Jieshan Hou

Precipitation Behaviors of M 23 C 6 Carbides and γʹ Phase in Cast IN617B Alloy During Long-Term Aging

The precipitation behaviors of M23C6 carbides and γʹ phase in cast IN617B alloy during long-term aging was systematically investigated by comparison with previous studying results about wrought IN617B alloy. The results showed that the morphology of M23C6 carbides and the nucleation location of γʹ particles in cast IN617B alloy were distinctly different from those of wrought IN617B alloy due to the difference of processing method. The microstructure observation revealed that the morphology of M23C6 carbides at grain boundaries (GBs) transformed from film-like shape into cellular shape owing to the reduction in the interfacial energy of GBs. Within the grains the bar-like M23C6 carbides and spherical γʹ phase directly precipitated from the γ matrix. Moreover, the growth of M23C6 facilitated the formation of γʹ phase by enriching γʹ-formation elements, and conversely, dense γʹ phase inhibited the coarsening and decomposition of M23C6 by constraining the diffusion of M23C6-formation elements. In addition, the mechanism of inhibiting effect of γʹ phase on the coarsening of bar-shaped M23C6 was discussed.