粉末冶金Mo–14Re合金热变形行为及微观组织演变

Thermal deformation behavior and microstructure evolution of Mo-14Re alloys prepared by powder metallurgy

通过Gleeble 1500热模拟试验机对粉末冶金法制备的Mo–14Re合金进行了恒应变速率压缩实验,分析了变形温度(1100~1400℃)和应变速率(0.100~0.001 s-1)对流变应力及组织演变的影响,并采用双曲正弦型Arrhenius模型建立了Mo–14Re合金的本构方程。结果表明:随着变形温度升高或者应变速率降低,粉末冶金Mo–14Re合金在热变形过程的流变应力也随之减小,真应力–真应变曲线表现出明显的加工硬化和动态软化现象。动态软化行为主要归结于粉末冶金Mo–14Re合金热压缩变形处于低应变速率(0.010 s-1和0.001 s-1)或较高变形温度(>1200℃)时发生的动态再结晶,形核方式为晶界凸出形核,随着应变速率的降低或温度的升高,再结晶程度不断增加,晶粒不断长大,当温度为1400℃,应变速率为0.001 s-1时,完全再结晶完成。

The constant strain rate compression experiment of powder metallurgy Mo–14Re alloys was carried out by Gleeble 1500 thermal simulation tester.The effects of deformation temperature(1100~1400℃)and strain rate(0.100~0.001 s-1)on the flow stress and microstructure evolution were analyzed.The constitutive equation of Mo–14Re alloys was established by hyperbolic sinusoidal Arrhenius model.The results show that,the flow stress of powder metallurgy Mo–14Re alloys decreases with the increase of deformation temperature or the decrease of strain rate during the thermal deformation,and the true stress-true strain curve shows the obvious work hardening and dynamic softening phenomenon.The dynamic softening behavior is mainly attributed to the dynamic recrystallization of Mo–14Re alloys at low strain rate(0.010 s-1 and 0.001 s-1)or high deformation temperature(>1200℃)during the thermal compression.The nucleation mode is grain boundary protruding nucleation.With the decrease of strain rate or the increase of temperature,the degree of recrystallization continues to increase,the grains continue to grow,and the Mo–14Re alloys are completely recrystallized at 1400℃with the strain rate of 0.001 s-1.