Mo-14Re钼铼合金高温压缩耦合内变量的本构模型建立

High Temperature Compression Tests of Molybdenum-Rhenium Alloys and Constitutive Model Establishment with Internal State Variables

为研究Mo-14Re钼铼合金高温流变行为及其跨尺度表征,采用Gleeble热模拟试验机对钼铼合金棒材进行了高温压缩试验,选取的温度为1400、1500、1600℃,应变速率为0.01、0.1、1、10 s^(-1)。结果表明,高温和低应变率变形时,应变率敏感因子逐渐增大,材料塑性流动性能也就越好,且变形过程中应力硬化和软化2种现象同时存在。在此基础上,建立了跨尺度本构模型,流变应力表征考虑了与不动位错的阻力、热激活、晶界效应的微观剪切应力,微观组织演变考虑了晶粒尺寸、位错密度、动态再结晶率以及裂纹体积分数等微观组织演变。随后基于遗传算法确定了模型中的材料参数,屈服应力、晶粒尺寸和流变应力的模型计算值与试验结果吻合,可知该模型可以描述Mo-14Re钼铼合金在高温变形时流变行为及其微观组织演变。

The flow behavior of Mo-14Re molybdenum-rhenium alloy at high temperature and its cross-scale characterization were investigated through high temperature compression test of the alloy bar which was carried out by Gleeble thermal simulation testing machine at the selected temperature of 1400,1500 and 1600℃and the strain rate of 0.01,0.1,1 and 10 s^(-1).The results show that when the alloy is deformed at high temperature and low strain,the strain rate sensitivity factor increases gradually,and the plastic flow performance of the material becomes better;in the meantime,the two phenomena of stress hardening and softening exist simultaneously during deformation.On this basis,a cross-scale constitutive model was established.The flow stress characterization takes into account the resistance,thermal activation and the immobile dislocation of grain boundary effects.The microstructure evolution takes into account the grain size,dislocation density,dynamic recrystallization rate and crack volume fraction.The calculated values of yield stress,grain size and flow stress are in good agreement with the experimental results.It can be seen that the model can describe the rheological behavior and microstructure evolution of Mo-14Re molybdenum-rhenium alloy during high temperature deformation.