An efficient temperature-dependent crystal plasticity framework for pure magnesium with emphasis on the competition between slip and twinning

Abstract

Experimental evidence suggests that the formation of compressive twin bands and the associated strain localization is a key driver behind the low ductility of magnesium (Mg) at ambient temperature, which is why processing is often performed at elevated temperature. Modeling Mg and its alloys across the temperature range of interest is challenging and must account for the experimentally reported competition between compressive twins and pyramidal slip. Unfortunately, only few temperature-aware models for pure Mg and Mg alloys exist and many either disregard compressive twins entirely or suffer from efficiency or calibration issues, while experimental evidence of the active deformation modes has remained inconclusive. To describe the temperature-dependent behavior we introduce a new efficient, temperature-aware crystal-plasticity framework for pure Mg. Experimental stress–strain and texture data are used to calibrate the model over the range from room temperature to 300 ◦C. The calibrated model predicts single- and polycrystal stress–strain responses accurately in comparison with experimental data. By comparing two versions of the model – with and without compressive twins – we highlight their impact on the microstructure and texture evolution. Results highlight a transition in deformation modes from compressive twins at low temperature to pyramidal II slip at elevated temperature, confirming that the temperature dependence of pure Mg is primarily governed by non-basal slip. We thus provide an accurate and efficient modeling tool for the temperature-dependent mechanical behavior of pure Mg, while also shedding light onto the relative importance of non-basal slip vs. compressive twins as a function of temperature.