摘要
采用大体积液态金属的微观净化技术 ,在Ni Ni3 Sn合金系中使Ni (2 .5～ 17.5 )at%Sn和Ni (17.8～ 2 5 .0 )at%Sn两组合金分别获得了最大达 35 1K和 30 3.5K的“极限”形核过冷度 ,并使其极限过冷度保持 30个循环过热周期不衰减 .实验发现 ,Ni Ni3 Sn系近共晶合金深过冷凝固时 ,Ni3 Sn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Ni3 Sn和α(Ni)相异质形核时的异质形核因子f(θ)分别为 0 .0 810 3和 0 .12 4 0 6 ;求得过冷熔体中Ni3 Si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边 ,表明在近共晶成分过冷熔体中 ,金属间化合物Ni3 Sn易于α(Ni)
The micro denucleation technique of bulk melt was applied to Ni Ni 3Sn alloy system. In two composition ranges of Ni (2.7～17.5)at%Sn and Ni (17.8～25.0)at%Sn, the alloys were undercooled up to the highest undercooling of 351K and 303.5 K respectively. The highest undercooling could be held for 30 melting superheating cooling circles. The experimental results indicated that, during the solidification of the alloys with compositions closed to the eutectic composition in Ni Ni 3Sn alloy system,Ni 3Sn was always nucleated heterogeneously ahead of α(Ni) phase . The catalytic factors f(θ) of Ni 3Sn and α (Ni) were 0.124 06 and 0.081 03 respectively, calculated with the experimental data and the kinetic model of heterogeneous surface nucleation. The temperature versus composition curve with the same nucleation rate for Ni 3Sn and α (Ni) lay at the left side of eutectic point completely, which indicated that in the undercooled melts closed to the eutectic composition the nucleation of faceted Ni 3Sn phase was easier than that of α (N) phase.
出处
《西安工业学院学报》
2002年第1期56-61,共6页
Journal of Xi'an Institute of Technology
基金
国家自然科学基金 (5 96 0 10 11)
