热变形参数对GH864合金显微组织的影响

Effects of Hot-Working Parameters on Microstructure of GH864 Superalloy

摘要:

采用等温热压缩的方法研究了在变形温度为1000~1160 ℃、应变速率为1和10 s-1、工程应变量为30%, 50%和70%时，不同的热变形参数对GH864合金流变应力和显微组织的影响。结果表明，当变形温度低于γ′相析出温度时，动态再结晶能力较差。在高于MC碳化物的回溶温度变形时，由于沿晶界再析出的细小MC颗粒对晶界的非均匀钉扎作用，容易得到混晶严重的热处理态组织。降低变形速率和增加变形量可以得到较为均匀的变形态组织，最终改善热处理态的混晶程度。GH864合金热变形温度的下限和上限分别为γ′相的析出温度和MC碳化物的回溶温度

Abstract:

The effects of hot working parameters on flow stress and microstructure of GH864 superalloy were studied by isothermal compressive deformation at deformation temperatures from 1000 to 1160 oC, strain rates of 1 and 10 s-1 and engineering strain of 30%, 50% and 70%. The results show that the deformation temperature has great influence on the ultimate as-heat treated grain size and morphology of carbides on grain boundary. When the temperature is below the γ′ precipitation temperature, the dynamic recrystallization capability is bad. While when the temperature is high enough to resolve MC carbides, severely duplex grain structure and feather-like carbide around smaller grains can be easily formed because of the non-uniform pinning effect of re-precipitated fine MC particles on grain boundary, and all these unfavorable characteristics can be partially eliminated by improving hot deformed structure through increasing strain and decreasing strain rate. The ideal deformation temperature should be confined between γ′ precipitation temperature and dissolution of MC carbide