Comparison of refinement mechanism between Ni₇₀Cu₃₀ and Ni-based superalloy

The microstructure and grain refinement mechanism of fine annealing hexagonal grains from the undercooled Ni₇₀Cu₃₀ alloy and commercial DD3 superalloys were compared. The undercooling experiment applied molten glass and molten salt in denucleating and high frequency induction heating of the alloys under the protection of argon atmosphere. Dendritic distortion and disintegration occured during the undercooling of alloys. The dendritic distortion was due to high strain energy produced in rapid liquid-solid phase transformation process.