The article presents the results of research on the morphological changes of the γ ′ phase generated during heat treatment of the directionally crystallizing Rene 108DS alloy. The alloy was evaluated after solution heat treatment, primary aging (combined with the CVD aluminization process), additional regenerative heat treatment, and second-degree aging. Analysis of the morphology of the γ ′ phase after aluminization revealed significant growth of γ ′ phase precipitate size and content. To correct this effect, an additional heat treatment was introduced to restore the alloy microstructure to a state typical of first-degree aging. Microstructural studies confirmed the effectiveness of this process. The final heat treatment, in the form of second-degree aging, ensured the formation of the γ ′ phase with an acceptable quantitative share, size, and shape of precipitates. The main morphological features subject to significant changes during heat treatment were the share and size of the γ ′ phase. The shape of the precipitates, expressed by the sphericity coefficient and elongation, showed minor sensitivity to the heat treatment process.
Witala et al. (Thu,) studied this question.