晶粒尺寸、变形温度和应变率对Mg-12Gd-3Y-0.5Zr合金力学性能的影响

通过对Mg-12Gd-3Y-0.5Zr合金进行单向拉伸试验,检验晶粒尺寸、温度和应变率对合金力学性能的影响。通过退火处理可以获得不同晶粒尺寸((9.63±0.69)～(94.24±2.41)μm)的试样,拉伸温度分别为20℃、-25℃和-50℃。当温度足够低时,塑性变形由滑移主导的变形方式向孪生主导过渡;同样的情况可在晶粒尺寸变大时发生。变形机制的转变导致Hall-Petch关系中斜率的变化。采用Zener-Hollomon参量来描述温度、应变率对孪生的综合影响。实验结果表明,随着Z参量的变大,孪生发生率增大;当Z值足够大时,变形机制发生转变。

Effect of Grain Size, Temperature and Strain Rate on Deformation Twinning of Mg-12Gd-3Y-0.5Zr Alloy

The effect of grain size,temperature and strain rate on the mechanical property of extruded Mg-12Gd-3Y-0.5Zr alloy tested in tension condition was examined.Samples with grain sizes varying between(9.63±0.69) to(94.24±2.41)μm were prepared by altering the time of annealing.Tension testing of the samples was carried out at temperature among 20℃,-25℃ and-50℃.Slip dominated the deformation at high temperature but it gave way to twinning dominated flow when the temperature was lowered.A similar transition was observed when the grain size was increased or the strain rate was raised.The transition was accompanied by a change in Hall-Petch slope.Combined effect of temperature and strain rate on twinning was analyzed by using Zener-Hollomon parameter Z,and it was found that the larger Z led to bigger area fraction of twinning lamellae,and the mechanism of deformation varied when Z was large enough.