Download or read book Mechanical Property Microstructural and Textural Development During the High Temperature Slow Strain Rate Deformation of Al Li Cu Mg Zr Alloy AA8090 written by Paul Leslie Blackwell and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Index to Theses with Abstracts Accepted for Higher Degrees by the Universities of Great Britain and Ireland and the Council for National Academic Awards written by and published by . This book was released on 1998 with total page 922 pages. Available in PDF, EPUB and Kindle. Book excerpt: Theses on any subject submitted by the academic libraries in the UK and Ireland.

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1995 with total page 502 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Texture and Microstructure Development in Al 2 Mg During High Temperature Deformation written by and published by . This book was released on 1990 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: The high rate sensitivity of the flow stress that is exhibited by alloys under solute drag control, such as Al-Mg at high temperatures, influences texture development because more slip systems contribute to deformation. Al-2% Mg was tested in channel-die compression, i.e. idealized rolling, at 290°C and 400°C, at strain rates from 10−1/s to 10−5/s. The texture development in rolling predicted by polycrystal plasticity simulation indicates that the brass component increases while the copper component decreases when the rate sensitivity is raised. The experimental results are in good agreement with this prediction. In addition, cube component appears when microstructural change occurs due to dynamic recrystallization. This microstructural change leads to the shift from {l angle}011{r angle} to {l angle}001{r angle} fiber texture in free compression at high temperature. 18 refs., 13 figs.

Download or read book Metals Abstracts Index written by and published by . This book was released on 1995 with total page 1390 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High Temperature Deformation Behaviour of an Al Mg Si Cu Alloy and Its Relation to the Microstructural Characteristics written by Roger Nicol Carrick and published by . This book was released on 2009 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: The microstructural evolution and mechanical properties at elevated temperatures of a recently fabricated fine-grained AA6xxx aluminium sheet were evaluated and compared to the commercially fabricated sheet of the same alloy in the T4P condition. The behaviour of the fine-grained and T4P sheets was compared at elevated temperatures between 350°C and 550°C, as well as room temperature. Static exposure to elevated temperatures revealed that the precipitate structure of the fine-grained material did not change extensively. The T4P material, however, underwent extensive growth of precipitates, including a large amount of grain boundary precipitation. At room temperature, the T4P material deformed at much higher stresses than the FG material, but achieved lower elongations. Deformation at elevated temperatures revealed that the fine-grained material achieved significantly larger elongations to failure than the T4P material in the temperature range of 350°C-450°C. Both materials behaved similarly at 500°C and 550°C. Above 500°C, the grain size was greatly reduced in the T4P material, and only a slightly increased in the fine-grained material. At temperatures above 450°C, the elongation to failure in both materials generally increased with increasing strain-rate. The poor performance of the T4P material at low temperatures was attributed to the precipitate characteristics of the sheet, which lead to elevated stresses and increased cavitation. The deformation mechanism of both materials was found to be controlled by dislocation climb, accommodated by the self diffusion of aluminium at 500°C and 550°C. The deformation mechanism in the fine-grained material transitioned to power law breakdown at lower temperatures. At 350°C to 450°C, the T4P material behaved similarly to a particle hardened material with an internal stress created by the precipitates. The reduction in grain size of the T4P material after deformation at 500°C and 550°C was suggested to be caused by dynamic recovery/recrystallization. The role of a finer grain-size in the deformation behaviour at elevated temperatures was mainly related to enhanced diffusion through grain boundaries. The differences in the behaviour of the two materials were mainly attributed to the difference in the precipitation characteristics of the materials.

Download or read book Effect of Temperature and Strain Rate on Microstructure of a Deformed Superplastic Al 10 Mg 0 1 Zr Alloy written by D. B. Berthold and published by . This book was released on 1985 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt: Development of microstructure during thermomechanical processing of an Al-10%Mg-O,1%Zr alloy was examined in the initial portion of this research. The thermomechanical processing involved solution treating; not working by upset forging at 440 C followed by warm rolling material were deformed at three strain rates at temperatures of 200 C, 300 C, and 400 C and were microstructurally examined. It is found that this alloy statically recrystallizes prior to commencing a test at 400 C, the resultant grains deform by boundary sliding and there is extensive cavitation. During lower temperature deformation it was found that either continuous recrystallization or just with no recrystallization occurs and little or no cavitation takes place.

Download or read book Physics Briefs written by and published by . This book was released on 1994 with total page 916 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Zr and V on Microstructure and Hot Deformation Behavior of 7150 Aluminum Alloys written by Cangji Shi and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Après avoir été allié avec du Zr de 0 à 0,19% en poids, les résultats ne montrent pas de variation significative du pic de la contrainte d'écoulement ou de l'énergie d'activation entre l'alliage de base 7150 et l'alliage contenant 0,04% en poids de Zr.

Download or read book Microstructural Deformation and Failure of an Al Mg Alloy with a Bimodal Grain Size Distribution written by Andrew C. Magee and published by . This book was released on 2014 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Strain and Strain Rate on the Microstructure of a Superplastically Deformed Al 10 Mg 0 1 Zr Alloy written by M. E. Alcamo and published by . This book was released on 1985 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt: The deformation characteristics of two thermomechanically processed, high-Magnesium, Aluminum-Magnesium-Zirconium alloys were investigated. The processing included warm rolling at 300 C to 90-95% reduction. Tension testing was done at various temperatures and strain rates and superplastic elongations were observed for both alloys. Subsequently, samples of A1-10%Mg-0.1% Zr were tested at 300 C to strains ranging from 8% to 267% as well as to fracture. Strain rates of .00667/S and .000667/s were used. These were examined via TEM to observe microstructural changes which occur during deformation. Quantitative analysis of the functional relationship between stress, strain, strain rate, and grain size for this alloy is done in an attempt to fit it's deformation response to current models for superplastic deformation.

Download or read book Effect of Alloy Composition on the Hot Deformation Behavior Extrudability and Mechanical Properties of AA6XXX Aluminum Alloys written by Daniel Oghenekewhe Odoh and published by . This book was released on 2017 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: As automotive companies adjust to stricter environmental legislations, there is increased interest in the application of high specific strength alloys such as the AA6xxx aluminum alloys. In the near term, light weighting of vehicles through the use of high strength aluminum alloys is one solution to improve fuel efficiency. This research was performed to help understand the extrudability of some Al-Mg-Si alloys as well as the effect of extrusion conditions on final mechanical properties. The alloys studied were designed by General Motors (GM) and include variations in the Mg, Si and Cr contents. The research is primarily experimental in nature and consisted of measuring and modelling the hot flow stress behaviour of these alloys, performing both laboratory scale and industrial extrusion trials as well as mechanical and microstructural characterization of the extruded materials. The well-known Sellars-Tegart model was applied in development of constitutive equations for predicting the hot flow stress behavior of Al-Mg-Si alloys. The influence of hold time on Mg-Si solute content level during pre-deformation heating of an as-cast and homogenized Al-Mg-Si alloy was determined and the Mg-Si solute content (X) integrated into a constitutive equation for predicting the alloy's flow stress behavior during hot compression testing. The constitutive model predictions were observed to agree well with experimental data for the aluminum alloys tested in this research. The effect of extrusion processing condition, alloy composition and aging time on the extrudability, mechanical properties and fracture morphology as well as microstructure of Al-Mg-Si alloys was studied. The extrudability of the Al-Mg-Si alloys was observed to reduce with an increase in the Mg-Si content, presence of 0.2 wt % Cr and reduction in extrusion temperature. For laboratory extrusion trials, peripheral coarse grains were not observed in alloys containing Cr and Mn. The strength property in the T4, T5 and T6 conditions was observed to increase with Mg-Si content while 0.2 wt % Cr addition favors improved ductility. The alloys containing Cr were observed to exhibit ductile dimple fracture and a transgranular morphology while an intergranular fracture was observed in the Al-Mg-Si alloys with no Cr content. The strain rate sensitivity and anisotropic behaviors of an Al-Mg-Si alloy were determined by performing quasi-static tensile test at 0.001, 0.01 and 0.1 s-1 on heat treated (T4 and T6) profiles extruded in industrial scale extrusion equipment. The T4 alloy samples were observed to exhibit reduced anisotropic behavior in comparison with T6 samples. In this thesis, a more effective constitutive model for predicting the hot flow stress behavior of Al-Mg-Si alloys has been developed. The developed constitutive relation can be an effective tool for modeling forming processes such as extrusion and rolling, Also, a systematic through process (from extrusion processing to aging) investigation of the effect of alloy composition, extrusion and aging conditions on the final mechanical properties of Al-Mg-Si alloys has been performed.

Download or read book Effect of Composition and Processing on the Microstructure and Formability of Aluminium Automotive Body Sheet Alloys written by Hao Zhong and published by . This book was released on 2014 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stretch forming is a common deformation mode during the stamping of 6xxx series Al-Mg-Si(-Cu) automotive body panels. Good formability in this mode requires high work hardening and strain rate hardening capabilities, which are controlled by the alloy composition and processing (particularly heat treatments) through their influence on the microstructure. The influence of composition and heat treatment on the formability of 6xxx alloys has been previously investigated, but systematic research is still needed in order to provide a deeper understanding of the underlying mechanisms for the purpose of maximising the formability of 6xxx alloys, whenever possible, by composition and heat treatment modifications. Therefore, in this PhD project, the effects of alloy composition (Si, Mg and Cu contents) and heat treatment (natural ageing and/or pre-ageing at 100 oC for 2 h or at 200 oC for 20 s) on the formability of eight 6xxx alloys were systematically studied. The microstructure of these alloys was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The macro-texture was characterised by X-ray diffraction. A surface profilometer was used to characterise the strain localisation. Tensile testing was used to determine the uniaxial tensile properties, and to study the work hardening and strain rate hardening behaviour of these alloys, which were used to correlate the microstructural features with the formability results. The use of Kocks-Mecking-Estrin model enabled a separation of the contributions of different microstructural features to the work hardening capability of the alloys studied. Furthermore, based on the knowledge from the experimental and constitutive modelling results, thermodynamic modelling was employed to predict the microstructure that could improve the formability of a high Mg content alloy. In this work it was found that solutes in solution are the most important factor that influences the stretch formability. It increases the work hardening capability by increasing the dislocation storage rate and impeding the dynamic recovery. For instance, Cu atoms were found to have a significant influence on the dislocation storage rate while having little influence on the dynamic recovery rate; conversely, Mg atoms have a substantial influence on the dynamic recovery rate while having little effect on the dislocation storage rate; and, finally, Si atoms have a slight influence on both the dynamic recovery rate and the dislocation storage rate. It should be noted that increasing Si content also leads to a high number density of dispersoids, although the contribution of dispersoids to work hardening is much smaller than that of solute atoms in solution. In terms of strain rate hardening behaviour, solute atoms in solution (particularly Mg atoms) reduce the strain rate sensitivity (SRS). However, if the addition of solutes promotes the natural ageing kinetics, then a high SRS is observed after extended natural ageing. This is the case in the high Si content alloys. By contrast, high Mg content alloys normally show a sluggish natural ageing kinetics, thus a larger negative contribution to SRS associated with dynamic strain ageing (DSA) can be observed. It was also found that Cu additions can retard the natural ageing kinetics regardless of the magnitude of the Mg/Si ratio in the alloys. The degree of retardation does depend on the Mg/Si ratio, though. This is particularly the case in the alloys with a high Mg/Si ratio where serrated yielding can still be observed in the alloy after one week of natural ageing. This is at variance with other alloys where serrated yielding disappeared within one day of natural ageing after quenching, which can be associated with the depletion of solutes and quenched-in vacancies. Vacancies were also found to influence the formability. This is particularly important in pre-aged samples. After one week of natural ageing, pre-aged samples showed a lower SRS than those without pre-ageing, which is probably due to a higher vacancy concentration in the pre-aged samples. The excess vacancies may exist as solute-vacancy complexes or be bound with solute clusters depending on pre-ageing time. A model was proposed to account for the decreased SRS in the pre-aged samples. Stretch formability is a property that is crucial in the selection of Al alloys for targeted applications. It was investigated in the course of the project in great detail. The overall effect of the alloy composition on the formability is that increasing Si content or decreasing Mg/Si ratio can improve the stretch formability due to the increased work hardening and strain rate hardening capabilities. The addition of Cu can significantly enhance the stretch formability of alloys with Mg/Si > 1, which is because the magnitude of the work hardening is more important than that of the strain rate hardening. An important property that influences acceptance of an alloy of the 6xxx series by industry is its bake-hardening response. This aspect of alloy development was also studied in the thesis. It was shown that although pre-ageing can improve the paint-bake response of the 6xxx alloys, pre-ageing was found to reduce their stretch formability due to the decreased work hardening and strain rate hardening capabilities. This effect is especially pronounced in the case when the samples are pre-aged at 100 oC for 2 h, as pre-ageing reduces the strain rate hardening appreciably. Therefore, this work suggests that any attempts at improving the stretch formability of 6xxx alloys must also consider their effects on the paint-bake response.Finally, thermodynamic modelling results show that the stretch formability of the excess Mg alloy A2, which has a relatively poor stretch formability, can be improved by increasing the Si and Mn contents and/or decreasing the Mg content.Thus, a tangible outcome of the PhD project is a detailed set of reliable experimental results on the effect of the alloy composition and heat treatment of 6xxx alloys studied on their strength and ductility characteristics, stretch formability, and bake-hardening response. Moreover, practically, this PhD project not only explains why most of the commercial 6xxx alloys for automotive outer panels are Si-rich alloys, but also provides guidance for the development of Mg-rich 6xxx alloys for automotive panel applications.

Download or read book The Deformation Characteristics and Microstructural Dynamics of an AL 10MG 0 1ZR Alloy written by and published by . This book was released on 1992 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: An investigation into microstructural evolution during processing and superplastic deformation of an Al-10Mg-0.1Zr alloy was conducted. Processing schedules were modified to enhance particle-stimulated nucleation of recrystallization and refine subsequent gain size. Strain rates varying over three orders of magnitude were utilized in subsequent testing of processed material. At lower strain rates of about 10-4 sec-1 coarsening of the microstructure was apparent and elongations of 277% were obtained. A strain rate of 10-3 sec-1 resulted in lesser coarsening and elongations of 650%. A model of deformation by grain boundary sliding in association with microstructural coarsening is presented.

Download or read book Dependence of Microstructure Evolution Texture and Mechanical Behavior of a Magnesium Alloy on Thermo mechanical Input During Friction Stir Processing written by Zhenzhen Yu and published by . This book was released on 2010 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the relationship among friction stir processing (FSP) parameters, microstructure evolution, texture development, and mechanical hehavior[sic] of AZ31B Mg alloy was investigated. First of all, in order to reveal the correlation among the deformation conditions, dynamic recrystallization (DRX) mechanisms, and microstructure evolution in the Mg alloy, hot compression tests at a wide range of Zener-Hollomon parameter (Z) values were conducted. Through optical microscopic examination, it was found out that above a critical Z value, twinning influences the DRX process resulting in a more effective grain refinement, which is manifested in a significant change in the slope of the Z-d[subscript rec] relationship, where d[subscript rec] is the recrystallized grain size. Moreover, EBSD examination revealed that the twinning also contributed to a distinct change in the recrystallization texture. Compression tests were performed along both through-thickness and in-rolling-plane directions of the plate to study the orientation dependency of twinning activities and its influence on the DRX process. X-ray line profile analysis (XLPA) provides further insights by highlighting the differences in the dislocation density/types, subgrain sizes, and twin densities during the DRX processes operating with or without the twinning. Secondly, the constitutive behaviour study was applied to the investigation of microstructure evolution during FSP. By varying the key FSP parameters systematically, i.e. rotation and travel rates of the tool, a series of FSP specimens were prepared with a wide range of thermo-mechanical inputs in terms of Z. The resulting tensile behavior in the stir zone (SZ) showed a dramatic change as a function of Z, caused by a systematic change in the texture within SZ measured by neutron diffraction. A three-dimensional transient model was developed to investigate the detailed deformation history including the temperature and strain rate profiles and material flow pattern during FSP of the Mg alloy. Such deformation history can be combined with the constitutive study from the compression tests in order to analyze the developments of micro-texture and DRX grains during FSP, which will, in turn, dominate the mechanical properties. Based on the studies above, new fundamental understandings were gained on the governing mechanisms for the deformation and recrystallization processes during FSP and the influence of thermo-mechanical input during FSP on ductility enhancement in the Mg alloy.

Download or read book Microstructural Evolution During Aging of an Al Cu Li Ag Mg Zr Alloy written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-20 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: Alloys in the Al-Cu-Li Ag-Mg subsystem were developed that exhibit desirable combinations of strength and ductility. These Weldalite (trademark) alloys, are unique for Al-Cu-Li alloys in that with or without a prior cold stretching operation, they obtain excellent strength-ductility combinations upon natural and artificial aging. This is significant because it enables complex, near-net shape products such as forgings and super plastically formed parts to be heat treated to ultra-high strengths. On the other hand, commercial extrusions, rolled plates and sheets of other Al-Cu-Li alloys are typically subjected to a cold stretching operation before artificial aging to the highest strength tempers to introduce dislocations that provide low-energy nucleation sites for strengthening precipitates such as the T(sub 1) phase. The variation in yield strength (YS) with Li content in the near-peak aged condition for these Weldalite (trademark) alloys and the associated microstructures were examined, and the results are discussed. Kumar, K. S. and Brown, S. A. and Pickens, Joseph R. Unspecified Center ...

Download or read book Mechanical and Microstructural Characteristics of an Al Li Cu Zr Alloy During Superplastic Deformation written by Binyan Ren and published by . This book was released on 1991 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: