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1

Vasudevan, Satish. "AN INVESTIGATION OF QUASI-STATIC BEHAVIOR, HIGH CYCLE FATIGUE AND FINAL FRACTURE BEHAVIOR OFALUMINUM ALLOY 2024 AND ALUMINUM ALLOY 2219." Akron, OH : University of Akron, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1193668130.

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Thesis (M.S.)--University of Akron, Dept. of Mechanical Engineering, 2007.
"December, 2007." Title from electronic thesis title page (viewed 02/23/2008) Advisor, T. S. Srivatsan; Faculty readers, Craig Menzemer, Amit Prakash; Department Chair, Celal Batur; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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2

Qian, Daishu. "Microstructure and corrosion performance of excimer laser-melted AA2124-T4 aluminium alloy and SiCp/AA2124-T4 composite." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/microstructure-and-corrosion-performance-of-excimer-lasermelted-aa2124t4-aluminium-alloy-and-sicpaa2124t4-composite(705f8af9-2a7c-4188-91e4-fcf33d8f76f0).html.

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The present work studies the microstructure and corrosion behaviour of 25 vol.% SiCp/AA2124-T4 metal matrix composites (MMCs) and AA2124-T4 aluminium alloy; and also the capability of excimer laser surface melting (LSM) to improve the corrosion resistance of the SiCp/AA2124 MMC and the monolithic alloy (MA). Microstructural characterization has shown significant influence of the presence and size of SiC particles on the fine Al2Cu precipitate and Mg segregation at SiC/Al interfacial regions. Such precipitates are revealed to be active sites for corrosion initiation in the MMCs, while the preferential sites for corrosion initiation in the MA are the coarse intermetallics. Corrosion evaluation performed in a 0.6 M NaCl solution suggests that the corrosion resistance of the MMC reinforced with micrometre-sized SiC particles is inferior to that of the MA and the MMC reinforced with submicrometre-sized SiC particles. The submicrometre-sized SiC particles have little adverse effect on the corrosion resistance of the MMC due to the reduced interfacial precipitates. Thin films of up to several micrometres have been achieved by excimer LSM on both the MMC and the MA. The surface roughness and the thickness of the melted layer increase with increasing laser fluence. High number of pulses (40 P) results in significant porosity in the MA and networks of cracking in the MMC. A homogeneous layer without chemical segregation except the Cu-rich segregation bands has been obtained on the MA; while complex microstructures are observed for the MMC, including the Cu-rich segregation bands, Al-Si eutectic structure and microsegregation-free structure laid in sequence from the bottom of the melted layer to the top surface. The modelling work suggest that the presence of SiC particles gives rise in high temperatures in the melt pool, which is useful to explain the materials responses upon laser irradiation, such as decomposition of SiC, evaporation of matrix alloy, and oxides formation. The fast cooling rate up to 1011 K/s is responsible for the formation of microsegregation-free structure. Corrosion evaluation has indicated improvement of corrosion resistance of the MMC and the MA after excimer LSM due to the reduction of the intermetallics. For the laser-melted MA, the corrosion behaviour is governed by the surface morphology and the porosity. The significant rippled structure obtained under high laser fluence could lead to crevice corrosion in the valley between the ripples whilst the pores could provide penetrating routes for the chloride solution to reach the Cu-rich segregation bands, leading to the delamination of the melted layer. For the laser-melted MMC, corrosion mainly initiated at the SiC remnants, which are rich in Si. The corrosion sites of the laser-melted MMC are in the form of small cracked blisters.
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3

Poudel, Amir. "Dissimilar Joining of Al (AA2139) – Mg (WE43) Alloys Using Friction Stir Welding." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc955064/.

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This research demonstrates the use of friction stir welding (FSW) to join dissimilar (Al-Mg) metal alloys. The main challenges in joining different, dissimilar metal alloys is the formation of brittle intermetallic compounds (IMCs) in the stir zone affecting mechanical properties of joint significantly. In this present study, FSW joining process is used to join aluminum alloy AA2139 and magnesium alloy WE43. The 9.5 mm thick plates of AA2139 and WE43 were friction stir butt welded. Different processing parameters were used to optimize processing parameters. Also, various weldings showed a crack at interface due to formation of IMCs caused by liquation during FSW. A good strength sound weld was obtained using processing parameter of 1200 rev/min rotational speed; 76.2 mm/min traverse speed; 1.5 degree tilt and 0.13 mm offsets towards aluminum. The crack faded away as the tool was offset towards advancing side aluminum. Mostly, the research was focused on developing high strength joint through microstructural control to reduce IMCs thickness in Al-Mg dissimilar weld joint with optimized processing parameter and appropriate tool offset.
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4

Padgett, Barbara Nicole. "Investigation into the stress corrosion cracking properties of AA2099, an Al-Li-Cu alloy." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1204515486.

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5

Jurak, Sarah F. "Statistical analysis of the mechanical properties of Friction Stir Welded AA2024 and AA2198 aluminum alloys." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/5181.

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This thesis presents an analysis of data based on the results of a previous study into the path independence of friction stir welding (FSW). The original study was conducted in two phases using AA2024 and AA2198 aluminum alloy material. In Phase I, welds were made with six different tool designs, and tensile data was entered into Statgraphics® software as part of a design of experiments (DOE) approach for the purpose of optimizing the weld parameter process windows for each tool design. Phase II included a round robin study where welds were produced at four sites to evaluate site-to-site variability. In the present study, testing of the welds included additional tensile testing, full-field microhardness testing, and conductivity testing of the welds produced in the prior two phases of the program. The welds were inspected for defects, and the method of failure on the tensile specimens is discussed. Tensile data was evaluated statistically using Statgraphics® software. Previously, as part of Phase I, that data was evaluated using the techniques of chapter nine of the Metallic Materials Properties Development and Standardization (MMPDS), and design allowables were calculated at that time. In the present study, Phase II data was compared using the design allowables from Phase I. Variability was not found to be significant when evaluated according to location of the tensile coupon along the weld joint line or as a function of weld parameters in the process window. Although site-to-site variability was significant, it was low, with the highest variation for each material being 2 to 5.5 ksi. No significant outliers were identified. There is evidence that the friction stir welding process is path-independent and that a defect-free weld is uniform in tensile strength from beginning to end. There is also evidence that a DOE approach can be used to optimize the weld parameter process window for any tool in order to identify a range of weld parameters where a defect-free weld can be produced.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
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6

Klages, Holli K. "The "Lazy S" feature in Friction Stir Welding of AA2099 Aluminum-Lithium alloy." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Dec%5FKlages.pdf.

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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2007.
Thesis Advisor(s): McNelley, Terry. "December 2007." Description based on title screen as viewed on January 22, 2008. Includes bibliographical references (p.45). Also available in print.
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7

Hanna, Benjamin. "Investigation Into the Localized Corrosion of Aluminum-Copper-Lithium Alloy 2099." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534749550969422.

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8

Reed, Jordan Derek. "Ultrasonic Processing of Aluminum 2139 and 7050." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1248496/.

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Acoustics is the study of all sound waves, with ultrasound classified as those frequencies above 20,000 Hz. Currently, ultrasound is being used in many industries for a variety of purposes such as ultrasonic imaging, ultrasonic assisted friction stir welding, and ultrasonic spot welding. Despite these uses, the effects of ultrasound on phase stability and resultant mechanical properties has been minimally analyzed. Here we study the impact waves play in ultrasonic welding and design an apparatus to maximize waves entering aluminum alloy samples. Aluminum 2139 and 7050 are used because they are precipitation strengthened by metastable phases so temperature change, and the corresponding phase stability, can greatly impact their strength. Results suggest that the ultrasonic welder primarily imposes a localized temperature spike due to friction, averaging over 200°C in a few seconds, which generally lowers the Vickers hardness due to coarsening or even dissolution of strengthening precipitates. Conversely, the new design increases the Vickers hardness by up to 30% over the initial hardness of approximately 63HV for aluminum 2139 and 83HV for aluminum 7050, respectively, while only increasing the temperature by an average of approximately 10°C. This new design was unable to achieve peak hardness, but the strengthening it achieved in two minutes was equivalent to one month of natural aging. If this system was able to be fine-tuned, it could serve as a quick strengthening process for recently weakened aluminum alloys, such as after friction stir welding.
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9

Silva, Renato Rafael 1983. "Produção de esponjas metalicas por tixoconformação em pre-formas removiveis e sua caracterização mecanico-metalurgica." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263601.

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Orientador: Maria Helena Robert
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-11-08T18:39:47Z (GMT). No. of bitstreams: 1 Silva_RenatoRafaelda_M.pdf: 15646556 bytes, checksum: 19ff8cd2fd9081ac7985bc44c94795f5 (MD5) Previous issue date: 2008
Resumo: Este trabalho teve como objetivo estudar o processo de produção de esponjas metalicas por tixoconformacao em pré-formas removiveis e caracterizacao mecanico-metalurgica do produto, visando a compreensão da influencia de parametros de processo nas suas caracteristicas estruturais e propriedades. A liga empregada, AA2011, foi infiltrada sobre pre-formas de particulas de NaCl de granulometrias distintas, sinterizadas ou soltas. As esponjas metalicas produzidas foram caracterizadas quanto a sua arquitetura, propriedades fisicas (densidade real e relativa, condutividade e difusividade termicas) e mecanicas (tensão de compressão, modulo de Young, tensão no plato, deformação e energia de impacto absorvida); foi analisada a influencia do tipo de pre-forma utilizada para produção das esponjas, nestas caracteristicas e propriedades. Os resultados mostraram boa reprodutibilidade do processo, principalmente quando da utilização de pre-formas de partículas medias e grosseiras nao sinterizadas. A densidade da esponja e a espessura da parede celular apresentam tendencia a aumentar com o aumento das dimensões das celulas produzidas em preformas de particulas mais grosseiras. Todas as amostras produzidas apresentaram condutividade termica da ordem de 10x inferior e difusividade termica da ordem de 4x superior as do metal maciço. O comportamento das esponjas em compressão estatica ou dinamica se mostrou tipico de materiais celulares, com reduzidos valores de modulo de Young e de tensão de compressão, grande plato de deformação plástica sem acréscimo de tensão, e elevados valores de deformação total e energia absorvida no impacto
Abstract: The aim of this work was the analysis of the thixoforming process to produce metallic sponges and the mechanical and metallurgical characterization of the product, searching for better understanding the influence of processing parameters in the material structural characteristics and properties. The aluminium alloy AA2011 was infiltrated in the semi-solid state into performs of NaCl particles with different sizes and in sintered and non sintered conditions. Cellular products were characterized concerning internal architecture, physical properties (actual and relative densities, thermal conductivity and diffusivity) and mechanical properties (Young's modulus, compressive strength, plateau stress and absorbed impact energy); it was analyzed the influence of processing parameters on the properties and characteristics of the produced sponges. Results showed good reproducibility of the process, mainly when medium and coarse non sintered space holder particles were employed. Density of the product as well as cell wall thickness increases as space holder particles sizes increase. All the sponges produced showed low thermal conductivity (~10x inferior compared to the bulk material) and high thermal diffusivity (~3x superior compared to the bulk alloy). Results of static and dynamic compression tests showed typical cellular material behaviour in all cases, presenting low values for Young's modulus and compressive strength, a well defined plateau of plastic deformation, high plastic deformation and high capacity of energy absorption in impact events
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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10

Narayanan, P. Ramesh. "A Study Of Crystallographic Texture, Residual Stresses And Mechanical Property Anisotropy In Aluminium Alloys For Space Applications." Thesis, 2010. https://etd.iisc.ac.in/handle/2005/1999.

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Aluminium alloys, which are the most widely used materials in the aircraft and aerospace industries, find their applications due to high strength–to-density ratio, resistance to catastrophic fracture, high degree of toughness, fabricability including good weldability and availability. High strength aluminum alloys are used in different forms like sheets, forgings and extruded rods, welded and machined components in the aerospace industry. One major application of the aluminium alloys in the space sector is in the launch vehicle and satellite sub-systems. The Indian Space Research Organization has met major challenges of indigenization of suitable aluminium alloys, for example, Al-Cu alloys (like AA2219) and Al–Zn-Mg alloys (like AA7075 and AFNOR 7020). Many failures of the metallic sub-systems made of different grades of aluminum alloys have confirmed that high levels of residual stresses and unacceptable microstructures have played a role. Crystallographic texture in these materials has a very significant role to play in the performance of these materials in service. The anisotropy in the mechanical properties caused by crystallographic texture would add to the woes of the existing problems of residual stresses and directionality in the microstructure. In this context, a detailed study of crystallographic texture and residual stresses of high strength aluminium alloys is mandatory. It is also important to study the influence of texture on the anisotropy in mechanical properties. The present research programme aims at addressing some of these aspects. The entire work has been divided in three major sections, namely macro and micro texture analysis, non-destructive measurement of residual stresses using X-ray Diffraction (XRD) and the Ultrasonic Testing (UST) and the study of anisotropy in the mechanical properties arising due to the above two factors. The thesis composition is as follows. In Chapter I, a detailed survey of the literature has been presented wherein basic physical metallurgy for different aluminum alloys of interest has been given. Thereafter, details of texture measurement by the X-ray diffraction and Electron Back Scatter Diffraction (EBSD) are presented. This is followed by a detailed review on the texture studies carried out in aluminium alloys under various conditions. Literature review on the two non-destructive methods, namely the X-ray diffraction and ultrasonic method has been carried out in detail. In order to account for microstructural changes, Differential Scanning Calorimetry (DSC) was carried out. Recent work on the mechanical property anisotropy arising due to high degree of mechanical working in aluminium alloys has been reviewed. Chapter II includes the experimental details involved in the course of the present investigation. The procedural details of cold rolling and associated microstructural changes are given in this chapter. This is followed by the texture measurement methods. Experimental details of the bulk texture measurement using the X-ray diffraction and micro texture measurements by the Electron Back Scatter Diffraction (EBSD) in the SEM are described. Details of the texture computation procedure as well as micro texture analysis methods are also presented. Basic principles of the non-destructive methods of measuring residual stresses, viz., the X-ray diffraction and the Ultrasonic testing, including the theory of measurements, are dealt with. Finally, the details of measurements of anisotropy in mechanical properties, including simulation carried out, for the three alloys are delineated. Chapter III deals with the results of the crystallographic texture measurements carried out on the cold rolled and artificially aged aluminium alloys. Results obtained from the pole figure analysis, Orientation Distribution Function (ODF) method and estimation of the various fibres present in the cold rolled material and the volume fraction of the texture components are discussed in detail for the three aluminium alloys. Results of the micro texture measurements using the EBSD are presented, explained and analyzed in detail. A comparison of the inverse pole figures (IPFs), Image Quality (IQ) maps, Misorientation angle, Grain Orientation Spread (GOS), Kernal Average Misorientation (KAM), CSL boundaries, Grain size and Grain boundary character distribution (GBCD) for materials cold rolled to different reduction for each of the alloys are done and analyzed. Conclusions are drawn regarding the evolution of texture from the above analysis. Deformation texture components Cu, Bs and S increase from the starting material as the rolling percentage increases. On the other hand, recrystallization texture components of Goss and Cube are observed to be weak. AFNOR 7020 developed the strongest texture followed by the AA7075 and AA2219 alloys. The Bs component is stronger in AFNOR 7020 alloy. This is attributed to the shear banding. Average KAM value increases as the cold working in the material increases confirming that the material contains high dislocation density at higher working percentages. Chapter IV deals with residual stresses in the aluminium alloys. Measurement of residual stresses has been carried out on the same sheets and plates, wherever it was possible, using the two methods. The residual stresses have been measured in two mutually perpendicular directions of the aluminium alloy sheets. Residual stress measurements by the ultrasonic method using the Critically Refracted Longitudinal (LCR) wave technique is also used to measure the subsurface stresses non-destructively. Acousto Elastic Coefficients (AEC) is determined for the alloys, in uniaxial tension. Using the AEC for the alloys, the RS at a depth of 3mm are evaluated using a 2MHz probe. Results of the stresses measured by the two methods have been discussed. The trends and anisotropy in the stress values due to texture are discussed and compared with the literature available. Surface residual stresses by the XRD method show compressive stresses at a majority of the locations. Residual stresses measured by the ultrasonic technique, which has a depth of penetration of about 3mm, have shown tensile stresses on many locations. Residual stresses are influenced by the crystallographic texture. Anisotropy in stress values in the longitudinal and transverse directions is demonstrated. In Chapter V, the anisotropy in mechanical properties for the three alloys is discussed in detail. The anisotropy in the three directions, namely the parallel, transverse and 45 deg orientation to the rolling directions is evaluated. The Lankford parameter, otherwise known as Plastic Anisotropy Ratio “r”, has been measured from the tensile tests of the alloy samples in the cold rolled conditions. These have been compared with the computed “r” from the XRD ODF data using the VPSC simulations and found to be qualitatively matching. These trends are discussed with the available literature on the anisotropy of the mechanical properties for aluminium alloys. Samples subjected to high cold rolling show anisotropy of UTS, YS and ‘n’ values. Experimentally measured “r” values in all the deformation conditions match the trend qualitatively with the simulated ones. The maximum anisotropy was observed at 45o orientation to the rolling direction in all the three alloys. Chapter VI gives the summary of the results from the study and the suggestions for future work.
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11

Narayanan, P. Ramesh. "A Study Of Crystallographic Texture, Residual Stresses And Mechanical Property Anisotropy In Aluminium Alloys For Space Applications." Thesis, 2010. http://etd.iisc.ernet.in/handle/2005/1999.

Full text
Abstract:
Aluminium alloys, which are the most widely used materials in the aircraft and aerospace industries, find their applications due to high strength–to-density ratio, resistance to catastrophic fracture, high degree of toughness, fabricability including good weldability and availability. High strength aluminum alloys are used in different forms like sheets, forgings and extruded rods, welded and machined components in the aerospace industry. One major application of the aluminium alloys in the space sector is in the launch vehicle and satellite sub-systems. The Indian Space Research Organization has met major challenges of indigenization of suitable aluminium alloys, for example, Al-Cu alloys (like AA2219) and Al–Zn-Mg alloys (like AA7075 and AFNOR 7020). Many failures of the metallic sub-systems made of different grades of aluminum alloys have confirmed that high levels of residual stresses and unacceptable microstructures have played a role. Crystallographic texture in these materials has a very significant role to play in the performance of these materials in service. The anisotropy in the mechanical properties caused by crystallographic texture would add to the woes of the existing problems of residual stresses and directionality in the microstructure. In this context, a detailed study of crystallographic texture and residual stresses of high strength aluminium alloys is mandatory. It is also important to study the influence of texture on the anisotropy in mechanical properties. The present research programme aims at addressing some of these aspects. The entire work has been divided in three major sections, namely macro and micro texture analysis, non-destructive measurement of residual stresses using X-ray Diffraction (XRD) and the Ultrasonic Testing (UST) and the study of anisotropy in the mechanical properties arising due to the above two factors. The thesis composition is as follows. In Chapter I, a detailed survey of the literature has been presented wherein basic physical metallurgy for different aluminum alloys of interest has been given. Thereafter, details of texture measurement by the X-ray diffraction and Electron Back Scatter Diffraction (EBSD) are presented. This is followed by a detailed review on the texture studies carried out in aluminium alloys under various conditions. Literature review on the two non-destructive methods, namely the X-ray diffraction and ultrasonic method has been carried out in detail. In order to account for microstructural changes, Differential Scanning Calorimetry (DSC) was carried out. Recent work on the mechanical property anisotropy arising due to high degree of mechanical working in aluminium alloys has been reviewed. Chapter II includes the experimental details involved in the course of the present investigation. The procedural details of cold rolling and associated microstructural changes are given in this chapter. This is followed by the texture measurement methods. Experimental details of the bulk texture measurement using the X-ray diffraction and micro texture measurements by the Electron Back Scatter Diffraction (EBSD) in the SEM are described. Details of the texture computation procedure as well as micro texture analysis methods are also presented. Basic principles of the non-destructive methods of measuring residual stresses, viz., the X-ray diffraction and the Ultrasonic testing, including the theory of measurements, are dealt with. Finally, the details of measurements of anisotropy in mechanical properties, including simulation carried out, for the three alloys are delineated. Chapter III deals with the results of the crystallographic texture measurements carried out on the cold rolled and artificially aged aluminium alloys. Results obtained from the pole figure analysis, Orientation Distribution Function (ODF) method and estimation of the various fibres present in the cold rolled material and the volume fraction of the texture components are discussed in detail for the three aluminium alloys. Results of the micro texture measurements using the EBSD are presented, explained and analyzed in detail. A comparison of the inverse pole figures (IPFs), Image Quality (IQ) maps, Misorientation angle, Grain Orientation Spread (GOS), Kernal Average Misorientation (KAM), CSL boundaries, Grain size and Grain boundary character distribution (GBCD) for materials cold rolled to different reduction for each of the alloys are done and analyzed. Conclusions are drawn regarding the evolution of texture from the above analysis. Deformation texture components Cu, Bs and S increase from the starting material as the rolling percentage increases. On the other hand, recrystallization texture components of Goss and Cube are observed to be weak. AFNOR 7020 developed the strongest texture followed by the AA7075 and AA2219 alloys. The Bs component is stronger in AFNOR 7020 alloy. This is attributed to the shear banding. Average KAM value increases as the cold working in the material increases confirming that the material contains high dislocation density at higher working percentages. Chapter IV deals with residual stresses in the aluminium alloys. Measurement of residual stresses has been carried out on the same sheets and plates, wherever it was possible, using the two methods. The residual stresses have been measured in two mutually perpendicular directions of the aluminium alloy sheets. Residual stress measurements by the ultrasonic method using the Critically Refracted Longitudinal (LCR) wave technique is also used to measure the subsurface stresses non-destructively. Acousto Elastic Coefficients (AEC) is determined for the alloys, in uniaxial tension. Using the AEC for the alloys, the RS at a depth of 3mm are evaluated using a 2MHz probe. Results of the stresses measured by the two methods have been discussed. The trends and anisotropy in the stress values due to texture are discussed and compared with the literature available. Surface residual stresses by the XRD method show compressive stresses at a majority of the locations. Residual stresses measured by the ultrasonic technique, which has a depth of penetration of about 3mm, have shown tensile stresses on many locations. Residual stresses are influenced by the crystallographic texture. Anisotropy in stress values in the longitudinal and transverse directions is demonstrated. In Chapter V, the anisotropy in mechanical properties for the three alloys is discussed in detail. The anisotropy in the three directions, namely the parallel, transverse and 45 deg orientation to the rolling directions is evaluated. The Lankford parameter, otherwise known as Plastic Anisotropy Ratio “r”, has been measured from the tensile tests of the alloy samples in the cold rolled conditions. These have been compared with the computed “r” from the XRD ODF data using the VPSC simulations and found to be qualitatively matching. These trends are discussed with the available literature on the anisotropy of the mechanical properties for aluminium alloys. Samples subjected to high cold rolling show anisotropy of UTS, YS and ‘n’ values. Experimentally measured “r” values in all the deformation conditions match the trend qualitatively with the simulated ones. The maximum anisotropy was observed at 45o orientation to the rolling direction in all the three alloys. Chapter VI gives the summary of the results from the study and the suggestions for future work.
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12

Shunmugam, Sree Sabari. "EVALUATION OF PERFORMANCE OF FRICTION STIR WELDED AA2519-T87 ALUMINIUM ALLOY JOINTS." Doctoral thesis, 2016. http://hdl.handle.net/10316/80734.

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13

Sharma, Prince. "Ballistic impact behaviour of aluminium alloy AA2014-T652 subjected to rigid and deformable projectiles." Thesis, 2017. http://localhost:8080/xmlui/handle/12345678/7261.

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14

Rodrigues, Diogo Farias Gonçalves Alexandre. "Plasma nitriding of AA2011 alloy and surface characterization by NDT techniques." Master's thesis, 2015. http://hdl.handle.net/10362/16443.

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Al-Cu alloys are widely used in the aerospace and automotive industries due to their high specific strength in some tempered conditions. However, due to poor corrosion and wear resistance, they are often anodized and/or painted. Plasma nitriding has been proposed as an alternative, though the developments in this technique are still in a recent stage for Al alloys. Electrical characterization techniques are well implemented NDTs in the industry because of good accuracy associated with lower cost, compared to other methods. Some, like eddy currents and 4-point probe techniques, are often used in coating inspection. The objective of this study was to perform Al nitriding at low temperatures to minimize the tempering initial condition damage and to assess the feasibility of eddy currents technique as a method for evaluating surface properties. The work developed can be divided in two stages. The first one was the process tuning, done at the Shibaura Institute of Technology, in Tokyo; and the second was the electrical characterization done in Faculdade de Ciências e Tecnologia, UNL. Low temperature nitriding of AA2011 alloy specimens was successfully achieved. Electrical conductivity results show that lift-off measurements by eddy currents testing can be related to surface properties.
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15

More, Abhishek Mukund. "Effect of processing on texture and microstructure in Aluminium-Lithium alloys and its consequences on mechanical properties." Thesis, 2018. https://etd.iisc.ac.in/handle/2005/5365.

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Lightweight Aluminium -Lithium based alloys have high potential for use in aerospace structural components. However, large anisotropy in mechanical properties restricts the use of these alloys. The alloy AA2195 (Al-Li-Cu-Mg-Ag-Zr) is the third generation Al-Li based alloy which is viewed as the most promising choice for structural aerospace applications among the other Al-Li alloys. However, even in this alloy, the combined effect of crystallographic texture and heterogeneous distribution of precipitates leads to mechanical property anisotropy, which is highly undesirable for the formability of this alloy. This underscores the need for developing suitable processing strategies for overcoming the problem of anisotropy. The present thesis aims at exploring the possibilities to improve the mechanical properties and reduce anisotropy in the material by tailoring texture and microstructure in the alloy AA2195 also by designing newer processing schedules and by suitable alloying addition. For this, in the present investigation, texture and microstructure of an already hot rolled plate of AA2195 was modified by employing various types of cross rolling in the processing schedule vis-à-vis an identical processing schedule involving normal unidirectional rolling and the consequent evolution of mechanical properties was examined. The change in strain path led to the formation of weak texture, and a reduction in the degree of anisotropy from 24 % in the as-received hot rolled material to as low as 5 % in the materials processed through routes involving cross rolling. Further, the differently textured sheets were subjected to incremental forming. It was observed that texture weakening by change in the strain path during rolling led to a significant improvement in the formability of the alloy during incremental sheet forming. In the subsequent chapter, further attempts for weakening the texture though a route involving multi-axial forging (MAF) of the cast material were made and consequent evolution of anisotropy in mechanical properties was evaluated. It has been observed that incorporation of multi-axial forging in the processing schedule has led to further weakening of texture. In the next chapter, the effect of severe plastic deformation by Equal Channel Angular Pressing (ECAP) has been examined on the evolution of texture and microstructure and the effect of this process on improvement in mechanical properties has been reported with the detailed explanation of the mechanism. In the next chapter, which aims at suitably modifying the chemistry of the alloy AA2195 by alloying, the effect of scandium (Sc) addition to AA2195 has been studied with special emphasis on the evolution of texture and microstructure during calibre rolling. Addition of Sc has led to enhancement in the degree of grain refinement compared with AA2195 alloy without Sc, when processed using calibre rolling. Finally, it has been concluded that suitable modifications in the processing schedule and the composition modulates the microstructure and texture thereby, improving the mechanical properties
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16

Ragupathy, V. D. "Studies on Non-Destructive Evaluation of Friction Stir Weld Discontinuities with Probability of Detection." Thesis, 2018. https://etd.iisc.ac.in/handle/2005/5323.

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Abstract:
Friction stir welding(FSW) is a solid-state metal joining process which is currently being considered for joining of aerospace components. The zones associated with FSW are distinctly different from the fusion weld and their properties also vary. Further, the discontinuities and defects encountered are unique in nature. As most aerospace components are designed with limited margin, the identification of the Friction stir weld defects and discontinuities, and their effect on the performance pose continuous challenges for the quality assessment. Thus, detection, location and characterization of different types of defects encountered in FSW, along with Probability of Detection (POD) of those discontinuities in aerospace friction stir welded components with its varying metallurgical characteristics are the primary objectives of the investigations taken up. The focus has been on capability of different NDE tools in detecting and evaluating different types of defects in FSW joints in the Aluminum alloy AA2219 and to establish the outcome through POD concept.
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