车用铸态Ti-5.5Al合金热压缩变形行为研究

Thermal compression deformation behavior of as-cast Ti-5.5Al alloy for vehicle

用铸态Ti-5.5Al-3.0Nb-3.0Zr-1.2Mo合金为基材,在Gleeble-3800D热模拟测试机上高温压缩测试,变形温度为750~900℃,变形速率为0.001~1 s^(-1),总变形比例为75%。结果表明:应变提高,铸态合金加工硬化明显,流变应力呈直线增大;到达峰值应力后,组织开始软化,在软化与硬化过程达动态平衡时,获得稳定流变。处于低变形温度下,动态软化受应变率影响最明显,合金软化受变形温度与应变率共同作用。升温至850℃,存在动态再结晶现象,表现为动态回复。以较低应变率变形时,促进动态再结晶的快速完成,α相可促进动态再结晶转变。提高应变率后,合金中的β相软化机制由动态再结晶转变成局部塑性流变。

The as-cast Ti-5.5 Al-3.0 Nb-3.0 Zr-1.2 Mo alloy was used as the substrate for the high-temperature compression test on Gleeble-3800 D thermal simulation test machine. The controlled deformation temperature was between 750 ℃ and 900 ℃,and the deformation rate was 0.001-1 s^(-1),with the total deformation ratio of 75%. The results show that as the strain degree gradually increases,the as-cast Ti-5.5 Al-3.0 Nb-3.0 Zr-1.2 Mo alloy presents obvious work-hardening phenomenon,and the flow stress increases linearly. After reaching the peak stress,the structures began to be soften. The stable rheology is obtained when the softening and hardening process reach a dynamic balance. At low deformation temperature,the dynamic softening degree is affected by the deformation rate most intensely,and the softening state of the alloy is both affected by the deformation temperature and deformation rate. After the temperature increase to 850 ℃,dynamic recrystallization occurres,which shows dynamic recovery. When deforming at a low rate,the dynamic recrystallization process accelerates,and the α phase promotes the dynamic recrystallization transition. After the deformation rate increases,the phase softening mechanism of β phase in the alloy changes from the dynamic recrystallization process to the local plastic flow state.