The dynamic mechanical response and deformation mechanism of magnesium-yttrium alloy at high strain rate were investigated using split-Hopkinson pressure bar (SHPB) impact, and the microstructure evolution and crack formation mechanism were revealed. The yield strength and work hardening rate increase significantly with increasing impact strain rate. Deformation twinning and non-basal dislocation slip are the primary deformation mechanisms during testing. Contrary to crack initiation mechanism facilitated by adiabatic shear bands, we find that high-density co-axial nanocrystalline grains form near cracks, which leads to local softening and promotes crack initiation and rapid propagation. Most grains have similar $〈\overline{1}2\overline{1}0〉$$〈\overline{1}2\overline{1}0〉$ orientations, with unique misorientation of 24°, 32°, 62°, 78° and 90° between adjacent grains, suggesting that these grains are primarily formed by interface transformation, which exhibits distinct differences from recrystallized grains. Our results shed light upon the dynamic mechanical response and crack formation mechanism in magnesium alloys under impact deformation.

中文翻译：

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动态机械响应和变形诱导的同轴纳米晶粒促进了镁钇合金裂纹的形成


采用分体式霍普金森压杆 （SHPB） 冲击研究了镁钇合金在高应变速率下的动态力学响应和变形机制，揭示了其微观组织演变和裂纹形成机制。屈服强度和加工硬化率随着冲击应变率的增加而显著提高。变形孪生和非基底位错滑移是测试过程中的主要变形机制。与绝热剪切带促进的裂纹萌生机制相反，我们发现在裂纹附近形成高密度同轴纳米晶粒，这导致局部软化并促进裂纹萌生和快速扩展。大多数谷物具有相似的 $〈\bar{1}2\bar{1}0〉$取向，相邻晶粒之间具有 24°、32°、62°、78° 和 90° 的独特取向差，表明这些晶粒主要由界面转变形成，这与再结晶晶粒表现出明显的差异。我们的结果揭示了镁合金在冲击变形下的动态机械响应和裂纹形成机制。