深过冷Ni-B合金再辉过程与凝固速率的研究

Research on Recalescence Process and Solidification Rate of Highly Undercooled Ni-B Alloy

为研究亚共晶Ni-B合金的共晶转变机理及再辉速率与界面生长速率的关系,采用熔融玻璃净化、循环过热和触发形核三者相结合的方法,借助高速摄影、红外测温仪对Ni-2.51wt.%B、Ni-2.79wt.%B、Ni-3.01wt.%B亚共晶合金的共晶转变再辉行为和凝固速率进行了研究。结果表明:当过冷度比较小时,亚共晶Ni-B合金的共晶转变界面生长速度很慢;但当过冷度较大时,其生长速度又变快,界面生长时间与熔体再辉时间随过冷度增大而减小,且变化趋势相似,两者的比值近似为一个定值。过冷度一定时,再辉速率和生长速率随着B含量的增加而增大;成分一定时,随过冷度的增加,三个亚共晶成分的Ni-B合金的再辉速率和生长速率都在增大,且变化趋势一致,两者的比值与过冷度呈反比例关系。

In order to study the eutectic transformation mechanism of hypoeutectic Ni-B alloys and the relationship between recalescence rate and interfacial growth rate, the melts of Ni-2.51 wt.% B, Ni-2.79 wt.%B and Ni-3.01 wt.%B hypoeutectic alloys were respectively undercooled by using molten glass fluxing technology in combination with high frequency melting and cycled superheating methods. In the circulating melting process, the high temperature resistant steel nail was used to trigger the molten metal to be solidified under a certain undercooling degree. The cooling curve and high-speed photography were obtained to analyze the recalescence phenomenon of Ni-B hypoeutectic alloy. The results show that the growth rate of hypereutectic Ni-B alloy is very slow under small undercooling, but it becomes relatively fast under large undercooling. In addition, the interface growth time and melt recalescence time decrease with increasing the undercooling, and both show a similar change trend, with an approximately fixed ratio. At the same undercooling degree(ΔT), the recalescence rate(R) and growth rate(V) increase with an increase in B content. Meanwhile, the change trend of R and V with the undercooling is the same when the composition is constant, and the ratio of V to R is inversely proportional to the undercooling.