基于实验与计算的Fe微合金化Ti-6Al-4V热变形行为研究（英文）

Hot Deformation Behavior of Fe-microalloyed Ti-6Al-4V Based on Experiments and Calculations

对Ti-6Al-4V-0.35Fe合金的热变形行为进行了系统的研究。采用Gleeble3800热/力模拟试验机研究了热加工参数与流变应力之间的关系,其温度范围与应变速率范围分别为800~950℃与0.001~10 s^-1。流变曲线的单峰分布表明,动态再结晶机制在变形过程中占主导地位。TEM分析表明,动态再结晶晶粒尺寸随变形温度的改变而改变,且在较低温度下由于动态球化形成了尺寸较小的晶粒。由于位错的滑移和攀移,亚晶界中形成了位错胞壁。运用Avrami动态再结晶模型与应力补偿多变量回归模型对热变形过程中的应力应变实验数据进行了修正。为了描述其流变行为,对这2种类型的本构模型进行了对比研究。实验表明,这2种模型对预测Ti-6Al-4V-0.35Fe合金的流变应力都具有良好的准确性。为了判断热加工的稳态加工区域与失稳加工区域,建立了一个应变量为0.8,基于动态材料模型的热加工图。与Ti-6Al-4V钛合金相比,稳态加工的应变速率范围由0.0003~0.1 s-1扩大到0.001~0.6 s^-1。最优的热加工参数为920~950℃与0.001~0.6s^-1,在此过程中几乎完全发生了动态再结晶。结果表明,在800~950℃的条件下,Fe微合金化的Ti-6Al-4V热加工性能优于Ti-6Al-4V合金,且加工成本较Ti-6Al-4V低。

Hot deformation behaviors of Ti-6 Al-4 V-0.35 Fe were studied,which is significant to improve plastic deformation ability of titanium alloys.In experiment,we used a Gleeble 3800 thermo-mechanical simulator to obtain the relationship between thermomechanical parameters and flow stress in a range of temperatures(800~950℃)and strain rates(0.001~10 s^-1).The single-peak profiles of the flow curves indicate that dynamic recrystallization(DRX)mechanism dominates the deformation.TEM analysis indicates that the grain size in DRX changes under different deformation temperatures,and finer grains are formed at relatively lower temperature due to the dynamic globularization.The dislocation walls are formed in subgrain boundaries due to dislocation slipping-climbing.The Avrami-type DRX model and the strain compensated multivariable regression model were applied to fit the experimental stress-strain data during hot deformation.A comparative study between these two types of constitutive models was conducted to represent the flow behavior.It is found that both models have good accuracy in predicting the flow stress of Ti-6 Al-4 V-0.35 Fe alloy.A processing map based on dynamic material model(DMM)at the strain of 0.8(steady-state flow stage)was established to identify the flow instability regions and stability regions.The strain rate range of stability region is 0.001~0.6 s^-1 which has been expanded compared to the range of 0.0003~0.1 s^-1 of Ti-6 Al-4 V.Optimal hot working parameters are confirmed to be 920~950℃and 0.001~0.005 s-1,and nearly complete DRX has taken place.Our results indicate that hot working property of Fe-microalloyed Ti-6 Al-4 V is better than that of Ti-6 Al-4 V alloy in 800~950℃temperature scale,and processing cost is decreased.