UBC Theses and Dissertations
Mechanical properties of a recovered Al-Mg-Sc alloy Roumina, Reza
In this study the effect of recovery on the yield strength and work hardening of a model Al-Mg-Sc alloy in the presence of A1₃Sc precipitates was investigated. Recovered microstructures containing A1₃Sc precipitates were obtained through a series of thermo-mechanical treatments including pre-aging, cold rolling and annealing. Recovered microstructures were characterized in terms of precipitate size distribution, subgrain sizes and dislocation structures. Yield strength and work hardening of processed microstructures were examined by tensile testing at 77K. The results show that the effect of precipitates arises directly from precipitation strengthening as well as indirectly from their effectiveness at controlling the recovered microstructure. Physical based models were developed to describe the tensile response of recovered microstructures consistent with previous models on single phase recovered Al-Mg alloys. For the first time, the impact of precipitates on recovery kinetics was captured by coupling recovery models of single phase Al-Mg alloys and creep models. In this new modelling approach a transition stage from dislocation annihilation to a climb controlled mechanism was defined. In addition, the effects of both recovery and precipitates on work hardening have been incorporated in the previous models. Finally, model limitations as well as their potential applications to improve mechanical properties including yield strength, ultimate tensile strength and uniform elongation of Al-Mg-Sc alloys by controlling thermo-mechanical processing and chemical composition were revisited.
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