel angular pressing and high pressure torsion Author: RNDr.Ondřej Srba Department: Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University Prague Supervisor: Doc. RNDr. Miloš Janeček, CSc. Abstract: In the thesis the microstructure development, mechanical, elastic and corrosion properties of deformed specimens of pure Cu and binary alloy CuZr processed by equal channel angular pressing (ECAP) are investigated. Several properties of pure Cu processed by ECAP are compared with properties of the same material processed by high pressure torsion (HPT). The microstructure development is characterized in detail by several experimental techniques (light and electron microscopy, electron back scatter diffraction, positron annihilation spectroscopy, etc.). The microstructure development in specimens processed by ECAP is characterized by the continuous fragmentation of the initial coarse grain structure and the formation of new grains having the sizes in the submicrocrystalline range (of 460 nm and 260 nm in Cu and CuZr alloy, respectively). During the deformation by ECAP the fraction of high-angle grain boundaries, the dislocation density and the concentration of vacancies are...
36
Chen, Yong-Lin, and 陳永霖. "Effect of Different Carbon Additives on Hydrogen Storage Properties of AZ31 Magnesium Alloy by High Energy Ball Milling (HEBM) or Equal Channel Angular Pressing (ECAP)." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/amn6e3.
Full textAbstract:
碩士<br>國立臺灣科技大學<br>機械工程系<br>106<br>This study investigates the effect of additives on the hydrogen storage properties of AZ31 magnesium alloys. Activated carbon (AC), carbon black (CB), graphene (G) were used as catalysts in different weight percentages (0wt.%, 1wt.%, 3wt.%). Discuss the effect of different carbon additives and their content on the hydrogen storage performance. In addition, this study also explored the effect of different processes on hydrogen storage performance. Use the same process time as a benchmark for comparison. Firstly, the AZ31 magnesium matrix composites with different carbon additives were prepared by casting, and then processed by high energy ball milling (HEBM) or equal channel angular pressing (ECAP). Finally, the measurement of hydrogen absorption and desorption is performed.
The results show that after the HEBM process, adding carbon material can effectively improve the hydrogen storage performance of AZ31 magnesium alloys. The increase in hydrogen storage performance from large to small additions of graphene, carbon black and activated carbon. After the ECAP process, only added activated carbon or carbon black can effectively improve the hydrogen storage performance of AZ31 magnesium alloys. The addition of graphene will result in a decrease in hydrogen storage performance. The increase in hydrogen storage performance from large to small addition of carbon black and activated carbon. Compared with the HEBM or ECAP process, the AZ31 magnesium alloy without added carbon has better hydrogen storage performance through the ECAP process, while the AZ31 magnesium matrix composite with carbon added has better hydrogen storage performance through the HEBM process.
37
Sabat, Rama Krushna. "Evolution of Microstructure and Texture during Severe Plastic Deformation of a Magnesium-Cerium Alloy." Thesis, 2014. http://etd.iisc.ac.in/handle/2005/2956.
Full textAbstract:
Magnesium alloys have poor formability at room temperature, due to a limited number of slip systems owing to the hexagonal closed packed structure of magnesium. One possibility to increase the formability of magnesium alloys is to refine the grain size. A fine grain magnesium alloy shows high strength and high ductility at room temperature, hence an improved formability. In addition to grain refinement, the formability of Mg alloys can be improved by controlling crystallographic texture. Severe plastic deformation (SPD) processes namely, equal channel angular pressing (ECAP) and multi-axial forging (MAF) have led to improvement in room temperature mechanical property of magnesium alloys. Further, it has been reported that by adding rare earth elements, room temperature ductility is enhanced to nearly 30%. The increase in property is attributed to crystallographic texture. Many rare earth elements have been added to magnesium alloys and new alloy systems have been developed. Amongst these elements, Ce addition has been shown to enhance the tensile ductility in rolled sheets at room temperature by causing homogeneous deformation. It has been observed that processing of rare-earth containing alloys below 300°C is difficult. Processing at higher temperatures leads to grain growth which ultimately leads to low strength at room temperature. The present thesis is an attempt to combine the effect SPD and rare earth addition, and to examine the overall effect on microstructure and texture, hence on room temperature mechanical properties. In this thesis, Mg-0.2%Ce alloy has been studied with regard to the two SPD processes, namely, ECAP and MAF. The thesis has been divided into six chapters. Chapter 1 is dedicated to introduction and literature review pertaining to different severe plastic deformation processes as applied to different Mg alloys. Chapter 2 includes the details of experimental techniques and characterization procedures, which are commonly employed for the entire work.
Chapter 3 addresses the effect of ECAP on the evolution of texture and microstructure in Mg-0.2%Ce alloy. ECAP has been carried out on two different initial microstructure and texture in the starting condition, namely forged and extruded. ECAP has been successfully carried out for the forged billets at 250°C while cracks get developed in the extruded billet when ECAP was done at 250°C. The difference in the deformation behaviour of the two alloys has been explained on the basis of the crystallographic texture of the initial materials. The microstructure of the ECAP materials indicates the occurrence of recrystallization. The recrystallization mechanism is identified as “continuous dynamic recovery and recrystallization” (CDRR) and is characterized by a rotation of the deformed grains by ~30⁰ along c-axis. The yield strengths and ductility of the two ECAP materials have been found quite close. However, there is a difference in the yield strength as well as ductility values when the materials were tested under compression. The extruded billet has the tension compression asymmetry ~1.7 while the forged material has the asymmetry as ~2.2. After ECAP, the yield asymmetry reduces to ~1 for initially extruded billet, while for the initially forged billet the yield asymmetry value reduces to ~1.9.
In chapter 4, the evolution of microstructure and texture was examined using another severe plastic deformation technique, namely multi axial forging (MAF). In this process, the material was plastically deformed by plane strain compression subsequently along all three axes. In this case also two different initial microstructures and texture were studied, namely the material in as cast condition and the extruded material. The choice of initial materials in this case was done in order to examine the effect of different initial grain size in addition to different textures. By this method, the alloy Mg-0.2%Ce could be deformed without fracture at a minimum temperature of 350⁰C leading to fine grain size (~3.5 µm) and a weak texture. Grain
refinement was more in the initial cast billets compared to the initial extruded billet after processing. The mechanism of grain refinement has been identified as twin assisted dynamic recrystallization (TDRX) and CDRR type. The mechanical properties under tension as well as under compression were also evaluated in the present case. The initially extruded billet has shown low tension compression asymmetry (~1.2) than cast billet (~1.9), after MAF. Chapter 5 addresses the exclusive effect of texture on room temperature tensile properties of the alloy. Different textures were the outcomes of ECAP and MAF processes. In this case, in order to obtain an exact role of texture, a third of deformation mode, rolling, was also introduced. All the processed materials were annealed to obtain similar grain size but different texture. A similar strength and ductility for ECAP and MAF, where the textures were qualitatively very different, was attributed to the fact that texture of both the ECAP and MAF processed materials, was away from the ideal end orientation for tensile tests. In chapter 7, the final outcomes of the thesis have been summarized and scope for the future work has been presented.
38
Sabat, Rama Krushna. "Evolution of Microstructure and Texture during Severe Plastic Deformation of a Magnesium-Cerium Alloy." Thesis, 2014. http://etd.iisc.ernet.in/handle/2005/2956.
Full textAbstract:
Magnesium alloys have poor formability at room temperature, due to a limited number of slip systems owing to the hexagonal closed packed structure of magnesium. One possibility to increase the formability of magnesium alloys is to refine the grain size. A fine grain magnesium alloy shows high strength and high ductility at room temperature, hence an improved formability. In addition to grain refinement, the formability of Mg alloys can be improved by controlling crystallographic texture. Severe plastic deformation (SPD) processes namely, equal channel angular pressing (ECAP) and multi-axial forging (MAF) have led to improvement in room temperature mechanical property of magnesium alloys. Further, it has been reported that by adding rare earth elements, room temperature ductility is enhanced to nearly 30%. The increase in property is attributed to crystallographic texture. Many rare earth elements have been added to magnesium alloys and new alloy systems have been developed. Amongst these elements, Ce addition has been shown to enhance the tensile ductility in rolled sheets at room temperature by causing homogeneous deformation. It has been observed that processing of rare-earth containing alloys below 300°C is difficult. Processing at higher temperatures leads to grain growth which ultimately leads to low strength at room temperature. The present thesis is an attempt to combine the effect SPD and rare earth addition, and to examine the overall effect on microstructure and texture, hence on room temperature mechanical properties. In this thesis, Mg-0.2%Ce alloy has been studied with regard to the two SPD processes, namely, ECAP and MAF. The thesis has been divided into six chapters. Chapter 1 is dedicated to introduction and literature review pertaining to different severe plastic deformation processes as applied to different Mg alloys. Chapter 2 includes the details of experimental techniques and characterization procedures, which are commonly employed for the entire work.
Chapter 3 addresses the effect of ECAP on the evolution of texture and microstructure in Mg-0.2%Ce alloy. ECAP has been carried out on two different initial microstructure and texture in the starting condition, namely forged and extruded. ECAP has been successfully carried out for the forged billets at 250°C while cracks get developed in the extruded billet when ECAP was done at 250°C. The difference in the deformation behaviour of the two alloys has been explained on the basis of the crystallographic texture of the initial materials. The microstructure of the ECAP materials indicates the occurrence of recrystallization. The recrystallization mechanism is identified as “continuous dynamic recovery and recrystallization” (CDRR) and is characterized by a rotation of the deformed grains by ~30⁰ along c-axis. The yield strengths and ductility of the two ECAP materials have been found quite close. However, there is a difference in the yield strength as well as ductility values when the materials were tested under compression. The extruded billet has the tension compression asymmetry ~1.7 while the forged material has the asymmetry as ~2.2. After ECAP, the yield asymmetry reduces to ~1 for initially extruded billet, while for the initially forged billet the yield asymmetry value reduces to ~1.9.
In chapter 4, the evolution of microstructure and texture was examined using another severe plastic deformation technique, namely multi axial forging (MAF). In this process, the material was plastically deformed by plane strain compression subsequently along all three axes. In this case also two different initial microstructures and texture were studied, namely the material in as cast condition and the extruded material. The choice of initial materials in this case was done in order to examine the effect of different initial grain size in addition to different textures. By this method, the alloy Mg-0.2%Ce could be deformed without fracture at a minimum temperature of 350⁰C leading to fine grain size (~3.5 µm) and a weak texture. Grain
refinement was more in the initial cast billets compared to the initial extruded billet after processing. The mechanism of grain refinement has been identified as twin assisted dynamic recrystallization (TDRX) and CDRR type. The mechanical properties under tension as well as under compression were also evaluated in the present case. The initially extruded billet has shown low tension compression asymmetry (~1.2) than cast billet (~1.9), after MAF. Chapter 5 addresses the exclusive effect of texture on room temperature tensile properties of the alloy. Different textures were the outcomes of ECAP and MAF processes. In this case, in order to obtain an exact role of texture, a third of deformation mode, rolling, was also introduced. All the processed materials were annealed to obtain similar grain size but different texture. A similar strength and ductility for ECAP and MAF, where the textures were qualitatively very different, was attributed to the fact that texture of both the ECAP and MAF processed materials, was away from the ideal end orientation for tensile tests. In chapter 7, the final outcomes of the thesis have been summarized and scope for the future work has been presented.
39
Stoica, Grigoreta Mihaela. "Equal-Channel-Angular Processing (ECAP) of Materials: Experiment and Theory." 2007. http://etd.utk.edu/2007/StoicaGrigoreta.pdf.
Full text
40
Chen, Jinyu. "Mechanical response and failure mechanism of 2024 aluminum alloy processed by equal channel angular pressing." 2004. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=95190&T=F.
Full text
41
Chen, Chong-Rui, and 陳崇瑞. "The effect of equal-channel angular pressing and Y addition on the mechanical properties of Mg-Li alloys." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/b6h8b8.
Full textAbstract:
碩士<br>國立東華大學<br>材料科學與工程學系<br>102<br>In order to improve the mechanical properties of Mg-Li alloys, the effect of equal channel angular press (ECAP) and minor amounts of Y addition in Mg-Li alloys were investigated. The results showed that the mechanical strengths of the as-cast Mg-9wt%Li-1wt%Zn (LZ91) could be increased obviously after 4 cycles of ECAP. It is inferred that the grain size refining by ECAP improved the mechanical properties of LZ91.
Regarding the Y addition in Mg-7wt%Li-1wt%Zn (LZ71) alloy, the mechanical strengths of as-extruded and cold worked Mg-7wt%Li-1wt%Zn-0.5wt%Y(LZW710) alloy increased, but the elongations decreased slightly. The EDS and XRD results showed that the second phase of Mg24Y5 constrained the grain growth of α and β phases, and the grain refining of the LZW710 alloy contributed to the higher strengths. Besides, the larger amounts of cold rolling reduction, the higher strengths of alloys. The highest ultimate strength (340MPa) of LZW710 alloy could be achieved after 40% cold rolling.
Finally, the alloys (0.5wt%Y added [LZW910], 1wt%Y added [LZW911]) with different amounts of Y addition in Mg-9wt%Li-1wt%Zn (LZ91) were investigated, too. The results showed that the strengths of alloys increased as the amounts of Y addition increasing. According to the microstructural analysis, α phase became globular and more uniformly distributed, and grain size of β matrix was refined as the Y addition increasing. Moreover, the amounts of fine second phase of Mg24Y5 phase identified by EDS was increased. It is inferred that the strengthening mechanisms of Y-bearing alloys are combination of dispersion and grain refining effects.
42
Lin, Chien-Cheng, and 林建成. "Effect of Equal Channel Angular Pressing on the Mechanical Properties of Magnesium Alloy Matrix Composites with X-Ray Defect Detection." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/c6852u.
Full textAbstract:
博士<br>國立臺灣科技大學<br>機械工程系<br>106<br>This study is devoted to investigating the influence of vacuum casting parameters on defects in magnesium alloy, and to exploring the changes in the mechanical properties and microstructural evolution under equal channel angular pressing(ECAP). The Taguchi method in conjunction with an X-ray image detector was employed to determine the percentage of internal defect area (PIDA). X-ray images of magnesium alloy specimens were filtered, binarized, and edge enhanced. The calculated area of internal defects was then used to optimize process parameters according to multiple performance indicators. Based on experimental results, the combination of temperature 720℃, vacuum 30 torr, for 2 hours, steel, and 120 min of argon gas injection and parameters (780℃, 30 torrs, 1 hours, steels, and 120 min of argon gas injection) were both deemed optimal. The uniformity in the percentage of internal defect area observed in samples from Batch 8 is an indication of stability. Taguchi with MPCI analysis led to the following optimal combination of parameters: addition of reinforcement pass two wt. % processed two passes, AZ61 and with an angle of 120° of ECAP MMCs were both deemed optimal and verified its results experimentally.
43
lee, Chih-yao, and 李智堯. "Study of effects of equal channel angular pressing with different angle and pass of AZ31/WS2 INT magnesium matrix composites on their microstructure and mechanical properties." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/hvmrgv.
Full textAbstract:
碩士<br>國立臺灣科技大學<br>機械工程系<br>106<br>The main purpose of this study is to use AZ31 magnesium alloy as matrix and use WS_2-INT as the strengthening phase to produce Magnesium-based composites. After T4 heat treatment, materials will be extruded with 90° and 120° ECAP dies. Disscusions of effects about different angle and pass of ECAP will be included in this study.
From the experimental results, it can be found that adding additional WS_2-INT in the matrix can effectively enhance the material's strength and ductility through grain refinement. Through T4 heat treatment, the β-Mg_17 Al_12 phase can be dissolved in the material and aluminum precipitates. The precipitation of this phase increase the ductility of the material. The multi-pass ECAP extrusion enables dynamic recrystallization of the material to refine the grain size and increase its ductility and tensile strength. However, due to the strain caused by the 90 degree ECAP is too large, the material cannot maintain good formability. Combined with XRD, EBSD analysis and tensile test results, the material shows different crystal orientations after different passes of ECAP. After two passes of ECAP, the crystal orientation of the material tends to [1 ̅21 ̅0] direction which makes the strongest yielding strength reach 164.3 MPa , and after four passes of ECAP, the crystal orientation of the material tends towards [0001] which which makes the strongest yielding strength only 114.1 MPa. The phenomenon of different crystal orientation is the main cause of the material with 4 passes of ECAP being inferior to the material of 2 passes ECAP.
44
Sun, Cheng. "Mechanical Properties and Radiation Tolerance of Ultrafine Grained and Nanocrystalline Metals." Thesis, 2013. http://hdl.handle.net/1969.1/149516.
Full textAbstract:
Austenitic stainless steels are commonly used in nuclear reactors and have been considered as potential structural materials in fusion reactors due to their excellent corrosion resistance, good creep and fatigue resistance at elevated temperatures, but their relatively low yield strength and poor radiation tolerance hinder their applications in high dose radiation environments. High angle grain boundaries have long been postulated as sinks for radiation-induced defects, such as bubbles, voids, and dislocation loops. Here we provide experimental evidence that high angle grain boundaries can effectively remove radiation-induced defects. The equal channel angular pressing (ECAP) technique was used to produce ultrafine grained Fe-Cr-Ni alloy. Mechanical properties of the alloy were studied at elevated temperature by tensile tests and in situ neutron scattering measurements. Enhanced dynamic recovery process at elevated temperature due to dislocation climb lowers the strain hardening rate and ductility of ultrafine grained Fe-Cr-Ni alloy. Thermal stability of the ultrafine grained Fe-Cr-Ni alloy was examined by ex situ annealing and in situ heating within a transmission electron microscope. Abnormal grain growth at 827 K (600°C) is attributed to deformation-induced martensite, located at the triple junctions of grains. Helium ion irradiation studies on Fe-Cr-Ni alloy show that the density of He bubbles, dislocation loops, as well as irradiation hardening are reduced by grain refinement. In addition, we provide direct evidence, via in situ Kr ion irradiation within a transmission electron microscope, that high angle grain boundaries in nanocrystalline Ni can effectively absorb irradiation-induced dislocation loops and segments. The density and size of dislocation loops in irradiated nanocrystalline Ni were merely half of those in irradiated coarse grained Ni. The results imply that irradiation tolerance in bulk metals can be effectively enhanced by microstructure refinement.
45
Sob, Peter Baonhe. "Modelling stain rate sensitive nanomaterials' mechanical properties: the effects of varying definitions." Thesis, 2016. http://hdl.handle.net/10352/332.
Full textAbstract:
M. Tech. (Mechanical Engineering, Faculty of Engineering and Technology): Vaal University of Technology<br>Presently there exist a lot of controversies about the mechanical properties of nanomaterials. Several convincing reasons and justifications have been put forward for the controversies. Some of the reasons are varying processing routes, varying ways of defining equations, varying grain sizes, varying internal constituent structures, varying techniques of imposing strain on the specimen etc. It is therefore necessary for scientists, engineers and technologists to come up with a clearer way of defining and dealing with nanomaterials’ mechanical properties. The parameters of the internal constituent structures of nanomaterials are random in nature with random spatial patterns. So they can best be studied using random processes, specifically as stochastic processes. In this dissertation the tools of stochastic processes have been used as they offer a better approach to understand and analyse random processes.
This research adopts the approach of ascertaining the correct mathematical models to be used for experimentation and modelling. After a thorough literature survey it was observed that size and temperature are two important parameters that must be considered in selecting the relevant mathematical definitions for nanomaterials’ mechanical properties. Temperature has a vital role to play during grain refinement since all severe plastic deformation involves thermomechanical processes.
The second task performed in this research is to develop the mathematical formulations based on the experimental observation of 2-D grains and 3-D grains deformed by Accumulative Roll-Bonding and Equal Channel Angular Pressing. The experimental observations revealed that grains deformed by Accumulative Roll-Bonding and Equal Channel Angular Pressing are elongated when observed from the rolling direction, and transverse direction, and equiaxed when observed from the normal direction. In this dissertation, the different experimental observations for the grain size variants during grain refinement were established for 2-D and 3-D grains. This led to the development of a stochastic model of grain-elongation for 2-D and 3-D grains.
The third task was experimentations and validation of proposed models. Accumulative Roll-Bonding, Equal Channel Angular Pressing and mechanical testing (tensile test) experiments were performed. The effect of size on elongation and material properties were studied to validate the developed models since size has a major effect on material’s properties.
The fourth task was obtaining results and discussion of theoretical developed models and experimental results.
The following facts were experimentally observed and also revealed by the models. Different approaches of measuring grain size reveal different strains that cannot be directly obtained from plots of the corresponding grain sizes. Grain elongation evolved as small values for larger grains, but became larger for smaller grains. Material properties increased with elongation reaching a maximum and started decreasing as is evident in the Hall-Petch to the Reverse Hall-Petch Relationship. This was alluded to the fact that extreme plastic straining led to distorted structures where grain boundaries and curvatures were in “non-equilibrium” states.
Overall, this dissertation contributed new knowledge to the body of knowledge of nanomaterials’ mechanical properties in a number of ways. The major contributions to the body of knowledge by his study can be summarized as follows:
(1) The study has contributed in developing a model of elongation for 2-D grain and 3-D grains. It has been generally reported by researchers that materials deformed by Accumulative Roll-Bonding and Equal Channel Angular Pressing are generally elongated but none of these researchers have developed a model of elongation. Elongation revealed more information about “size” during grain refinement.
(2) The Transmission Electron Microscopy revealed the grain shape in three directions. The rolling direction or sliding direction, the normal direction and the transverse direction. Most developed models ignored the different approaches of measuring nanomaterials’ mechanical properties. Most existing models dealt only with the equivalent radius measurement during grain refinement. In this dissertation, the different approaches of measuring nanomaterials’ mechanical properties have been considered in the developed models. From this dissertation an accurate correlation can be made from microscopy results and theoretical results.
(3) This research has shown that most of the published results on nanomaterials’ mechanical properties may be correct although controversies exist when comparing the different results. This research has also shown that researchers might have considered different approaches to measure nanomaterials’ mechanical properties. The reason for different results is due to different approaches of measuring nanomaterials’ mechanical properties as revealed in this research. Since different approaches of measuring nanomaterials’ mechanical properties led to different obtained results, this justify that most published results of nanomaterials’ mechanical properties may be correct. This dissertation revealed more properties of nanomaterials that are ignored by the models that considered only the equivalent length.
(4) This research has contributed to the understanding of nanomaterials controversies when comparing results from different researchers.