Observation of recrystallization upon annealing rapidly solidified microstructures of highly undercooled Ni₈₀Cu₂₀ alloys

Recrystallization in rapidly solidified microstructures was experimentally observed. Highly undercooled Ni₈₀Cu₂₀ alloy melts were quenched before rapid solidification by Ga-In liquid alloy. After the quenching, partially recrystallized microstructures were obtained. In addition, dense crystalline defects such as dislocation networks were also observed. Further annealing of the partially recrystallized microstructures produced higher degree of recrystallization microstructures. With these directly observed experimental results, one of the most probable underlying physical origins, i.e. stress induced recrystallization mechanism, of the grain refinement phenomenon occurring at high undercooling regimes in rapidly solidified microstructures is clarified.