Refinement of gamma ' precipitate with melt undercooling in nickel-based superalloy

The effect of melt undercooling on the gamma ' precipitation is investigate d in nickel-based superalloy by employing the method of molten salt denucle ating combined with thermal cycles. The application of SEM and TEM techniqu e allows to further confirm and interpret gamma ' formation mechanism here. In connection with the classical nucleation theory, it is found that not o nly the size of precipitated gamma ' but its distribution in the as-solidif ied structure is also drastically influenced by the melt undercooling.