The deformation behavior of Mg-2Zn-0.1Ca alloy sheet: The role of strain rate

Ductility in materials often exhibits a strong dependence on strain rate, governed by underlying deformation mechanisms and strain heterogeneity. This study explores the deformation behavior of a Mg-2Zn-0.1Ca alloy sheet under two strain rates (1 × 10⁻⁵ s⁻¹ and 1 × 10⁻¹ s⁻¹). High-resolution digital image correlation measurements revealed significant strain heterogeneities, even in early stage of tension (ε = 2 %). Contrary to expectations, higher strain rates did not amplify these heterogeneities. Slip trace analysis demonstrated a transition in deformation modes at both strain rates: basal slip (ε = 2 %) → basal slip + non-basal slip + twinning (ε = 7 %). Notably, the sample tested at the higher strain rate exhibited higher activity of prismatic and pyramidal slip systems. The high-strain-rate tested sample exhibited enhanced activity in prismatic and pyramidal slip systems. A higher density of non-basal dislocations in the high-strain-rate sample was detected, potentially enhancing stress concentration and initiating premature cracking. Moreover, evaluation of the geometric compatibility factor for basal slip indicated reduced slip transferability at higher strain rates. The combined effects of reduced slip transferability and increased non-basal dislocation density is identified as a key factor in the reduced ductility observed at high strain rates.