Modelling of uniaxially pre-strained and annealed AZ31 magnesium sheet based on microstructural considerations

Material deformation at room temperature and subsequent thermal aspects are analyzed at the microstructural level to understand the uniaxial deformation behavior of AZ31 magnesium sheet from pre-straining and annealing (PSA) process. The sheet is pre-strained in uniaxial tension to various strains by conducting interrupted tests and its uniaxial stress-strain responses are obtained. The pre-strained specimens are then annealed at different temperatures and times and then reloaded in uniaxial tension to obtain their post-anneal stress-strain response up to large strains. Pre and post-annealing mechanical responses are analyzed and correlated with static recovery, grain recrystallization and growth kinetics from annealing. Experimental results are utilized to develop and validate a microstructure-based model to capture the room temperature mechanical and grain-level responses of AZ31 sheet from the PSA process. The model incorporates the effect of recovery on the recrystallization kinetics, as well as non-constant nucleation and growth behavior in order to predict the grain size at the end of recrystallization and within the grain growth stage. In addition, the mechanical properties of PSA materials are predicted by considering the resulting microstructure as a composite of un-recrystallized, recrystallized and coarsened grain regions and by employing the rule of mixture.