1995 Volume 35 Issue 5 Pages 524-530
The precipitation and growth behaviors of δ phase in Ni-base superalloy, modified Inconel X-750 type alloy (X-750M), were investigated mainly by optical and transmission electron microscopy. The strengthening phase in the aged X-750M was metastable γ" phase. The γ" phase changed gradually into the stable δ phase during aging. The orientation relationship between γ and δ phase in the cellular and the Widmanstätten precipitates was: {111}γ//(010)δ, <110>γ//[100]δ. The interlamellar spacing of the δ phase in each recipitation type was inversely proportional to the degree of undercooling below the equilibrium transformation temperature of γ phase to δ+γ phases. According to the theory of diffusion controlled eutectoidal growth, the equilibrium transformation temperatures of the cellular and the Widmanstätten precipitation were estimated to be 1279 and 1313K, respectively. These temperatures were consistent with the experimental tendency.
