Ti-Al-Nb合金的热变形与动态再结晶行为研究

Thermal Deformation and Dynamic Recrystallization of Ti-Al-Nb Alloys

目的建立本构方程及动态再结晶模型,描述热变形条件对Ti-Al-Nb合金动态再结晶以及合金软化的影响规律。方法基于热模拟压缩变形试验,获得Ti-Al-Nb系合金在不同热变形工艺参数下的应力应变曲线。采用双曲正弦模型表征流动应力,通过线性回归等数据处理方式求得各参数的具体数值。结果求得动态再结晶活化能Q=197.626 kJ/mol,材料常数A的平均值为3.173×10^6,建立流动应力本构方程。Z/A为无量纲参数,通过最小二乘线性拟合求得ε^*=344×10^5(Z/A)^0.495,εc=16.15(Z/A)^0.24。结论Ti-Al-Nb系合金在峰值应力出现之前均发生了动态再结晶:当应变速率较高时,在流动稳定前会发生强烈的软化,曲线显现双峰;当应变速率较低时,在加工硬化和软化作用达到平衡后逐渐进入稳定阶段,此时曲线显现单峰。研究结果将为Ti-Al-Nb系合金的精密塑性成形提供一定的技术参考和理论依据。

The purpose of this paper is to establish constitutive equation and dynamic recrystallization model to describe the influence of thermal deformation conditions on dynamic recrystallization and alloy softening of Ti-Al-Nb alloy.Based on the thermal simulation compression deformation experiment,the stress-strain curves of Ti-Al-Nb alloy under different thermal deformation parameters were obtained.The flow stress was characterized by hyperbolic sinusoidal model.The specific values of each parameter were obtained by linear regression and other data processing methods.The dynamic recrystallization activation energy Q=197.626 kJ/mol was calculated,and the average material constant A was 3.173×10^6.The constitutive equation of flow stress was established.Z/A was dimensionless parameter.ε^*=344×10^5(Z/A)^0.495 andεc=16.15(Z/A)^0.24 were obtained by least squares linear fitting.The results show that under the experimental conditions,dynamic recrystallization occurs before the peak stress occurs;at high strain rate,strong softening of materials occurs and double peaks appear before stabilization;at low strain rate,material stabilizes gradually and single peak appears after balance between work hardening and softening.The results of this study will provide a theoretical basis and technical reference for the precision plastic forming of Ti-Al-Nb alloy.