深过冷Ni-Cu-Si合金熔体中的快速枝晶生长

摘要

For discovering the dendrite growth mechanism in multicomponent alloys, deep undercooling and subsequent rapid solidification of Ni-10％ Cu-10％ Si ternary alloy are achieved by employing the electromagnetic levitation processing technique. The maximum undercooling of 236K is obtained in experiments. The dendrite growth velocity of α-Ni, the primary phase, is measured, and the results indicate that the velocity depends on undercooling with a power function relationship as V = 1. 6 × 10-13 ΔT5.7. A comparative analyse shows that the solute of Si has significant influence on the dendrite growth of α-Ni during rapid solidification, conversely the influence of the solute of Cu is negligible. With the undercooling increasing,no transition of the microstructure of α-Ni from dendrite to equiaxed grains occurs, but the grains of α-Ni refined abruptly.%为了揭示多元合金中的枝晶生长规律,采用电磁悬浮技术实现了Ni-10%Cu-10%Si三元合金的深过冷与快速凝固,实验中合金熔体获得的最大过冷度为236K.对合金快速凝固过程中初生相α-Ni的枝晶生长速度测定结果表明,其与过冷度之间存在幂函数关系:V=1,6×10-133△5.7.当△T较小时,随着△T的增加V增加缓慢,当△T较大时,随着△T的增加V迅速增加.对比分析表明,溶质Si对α-Ni枝晶的生长影响显著,而溶质Cu则几乎没有影响.随着过冷度的增加,未发现α-Ni相的微观形态从枝晶向等轴晶转变,但α-Ni晶粒尺寸均随着过冷度的增加而急剧细化.