LPSO相对超轻Mg-Li合金热变形行为的影响

Effect of LPSO phase on hot deformation behavior of ultra-light Mg-Li alloy

采用Gleeble-3500热模拟机在250~400℃、应变速率为10^(-3)~1 s^(-1)的条件下,研究了不同变形温度和应变速率对Mg-5Li-11Gd-1Zn-0.5Zr合金高温流变应力和显微组织的影响,根据Arrhenius模型建立了本构方程,根据动态材料模型理论(DMM)建立了热加工图,得到了最佳热加工参数。结果表明:合金的稳态流变应力随着变形温度的增加而减小,随着应变速率的增加而增加。随着变形温度的增加,长周期堆垛有序(LPSO)相发生扭折或者细化,合金的动态再结晶程度逐渐增加;随着应变速率的增加,LPSO相分布更加均匀,合金的晶粒尺寸逐渐增加。通过计算,合金的热变形激活能为142.65 kJ/mol,由热加工图得出本合金热加工的失稳区及安全区,其易加工区域变形温度和应变速率分别为350~400℃、0.011~0.45 s^(-1),在此区域内颗粒状分布的LPSO相可促进动态再结晶的发生。

Effects of deformation temperature and strain rate on the high temperature flow stress and microstructure of the Mg-5Li-11Gd-1Zn-0.5Zr alloy were studied by using Gleeble-3500 thermal simulator at 250-400℃ and strain rate of 10^(-3)-1 s^(-1).The results show that the steady-state flow stress of the alloy decreases with the increase of deformation temperature and increases with the increase of strain rate.With the increase of deformation temperature,the long period stacking ordered(LPSO)phase kinks or refines,and the degree of dynamic recrystallization of the alloy increases gradually.With the increase of strain rate,the LPSO phase distribution is more uniform and the grain size of the alloy increases gradually.The thermal deformation activation energy calculated according to the Arrhenius theory is 142.65 kJ/mol.The instability area and safe area are obtained from the hot processing map,the easy processing area of the alloy is in the range of the deformation temperature of 350-400℃and strain rate of 0.011-0.45 s,where the granular LPSO phase can promote dynamic recrystallization.