Papers by Keyword: Al-Mg

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Authors: S. Sarkar, Mary A. Wells, Warren J. Poole
Abstract: An investigation was conducted on the softening behaviour of cold rolled continuous cast (CC) AA5754 Al alloy and compared to the results for the ingot cast (IC) material. The present study suggests that the CC material exhibits greater resistance to softening as compared to the IC AA5754 for the same amount of cold deformation. The differences in the softening kinetics become more noticeable with increasing level of cold deformation and from a processing point of view can be attributed to the absence of the homogenization stage during the processing of the CC material. Resistivity measurements were carried out during the annealing treatment of the CC materials to examine the possibility of concurrent precipitation, which could potentially retard the softening kinetics for these materials. In addition, the current research reveals that the CC material produces a finer recrystallized grain size as compared to the IC material.
1641
Authors: Jürgen Hirsch
33
Authors: M. Lopez-Pedrosa, Bradley P. Wynne, Mark W. Rainforth
Abstract: The effects of strain path reversal on the microstructure in AA5052 have been studied using high resolution EBSD. Deformation was carried out using two equal steps of forward/forward (F/F) or forward/reverse (F/R) torsion at a temperature of 300°C and strain rate of 1s-1 to a total strain of 0.5. In both cases the deformation microstructure in the majority of grains analysed consisted of microband arrays clustering at specific angles to the macroscopic deformation axes. For the F/F condition microbands clustered around -20° and +45° to the maximum principle stress direction, whilst for the F/R condition significantly more spread in microband angle was observed. This suggests that the microbands formed in the forward deformation have or are dissolving and any new microbands formed are related to the deformation conditions of the final strain path. This leads to the conclusion that instantaneous deformation mode determines the orientation of new microbands formed whilst a non-linear strain path history influences the range of misorientation angle in the material through the dissociation of previously formed microbands and the formation of new microbands at the new straining condition, leading to a lower level of misorientation angle. Analysis of material subjected to static annealing at 400°C for 1 hour appears to correspond with these observations as the F/F material was completely recrystallised with a fine grain structure whilst the F/R material had no major signs of recrystallisation.
223
Authors: Bradley P. Wynne, O. Hernandez-Silva, M. Lopez-Pedrosa, Mark W. Rainforth
Abstract: The effects of strain path reversal, using forward and reverse torsion, on the microstructure evolution in the aluminium alloy AA5052 have been studied using high resolution electron backscatter diffraction. Deformation was carried using two equal steps of forward/forward or forward/reverse torsion at a temperature of 300°C and strain rate of 1s-1 to a total equivalent tensile strain of 0.5. Sections of the as-deformed gauge lengths of both test specimens were then annealed at 400°C for 1 hour in a salt bath in order to investigate their subsequent recrystallisation response. In both strain path histories the deformation substructure in the grains analysed consisted of microband arrays within an equiaxed dislocation cell structure. The material subjected to forward/forward deformation did, however, have a slightly greater number of low angle boundaries, i.e. boundaries < 15° misorientation, whilst the forward/reverse material had some grains containing little evidence of substructure. On annealing both materials had significantly reduced levels of low angle boundaries but only the forward/forward material had an increased number of high angle boundaries and a reduced grain size, indicating recrystallisation had only occurred in this material. This would suggest that the deformation microstructure within the forward/forward condition was sufficient to initiate and maintain recrystallisation whilst the microstructure produced by the forward/reverse test contained insufficient nuclei or internal energy to produce a recrystallised material within 1 hour. Further work is now required at different annealing times in order to determine if the major effect of strain path is on retarding nucleation, growth or both.
407
Authors: Geoff M. Scamans, Andreas Afseth, George E. Thompson, Y. Liu, Xiao Rong Zhou
Abstract: Over the past ten years a detailed understanding of the dominant factors controlling the corrosion susceptibility of painted aluminium alloy sheet used for architectural and automotive applications has been developed. Work carried out in this field will be reviewed and the different modes of cosmetic corrosion that can occur-, the mechanisms of surface activation, and the role of different thermo-mechanical processing steps on controlling corrosion susceptibility for different alloy systems, including Al-Mn, Al-Mg and Al-Mg- Si-(Cu) will be discussed. The critical role of chemical or electro-chemical cleaning prior to pre-treatment and coating will be highlighted and prospects for meaningful accelerated testing will be discussed.
647
Authors: Zeng Tao Chen, Michael J. Worswick, David J. Lloyd
Abstract: The numerical simulation of the stretch flange forming operation of Al-Mg sheet AA5182 was conducted with an explicit finite element code, LS-DYNA. A Gurson-Tvergaard- Needleman (GTN)-based material model was used in the finite element calculation. A strain controlled void nucleation rule was adopted with void nucleating particle fraction measured directly from the as-received Al-Mg sheet. Parametric study was performed to examine the effect of void nucleation strain on the predicted onset of ductile fracture. Critical porosity levels determined through quantitative metallurgical analysis were adopted to predict the commencement of void coalescence in the GTN model. The numerical results were compared to the experimental ones and an applicable void nucleation strain was suggested.
815
Authors: Miroslav Cieslar, P. Vostrý, Ivana Stulíková
1049
Authors: Suk Bong Kang, Jae Woon Kim, Hyoung Wook Kim
Abstract: Recently the method for obtaining ultra-fine grained metallic materials has developed using severe plastic deformation (SPD), such as equal channel angular pressing (ECAP), accumulative roll bonding (ARB), torsion straining, and warm multiple deformation (WMD) etc. In order to enhance thermal stability of ultra-fine grained aluminum alloys manufactured by SPD process, the addition of Sc and Zr elements has been considered to devise fine Al3Sc, Al3Zr and Al3(Scx Zr1-x) precipitates for inhibiting the grain growth. In this study, the microstructure evolution has been investigated in Al-Mg alloys with and without Sc and Zr addition during the warm multiple deformation process. In addition Al-Mg alloys were compressed at a strain rate of 10-1 sec-1 by two different routes, that is, route A and route B. Route A is to rotate the specimen throughout 90o around the vertical axis of loading direction at every pass. Route B is to rotate the specimen throughout 90o around the parallel axis of loading direction and then rotate it again as route A. The specimen deformed by route B had finer grain size and more uniform distribution of grains than those deformed by route A. When the warm multiple deformation process repeated up to 8 passes at 673 K, the specimen consisted of ultra-fine grained structure with the average grain size less than 3 μm. The superplastic behavior can also be observed at the high strain rate and low temperature regime.
847
Authors: Hidetoshi Umeda, Goroh Itoh, Yoshinori Kato
Abstract: The effect of heat treatment conditions such as atmosphere, temperature, annealing time and alloying elements on the hydrogen content in Al-Mg based alloys was investigated. The hydrogen content after annealing depends on the annealing atmospheres and alloying elements. When annealed in a wet atmosphere, the release of the hydrogen in the Al-Mg alloys to outside and the absorption of hydrogen from atmosphere into Al-Mg alloys are presumed to occur at the same time. The oxide layer on the surface is revealed to prevent the hydrogen from being released to outside. The spheroidal MgO particles can be seen on the surface of Al-Mg alloys after annealing at 550°C. The number of the MgO particles increases with increasing impurity elements such as Si and Fe, reducing the shielding effect against hydrogen permeration. Therefore, the condensation of hydrogen near the surface after annealing occurs more easily in an Al-Mg alloy of a high-purity than that of an ordinary purity.
1895
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