Effect of undercooling on microstructure evolution of Cu based alloys

Based on the deep undercooling rapid solidification method, the Cu based alloy has reached different undercooling degrees. The microstructure and evolution of non-equilibrium solidification of two alloys were systematically studied. It is found that grain refinement occurs in both the large undercooling range and the small undercooling range of the two alloys. EBSD technology was used to analyze the grain refinement structure, and the results showed that the grain refinement structure with large undercooling and that with small undercooling had completely different grain orientations. The grain refinement of low undercooling alloy is caused by dendrite remelting and fragmentation, while that of high undercooling alloy is completed by stress induced recrystallization. The evolution law of undercooling and microstructure hardness was systematically studied by using a microhardness tester. It was found that a sudden drop in grain size occurred near the critical undercooling, which is the direct evidence of grain refinement of non-equilibrium solidification structure of high undercooling alloy due to recrystallization.