高应变速率轧制ZK60板材的超塑性行为Superplasticity behavior of ZK60 alloy sheet prepared by high strain rate rolling process

研究高应变速率轧制ZK60镁合金板材在523~673 K、1×10^-3~1×10^-1 s^-1初始应变速率下的超塑变形行为及其特征。研究发现：轧制态ZK60板材在648 K、1×10^-3 s^-1拉伸时，可获得最大伸长率650%，应变速率敏感性指数高达0.53；在623 K、1×10^-2 s^-1拉伸时，可获得伸长率584.5%，应变速率敏感性指数为0.47，呈现出较好的高应变速率超塑性。微观组织与理论分析表明：ZK60合金板材在高应变速率下的超塑性变形过程中主要的变形机制为晶界滑移机制(GBS)，主要协调机制为晶界扩散控制的位错蠕变，同时还伴有一定程度的液相辅助协调机制。

The superplastic deformation characteristics of the high strain rate rolling ZK60 magnesium alloys at temperature ranging from 523 K to 673 K and at an initial strain rates ranging from 1×10^-3 s^-1 to 1×10^-1 s^-1 were investigated. The results show that the maximum elongation to failure of 650% is obtained at 648 K and the strain rate of 1×10^-3 s^{-1 in the as-rolled ZK60 magnesium alloys and its strain rate sensitivity (m) is high up to 0.53. An excellent high strain rate superplasticity with the elongation to failure of 584.5% is obtained at 623 K and the strain rate of 1}×10^-2 s^-1 and its strain rate sensitivity (m) is 0.47. The microstructure and theoretical analysis shows that, at temperature above 573 K, the dominant deformation mechanism in high strain rate superplasticity is grain boundary sliding (GBS), which was studied systematically. The dislocation creep controlled by grain boundary diffusion was considered the main accommodation mechanism, and high strain rate superplasticity was also accompanied by a certain degree of inter-granular liquid phase aiding mechanism, which was observed.

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