新型镍基粉末高温合金晶粒长大行为研究

Study on grain growth behavior of new Ni-based powder metallurgy superalloys

对第四代粉末高温合金FGH4108晶粒长大行为进行研究。结果表明, γ'相在完全溶解温度以下固溶处理时,晶粒长大幅度较小,与初始组织差别不大(锻态,3~4μm);当达到 γ'相完全溶解温度时,晶粒发生明显长大;超过 γ'相完全溶解温度时,晶粒尺寸大幅增加(30~40μm),过固溶的几个温度下晶粒尺寸差别不大;保温初期晶粒尺寸显著增加,一定保温时间后晶粒尺寸不再随时间明显变化。温度和时间对晶粒尺寸的影响都与 γ'相对晶界迁移的阻碍作用有关,根据温度和时间的影响,对传统晶粒长大模型中界面迁移的表观激活能(Q)、时间指数(n)和广义迁移率常数(A_(0))进行修正,构建了新的模型,模型预测值与实验值的决定系数(R^(2))为0.9997,均方误差为0.12μm,预测精度较高,晶粒长大曲线各项特征能被准确预测出来。

The grain growth behavior of the fourth generation powder metallurgy(PM)superalloys was studied.The results indicate that the grain growth range is small when the heat treatment temperature is below the γ'solution temperature,which is similar to the initial microstructure(as-forged,3~4μm).However,the grain size greatly increases to 30~40μm when the heat treatment temperature exceeds the γ'solution temperature,and there is little difference in grain size at the several temperatures over the'solution temperature.The grain size increases significantly at the initial stage of heat treatment,and no longer changes after a certain holding time.The influence of temperature and time on grain size is related to the pinning effect of γ'on grain boundary migration.A new model is established by modifying the parameters such as the activation energy for boundary migration(Q),the time exponent(n),and the generalized mobility constant(A_(0))based on the traditional grain growth model.The determination coefficient(R^(2))and the meansquare error(MSE)between the predicted and the experimental values are 0.9997 and 0.12μm,respectively,showing the high prediction accuracy,and the various characteristics of the grain growth curves can also be predicted accurately.