采用大体积液态金属的微观净化技术，在Ni—Ni3Si合金系中使Ni-（6．07—19．7）％Si和Ni-（20.5—22）％Si两组合金分别获得了最大达344和265K的极限形核过冷度，并使其极限过冷度保持20个循环过热周期不衰减.实验发现，Ni—Ni3Si系近共晶合金深过冷凝固时，Ni3Si总是领先于α（Ni）相形核.根据实验数据和表面异质形核速率模型，求得Ni3Si和α（Ni）相异质形核时的异质形校因子f（θ）分别为0．069和0.28;求得过冷熔体中Ni3Si和α（Ni）相等形核速率时的温度-成分曲线完全处于共晶点左侧，表明在近共晶成分过冷熔体中，小平面相Ni3Si易于α（Ni）形核
The micro-denucleation technique of bulk melt was applied to Ni-Ni3Si alloy system. In two composition ranges of Ni-(6.07 - 19.7)%Si and Ni-(20.5 - 22)%Si, the alloys were undercooled up to the highest undercooling of 344 and 265 K respectively. The highest undercooling could be held for 20 melting-superheating-cooling circles. The experimental results indicated that, during the solidification of the alloys with compositions closed to the eutectic composition in Ni-Ni3Si alloy system, Ni3Si was always nucleated heterogeneously ahead of α(Ni) phase. The catalytic factors f(θ) of Ni3Si and α(Ni) were 0.069 and 0.28 respectively,calculated with the experimental data and the kinetic model of heterogeneous surface nucleation.The temperature vs composition curve with the same nucleation rate for Ni3Si and α(Ni) lay on the left side of eutectic point completely, which indicated that in the undercooled melts closed to the eutectic composition the nucleation of faceted Ni3Si phase was easier than that of α(Ni)phase.
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