BT25钛合金在锻造过程中失稳变形和动态再结晶行为的数值模拟

Numerical Simulation of Unstable Deformation and Dynamic Recrystallization Behavior of BT25 Titanium Alloy During Hot Forging

摘要:

分别利用失稳图和功率耗散图确定BT25钛合金失稳变形组织和动态再结晶变形组织的热力参数边界条件，并将其输入到Deform-3D有限元软件中，使加工图技术与有限元技术能够进行有效结合。利用二次开发后的软件对BT25钛合金在变形温度为950~1100 ℃和应变速率0.001~1 s^-1的条件下进行失稳变形组织和动态再结晶行为的模拟和预测，并通过对比金相组织，验证了该模拟结果的可靠性。结果表明，流动应力随变形温度的升高或应变速率的降低而降低；失稳变形组织集中在低温、高应变速率区域；高温和低应变速率均有利于动态再结晶（DRX）行为；微观组织的观察结果与模拟预测的结果吻合较好，说明本研究提出的加工图技术与有限元技术相结合的方法对模拟与预测金属锻造过程中的失稳变形组织和DRX行为是可行的。

关键词:BT25钛合金;失稳图;功率耗散图;失稳变形组织;动态再结晶;数值模拟

Abstract:

The thermal parameter boundary conditions of the unstable deformation microstructure and dynamic recrystallized microstructure of BT25 titanium alloy were determined by the instability maps and power dissipation maps, respectively. The results were used in the Deform-3D finite element (FE) software to effectively combine the processing map technique with FE technique. The FE codes after secondary development were used to simulate and predict the unstable deformation zones and dynamic recrystallization (DRX) behavior of BT25 titanium alloy at the deformation temperature of 950~1100 °C and the strain rate of 0.001~1 s^-1. The reliability of simulation results was verified by metallographic microstructure. Results show that the flow stress is decreased with increasing the deformation temperature or decreasing the strain rate. The unstable deformed microstructure is concentrated in the region of low temperature and high strain rate. Both high temperature and low strain rate are beneficial to DRX behavior. The results of metallographic microstructure are in good agreement with those of simulation, indicating that the method of combining processing map technique and FE technique is reliable and feasible for predicting the unstable deformed microstructure and DRX behavior in the metal forging process.

Key words:BT25 titanium alloy;instability map;power dissipation map;unstable deformation microstructure;dynamic recrystallization;numerical simulation