热等静压态TC4钛合金高温变形行为研究

Study on High Temperature Deformation Behavior of HIP TC4 Titanium Alloy

在不同变形温度(T=850-1050℃)和不同应变速率(ε=0.001~5s^-1)下采用Gleeble-1500D热模拟试验机对热等静压态TC4钛合金进行了高温热压缩试验,分析了真应力-真应变曲线特征及热变形参数对显微组织的影响,建立适用于热等静压态TC4钛合金高温流动行为的Arrhenius方程及DMM(动态材料模型)加工图。结果表明:峰值应力随应变速率的增大及变形温度的降低而增大;显微组织随变形温度升高发生马氏体相变,随应变速率增大,β相析出次生α′相,且T=900℃、ε=0.01s^-1时获得(α+β)双态组织,表明该条件能够改善材料加工性能。误差分析表明,峰值应力计算值与试验值平均相对误差绝对值仅6.77%,证明建立的本构方程能够准确预测材料高温变形时的流动应力。加工图分析表明材料流动失稳区为T=850-950℃、ε>0.6s^-1,最佳加工区间为T=850-950℃、ε=0.01~0.1s^-1。

High temperature compression tests of hot isostatic TC4 titanium alloy were carried out by using Gleeble-1500D thermal simulation machine at different deformation temperatures (T=850-1050℃ )and different strain rates (ε=0.001-5s^-1).The characteristics of true stress-strain curves and the influence of thermal deformation parameters on microstructure were analyzed.The Arrhenius equation and DMM (dynamic material model)processing diagram for hot isostatic TC4 titanium alloy flow behavior at high temperature were established.The results show that the peak stress increases with the increase of strain rate and the decrease of deformation temperature.The martensitic transformation occurs with the increase of deformation temperature.With the increase of strain rate,the secondary α′phase is precipitated in β phase,and the (α+β)double state microstructure is obtained at T=900℃ and ε=0.01s^-1,which indicates that this condition can improve the processing property of the material.The error analysis shows that the absolute value of relative error between the calculated peak stress and the experimental value is only 6.77%.It is proved that the established constitutive equation can accurately predict the flow stress of materials under high temperature deformation.The analysis of processing map shows that the instability region of material flow is T=850-950℃ and ε>0.6s^-1,and the optimum processing interval is T=850-950℃ and ε=0.01-0.1s^-1.