UBC Theses and Dissertations
The deformation behaviour of a Mg-8Al-0.5Zn alloy Jain, Jayant
In this work, the deformation behaviour of an Mg-8Al-0.5Zn (AZ80) alloy having a fixed initial grain size of ~ 32 µm was studied by varying the initial texture, temperature, stress state and microstructure. The work focused on investigating the influence of these variables on the mechanical properties, work hardening characteristics, texture evolution and deformation mechanisms of the alloy. The initial materials with different starting textures (i.e. strongly and weakly textured) and microstructures (i.e. solution-treated and aged) were obtained through a series of thermo-mechanical treatments including cold rolling, annealing and ageing. The uniaxial compression and tension deformation experiments were carried out on strongly and weakly textured solution-treated and aged samples at 77K and 293K. Neutron diffraction, slip trace analysis, high and low resolution EBSD were used to characterize the texture evolution and deformation mechanisms of the alloy. In addition, a visco-plastic self consistent (VPSC) model was used to predict the influence of initial texture and temperature on the deformation behaviour. The results show that temperature and loading direction with respect to initial texture has a pronounced effect on yield strength and work hardening. It is found that there is a substantial difference between the nature of twinning, slip system activity and texture development as a function of deformation temperature. It is shown that the VPSC model is effective in predicting the deformation response of alloy when it is dominated by slip. The same model however proved to be inadequate for twinning dominated deformation. The results illustrate that precipitates are capable of changing the balance of deformation mechanisms and texture development of the alloy. They were found to be extremely effective in reducing the well known tension compression yield asymmetry exhibited by magnesium and its alloys.
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