对熔融玻璃净化后深过冷Ni-21.4%Si(原子分数, 下同)共晶合金的凝固特性进行了实验研究, 并对其均质形核过冷度进行了理论预测. 结果发现, 采用熔融玻璃净化可使Ni-21.4%Si共晶合金获得318 K的过冷度. 理论计算表明, 此过冷度达到了Ni-21.4%Si共晶合金的均质形核过冷度. Ni-21.4%Si共晶合金凝固特性与过冷度?T有关: 当过冷度小于250 K时, 冷却曲线有2个再辉峰, 其中当过冷度小于206 K时, 凝固组织由Ni3Si相和规则共晶组成, 当过冷度在206 K到250 K之间时, 凝固组织由α-Ni相和规则共晶组成; 过冷度大于250 K后, 冷却曲线只有 1个再辉峰, 凝固组织为反常共晶. 过冷度会影响初生相Ni3}$Si的生长方式. 随着过冷度的增大, 初生相Ni3Si<的生长会由小平面生长方式转为非小平面生长方式.
The solidification behaviors of highly undercooled Ni-21.4%Si eutectic alloy molten under a slag composed of B2O3 and soda lime glass were investigated and the undercooling for the alloy to nucleate homogenously was predicted theoretically. It is found that a undercooling of 318 K can be achieved in Ni-21.4%Si eutectic alloy by using slag technique. Theoretical calculation shows that the maximum undercooling obtained in Ni-21.4%Si eutectic alloy has reached the homogeneous nucleation undercooling for the alloy. The solidification behavior and structure of undercooled Ni-21.4%Si eutectic alloy depend on the undercooling. When the undercooling is lower than 250 K, there are two recalescence peaks on the cooling curve. The solidified microstructure is composed of primary Ni3Si phase and regular eutectic as the undercooling is lower than 206 K, while primary α-Ni phase and regular eutectic structure are obtained when the undercooling is in the region from 206 K to 250 K. When the undercooling is greater than 250 K, only one recalescence peak is observed in the cooling curve and anomalous eutectic structure is obtained. Undercooling can influence the growth mode of primary Ni3Si. The primary Ni$_{3}$Si transforms from lateral growth to non-lateral growth with increasing the undercooling.
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