Grain refinement mechanism at high undercooling of Ni₈₀Cu₂₀ alloy

The mechanism of grain refinement at large undercooling was systematically studied. Maximum undercooling of about 300 K of Ni₈₀Cu₂₀ alloy was achieved using molten glass purification and cyclic superheating methods. The recrystallization mechanism of grain refinement at large undercooling was verified by means of quenching and annealing. Quenching before recalescence with Ga–In–Sn liquid alloy, the microstructure of the quenched Ni₈₀Cu₂₀ alloy consisted of equiaxed grains and fine dendrites, which were obviously partially recrystallized microstructures. Annealing the quenched alloy, dendrites fragments were replaced by the equiaxed grains result from recrystallization. At the same time, the increase of high angle grain boundaries and ∑3 twins boundaries, the reduction of texture intensity and hardness further verified the recrystallization mechanism of grain refinement at high undercooling regime. (paper)