Ti-5.6Al-4.8Sn-2.0Zr-1.0Mo-0.35Si-0.85Nd合金α+β两相区变形行为及工艺参数优化

Deformation behavior and process parameter optimization of Ti-5.6Al-4.8Sn-2.0Zr-1.0Mo-0.35Si-0.85Nd alloy in α+β forging process

在变形温度920~1040℃、应变速率0.001~70.0 s^(-1)条件下,采用Thermecmastor-Z热模拟试验机研究Ti-5.6Al-4.8Sn-2.0Zr-1.0Mo-0.35Si-0.85Nd合金在α+β两相区变形时的流动行为和塑性变形机制,得到优化的工艺参数范围。结果表明:该合金在α+β两相区变形时的流动应力对变形温度和应变速率均较敏感,变形温度较低时(920、950和980℃),流动应力曲线呈流动软化特征,变形温度较高时(1010和1040℃)呈稳态流动特征。失稳变形工艺参数范围为(920~930℃、0.2~70 s^(-1))和(1000~1040℃、1~70 s^(-1))范围,该区域易产生局部流动和机械失稳。综合加工图及微观组织观察结果,优化出的Ti-5.6Al-4.8Sn-2.0Zr-1.0Mo-0.35Si-0.85Nd合金α+β两相区变形时的工艺参数范围为(1000~1030℃、0.001~0.1 s^(-1))及(920~935℃、0.001~0.003 s^(-1)),其塑性变形机制为超塑性成形。

The flow behavior and plastic deformation mechanism of Ti-5.6Al-4.8Sn-2.0Zr-1.0Mo-0.35Si-0.85 Nd alloy were studied by the hot compression,which was carried out on a Thermecmastor-Z simulator in the temperature range of 920-1040 ℃and strain rate range of 0.001-70.0 s^(-1),and the optimization process parameter range was obtained.The results show that the flow stress of this alloy is sensitive to temperature and strain rate in the α+β range.The flow stress curves exhibit a flow softening behavior when the temperature is lower than or equal to 980 ℃;while the flow stress curves exhibit a steady-state characteristic when the temperature is higher than or equal to 1010 ℃.The processing map exhibits two instability fields:920-930 ℃at 0.2-70 s^(-1) and 1000-1040 ℃ at 1-70 s^(-1).In these instability fields,the flow location or mechanical instability occurs.Combining processing map with microstructure observation,the optimum deformation process parameters in α+β range for Ti-5.6Al-4.8Sn-2.0Zr-1.0Mo-0.35Si-0.85 Nd alloy are(1000-1030 ℃,0.001-0.1 s^(-1)) and(920-935 ℃,0.001-0.003 s^(-1)),respectively,and the corresponding plastic deformation mechanism is superplasticity deformation.