晶界一次γ'相对GH4720Li合金晶粒长大行为的影响

Influence of grain boundary primaryγ'precipitates on grain growth behavior of GH4720Li superalloy

对锻态GH4720Li合金进行了不同温度与时间的等温热处理,定量分析了其晶粒尺寸、强化相体积分数与尺寸,研究了1050~1160℃加热时锻态GH4720Li合金晶界一次γ'相的溶解与晶粒长大规律,分析了晶界一次γ'相对合金晶粒长大行为的影响。结果表明:当晶界一次γ'相的尺寸小于3.5μm时,其对晶界的钉扎作用减弱,合金的晶粒尺寸发生明显的长大。而当加热温度高于1150℃时,由于强化相的大量溶解,晶粒发生异常长大。从动力学角度分析了晶界处不同尺寸一次γ'相的合金的晶粒长大规律,随后采用Arrhenius型方程建立了表征GH4720Li合金晶粒长大行为的动力学模型,并对模型的预测精度进行了评价。

As-forged GH4720Li superalloy was isothermally heat treated at different temperatures for different time,and the grain size,volume fraction and particle size of primaryγ'phase were quantitatively characterized.The dissolution and grain growth behavior of grain boundary primaryγ'phase of the as-forged GH4720Li superalloy during heating at 1050-1160℃were studied,and the influence of grain boundary primaryγ'phase on the grain growth behavior of the superalloy was analyzed.The results show that when the size of the grain boundary primaryγ'phase is less than 3.5μm,the pinning effect on grain boundary is weakened,which leads the grain size of the superalloy to grow obviously.When the heat treatment temperature is higher than 1150℃,the grain grows abnormally due to the large amount of dissolution of the strengthened phase.The grain growth law of the superalloy with different sizes of grain boundary primaryγ'phases is analyzed from the kinetic point of view,the kinetic model to characterize the grain growth behavior of the GH4720Li superalloy is established by using Arrhenius equation,and the prediction accuracy of the model is evaluated by the experiment results.