Abstract The present work, for the first time, quantitatively studies the evolution of both dislocations and deformation twins with various strain rates in an ATZ311 Mg alloy. Interrupted tensile tests were performed at the strain rates of 0.001, 1 and 600 s−1. Deformation twins were characterized by microscopy techniques and evaluated using the fractions of twin boundaries and twinned area. The average dislocation density and the relative fractions of dislocations with different Burgers vectors were determined from neutron diffraction data. It was found that the twin fraction increases remarkably and becomes saturated at lower strain rates (0.001-1 s−1), while the dislocation density only obtains an obvious enhancement at a much higher strain rate (600 s−1). Besides, the distinctively high flow stress at high strain rate leads to a substantial increase in the density of the hard-to-activate 〈 c + a 〉 -type dislocations, after the 〈 a 〉 -type dislocation density reaches rapidly its saturated value at a small strain level. The twinning modes with opposite polarities are able to coexist in the same grains because of the high local stress concentration at strain rates above 1 s−1.

中文翻译：

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准静态和高应变率下镁合金中位错和孪晶密度的演变

摘要 本工作首次定量研究了ATZ311 镁合金中不同应变速率下位错和变形孪晶的演化。断续拉伸试验在 0.001、1 和 600 s-1 的应变速率下进行。变形孪晶通过显微技术表征，并使用孪晶边界和孪晶面积的分数进行评估。平均位错密度和不同 Burgers 向量的位错相对分数由中子衍射数据确定。发现孪晶分数显着增加并在较低应变速率（0.001-1 s-1）下饱和，而位错密度仅在更高的应变速率（600 s-1）下获得明显增强。除了，在高应变速率下显着的高流动应力导致难以激活的 〈 c + a 〉 型位错的密度显着增加，在 〈 a 〉 型位错密度以较小的速度迅速达到其饱和值之后应变水平。由于应变速率高于 1 s-1 时的局部应力集中，具有相反极性的孪晶模式能够共存于同一晶粒中。