FGH4097合金热处理过程中γ′相演变行为

Evolution Behavior of γ′ Phase in FGH4097 Alloy During Heat Treatment

摘要:

对热等静压态（hot isostatic pressure，HIP）FGH4097合金进行热处理，采用SEM和TEM等分析手段，研究了合金中γ′相在固溶和冷却过程中的溶解和析出行为。结果表明：固溶过程中，位错辅助Al、Ti原子扩散，促进γ′相分裂溶解，其中次生γ′相从中心分裂成细小的γ′相优先溶解，初生γ′相通过γ/γ′相界面向内分裂成尺寸较小的γ′相而后溶解；基于JMAK方程，建立了描述γ′相溶解的动力学方程，线性拟合相关系数R=0.9933，平均相对误差（average relative error，AARE）值为10.01%，可预测γ′相在850~1200 ℃范围内的面积分数；冷却过程中，在位错作用下，初生γ′相优先在晶界析出，沿着垂直于晶界方向不规则生长，导致弯曲晶界生成；次生γ′相在晶内析出。随着中间温度（middle temperature，MT）从1200 ℃降低至850 ℃，晶内析出的γ′相尺寸从76 nm增加到521 nm，合金显微硬度从471.45 HV减小到394.18 HV，表明合金的显微硬度随γ′相尺寸的增大而减小。

Abstract:

FGH4097 alloy was treated by the hot isostatic pressure (HIP) process. The dissolution and precipitation behavior of γ' phase in the alloy during solid solution and cooling were studied by SEM and TEM. The results show that during the solid solution process, dislocations assist the diffusion of Al and Ti atoms and promote the splitting and dissolution of γ' phase. The secondary γ' phase is preferentially dissolved by splitting into fine γ' phase, and the primary γ' phase is dissolved by splitting into smaller γ' phase through the γ/γ' phase interface. Based on the JMAK equation, a kinetic equation describing the dissolution of γ' phase was established. The linear fitting correlation coefficient R=0.9933 and the average relative error value is 10.01%, which can predict the area fraction of γ' phase in the range of 850?1200 ℃. During the cooling process, under the action of dislocations, the primary γ' phase preferentially precipitates at the grain boundary and grows irregularly along the direction perpendicular to the grain boundary, resulting in the formation of curved grain boundaries. The secondary γ' phase is precipitated in the crystal. With the decrease in intermediate temperature (MT) from 1200 ℃ to 850 ℃, the size of γ' phase precipitated in the crystal increases from 76 nm to 521 nm, and the microhardness of the alloy decreases from 471.45 HV to 394.18 HV, indicating that the microhardness of the alloy decreases with the increase in γ' phase size.