挤压态镍基粉末高温合金热变形行为与组织研究

Study on hot deformation behavior and microstructure characteristics of extruded Ni-base powder metallurgy superalloy

通过Gleeble－3500D热力模拟研究了挤压态镍基粉末高温合金在恒温和恒应变速率条件下的热变形行为和组织特征，变形温度范围为950～1150℃，应变速率范围为0．001—0．5s^-1。通过线性回归分析，获得了挤压态镍基粉末高温合金的本构方程，并求得热变形激活能为338．638kJ·mol^-1。在1050℃以下热压缩变形时，试样容易开裂；而在1050～1150℃的温度范围热压缩变形时，试样不易开裂。挤压态镍基粉末高温合金热压缩变形后发生了完全再结晶，再结晶晶粒尺寸受温度影响显著，在低于1100℃变形时，再结晶晶粒尺寸随变形温度升高稍有增大；而在高于1100℃变形时，再结晶晶粒尺寸随变形温度升高显著增大。该种合金的合理变形参数范围为0．001—0．01s^-1及1050～1100℃。

Hot deformation behavior and microstructure characteristics of extruded Ni-base P/M superalloy under constant temperature and strain rate were studied using isothermal compression tests. The compression tests were conducted at 950 - 1150 % with the strain rate of O. 001 -0. 5 s^-1 on Gleeble- 3500D simulator. By regression analysis, the constitutive equation for Ni-base P/M superalloy was developed with hot activation energy of 338. 638 kJ · mol^-1. The Ni -base P/M superalloy specimens compressed below 1050 ℃ were more likely to crack than that compressed between 1050 -1150 ℃. Full dynamical recrystallization occured in all specimens after hot compression deformation, and the recrystallization grain size was significantly affected by temperature. When specimens deformed, with the increasing of temperature, the grain size increased slightly below 1100 ℃, while the grain size increased rapidly above 1100 ℃. The appropriate hot deformation process parameters were strain rate of 0 001 -0. 01 s^-1 and temperature between 1050 and 1100 ℃ .