Abstract: Through creep property test and microstructure observation, the effect of heat treatment on microstructure and creep behavior of directionally solidified alloy DZ125 was studied. The results show that there are many radial eutectic structures in the interdendritic region of the as-cast alloy, and part of the γ′ phases between dendrites and dendrite stems are butterfly shaped, and the sizes of γ′ phase are quite different. The eutectic structures and γ′ phases of the as-cast alloy are dissolved during the solid solution process, and the fine rhombohedral γ′ phase precipitated from the matrix during the subsequent cooling process. During the first aging period, the small γ′ phases similar to rhombus are blunted and grown until it transformed into a cube shape. During the secondary aging, the size of the γ′ phase is basically unchanged, but the cubic degree increases, and the microstructure of the alloy is that the γ′ phase precipitated from the matrix in a coherent manner. During the heat treatment process, the eutectic structures in the alloy are basically eliminated and the cubic degree of the phase is improved, but the structure inhomogeneity in the alloy is not eliminated. The cubic γ′ phase in the dendrite stem region is small in size, while the cubic γ′ phase in the interdendritic region is coarse in size, and the alloy has good anti-creep properties at 980 ℃.

Key words: DZ125 nickel-based superalloy, heat treatment, microstructure, creep properties