高應(yīng)變速率軋制ZK60板材的超塑性行為Superplasticity behavior of ZK60 alloy sheet prepared by high strain rate rolling process

研究高應(yīng)變速率軋制ZK60鎂合金板材在523~673 K、1×10^-3~1×10^-1 s^-1初始應(yīng)變速率下的超塑變形行為及其特征。研究發(fā)現(xiàn)：軋制態(tài)ZK60板材在648 K、1×10^-3 s^-1拉伸時(shí)，可獲得最大伸長(zhǎng)率650%，應(yīng)變速率敏感性指數(shù)高達(dá)0.53；在623 K、1×10^-2 s^-1拉伸時(shí)，可獲得伸長(zhǎng)率584.5%，應(yīng)變速率敏感性指數(shù)為0.47，呈現(xiàn)出較好的高應(yīng)變速率超塑性。微觀組織與理論分析表明：ZK60合金板材在高應(yīng)變速率下的超塑性變形過(guò)程中主要的變形機(jī)制為晶界滑移機(jī)制(GBS)，主要協(xié)調(diào)機(jī)制為晶界擴(kuò)散控制的位錯(cuò)蠕變，同時(shí)還伴有一定程度的液相輔助協(xié)調(diào)機(jī)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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