An AZ91 magnesium alloy (Mg-9%, Al-1% Zn) was processed by high-pressure torsion (HPT) after solution-heat treatment. Tensile tests were carried out at 423, 523, and 623 K in the strain rate range of 10⁻⁵−10⁻¹ s⁻¹ to evaluate the occurrence of superplasticity. Results showed that HPT processing refined the grain structure in the alloy, and grain sizes smaller than 10 µm were retained up to 623 K. Superplastic elongations were observed at low strain rates at 423 K and at all strain rates at 523 K. An examination of the experiment data showed good agreement with the theoretical prediction for grain-boundary sliding, the rate-controlling mechanism for superplasticity. Elongations in the range of 300–400% were observed at 623 K, attributed to a combination of grain-boundary-sliding and dislocation-climb mechanisms.

中文翻译：

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使用高压扭力在AZ91镁合金中实现超塑性

固溶热处理后，通过高压扭转（HPT）处理AZ91镁合金（Mg-9％，Al-1％Zn）。在423、523和623 K的应变速率范围为10 ^-5 -10 ^-1 s ^-1的条件下进行了拉伸试验评估超塑性的发生。结果表明，HPT处理可细化合金中的晶粒结构，并在623 K以下保留小于10 µm的晶粒尺寸。在423 K的低应变速率和523 K的所有应变速率下均观察到超塑性伸长。实验数据与晶界滑动的理论预测和超塑性的速率控制机制相吻合。在623 K处观察到300-400％的延伸率，这归因于晶界滑动和位错爬升机制的结合。