4 结论

　　采用熔融玻璃结合循环加热的方法，研究了Ni80B20合金熔体深过冷快速凝固中的相竞争规律。主要结论如下：

　　(1)组织演化表明，当Ni80B20合金过冷度大180K时，在竞争形核中Ni3B作为初生相从熔体析出。反之，Ni(α)作为初生相从熔体析出

　　(2) 当Ni80B20合金过冷度小于180K时，Ni(α)的孕育时间短，Ni(α)首先形核，且由于Ni(α)的生长速度相对较大，Ni(α)呈枝晶形态;过冷度大于180K时，Ni3B的孕育时间短，Ni3B作为初生相，且Ni3B的生长速度相对较小，Ni3B呈球状。形核很大程度上决定相形成的竞争，而生长很大程度上决定相形态的竞争。

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