The microstructural evolution and mechanism of grain refinement during rapid solidification of Ni–Cu alloys were studied by molten glass purification and cyclic superheating. The maximum undercooling has achieved 320 K for Ni65Cu35, 295 K for Ni55Cu45 and 280 K for Ni50Cu50 alloys. Two mechanisms were found to be responsible for the grain refinements under small undercooling and large undercooling, respectively. The grain refinement at small undercooling is mainly caused by dendrite superheating and remelting, whereas that for large undercooling is mainly due to recrystallization occurred at high angle grain boundary and high proportion of twin boundaries. Meanwhile, almost no dislocations and other defects were observed in the substructure of the alloy with large undercooling.The average microhardness was found a sharp decrease in the alloy with large undercooling, which indicates that the plastic strain accumulated in the microstructure formed under large undercooling is completely dissipated in post-recalescence, and the deformation energy can offer the driving force for recrystallization in the microstructure.

通过熔融玻璃净化和循环过热研究了镍铜合金快速凝固过程中晶粒的组织演变和细化机理。Ni65Cu35合金的最大过冷度达到320 K，Ni55Cu45合金的最大过冷度为295 K，Ni50Cu50合金的最大过冷度为280K。发现有两种机制分别负责小过冷和大过冷下的晶粒细化。过冷度小的晶粒细化主要是由于枝晶的过热和重熔引起的，而过冷度大的晶粒细化主要是由于在高角度晶界和高比例孪晶边界处发生了再结晶。同时，在过冷度大的合金的亚结构中几乎没有观察到位错和其他缺陷。