Inflence of the undercooling on γ' phase in the DZ125 superalloy

By the method of molten salt purification combined with cycled superheating, a considerable undercooling up to 180Kis achieved in the DZ125 superalloy melt. The effect of undercooling on γ' phase in the DZ125 super alloy was analyzed. In connection with the classical nucleation and growth theory, the size and distribution of the precipitated γ' phase in the DZ125 superalloy was also controlled by the melt undercooling. With increasing melt undercooling, solid solubility of the γ' phase formers is extended, and the driving force for γ' precipitation is improved, thus the volume fraction and the number of γ' phase precipitate are enlarged, which leads to a refinement of the final γ' phase particles. Furthermore, a high density of crystalline defects and grain boundaries could be introduced in the primary solidification structure as effective nucleation sites for γ' phase, which will reduce the critical nucleation energy and favors γ' phase precipitation.