基于3D-FEM的大型钛环热辗扩过程微观组织演变仿真

Simulation of microstructure evolution during hot rolling of large rings of titanium alloy based on 3D-FEM

基于ABAQUS/Explicit软件平台,采用弹性预估-塑性校正策略和隐式积分算法,将Ti-6Al-4V的微观组织演变模型和率相关温度相关各向同性硬化弹塑性本构模型写入子程序VUMAT,实现了微观组织演变与宏观热力行为的耦合模拟。利用Ti-6Al-4V圆柱体等温镦粗实验,对所开发子程序的可靠性进行了验证。将该子程序应用于大型钛环热辗扩过程的热力耦合3D-FE模拟中,研究了微观组织在成形过程中的演变特征及机理。研究发现,沿着成形环件的径向,中间层相对于表层具有较小的β晶粒尺寸和β体积分数。

The microstructure evolution model and the rate-dependent and temperature-dependent elastic-plastic constitutive model with isotropic hardening are implemented in ABAQUS/Explicit through the subroutine VUMAT by using the elastic predictor-plastic corrector scheme combined with the implicit integration algorithm, and thus the simulation is realized with respect to microstructure evolution coupled with macro-scale mechanical and thermal behaviors. The developed subroutine is validated by comparing with experimental results in isothermal upsetting of Ti-6Al-4V cylinder. The subroutine is imbedded into the coupled thermo-mechanical 3D-FE model for hot rolling of large rings of titanium alloy, and then the characteristics and mechanism of micro- structure evolution during the process are studied. The results obtained show that along the radial direction of the deformed ring, the middle layer has smaller β grain size and β volume fraction than the exterior layer.