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.

中文翻译：

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Mg-2Zn-0.1Ca 合金板的变形行为：应变率的作用


材料的延展性通常表现出对应变率的强烈依赖性，而应变率受潜在的变形机制和应变异质性控制。本研究探讨了 Mg-2Zn-0.1Ca 合金板在两种应变速率 （1 × 10⁻⁵ s⁻¹ 和 1 × 10⁻¹ s⁻¹）下的变形行为。高分辨率数字图像相关测量揭示了显着的应变异质性，即使在张力的早期阶段 （ε = 2 %）。与预期相反，较高的应变率并没有放大这些异质性。滑移轨迹分析表明，在两种应变速率下，变形模式均存在过渡：基底滑移 （ε = 2 %） → 基底滑移 + 非基底滑移 + 孪晶 （ε = 7 %）。值得注意的是，在较高应变速率下测试的样品表现出较高的棱柱形和金字塔形滑移系统的活性。高应变率测试样品在棱柱形和金字塔形滑移系统中表现出增强的活性。在高应变率样品中检测到更高密度的非基底位错，这可能会增强应力集中并引发过早开裂。此外，对基底滑移的几何相容因子的评估表明，在较高应变速率下滑移性降低。减少滑移性和增加非基底位错密度的综合效应被认为是在高应变速率下观察到的延展性降低的关键因素。