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

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.