铌硅化物基超高温合金电弧熔炼态组织和成分分布

Microstructure and Compositional Distribution in Arc-melted Advanced Nb-silicide-based Ultrahigh Temperature Alloy

采用真空非自耗电弧熔炼后再真空自耗电弧熔炼的方法制备了Nb-Ti-Si-Cr-Al-Hf-Mo-B-Y超高温合金的母合金锭,分析了合金锭不同位置的组织形貌、相组成和成分分布特点。结果表明:母合金锭主要由Nbss,(Nb,X)5Si3和(Nb,X)3Si三相组成。母合金锭组织主要由初生Nbss枝晶,花瓣状Nbss+(Nb,X)5Si3共晶和块状(Nb,X)3Si组成;但在母合金锭底部和顶部的中心部位组织却由分布均匀的Nbss+(Nb,X)5Si3共晶组成,没有出现初生树枝状Nbss和块状(Nb,X)3Si。母合金锭中的成分分布特点为Si由锭边缘向中央逐渐升高,Ti由边缘向中央逐渐递减。

The ingot of Nb-Ti-Si-Cr-Al-Hf-Mo-B-Y ultrahigh temperature alloy was prepared by firstly vacuum non-consumable arc melting and then vacuum consumable arc melting. The microstructures, constituent phases and compositional distribution in the master alloy ingot were analyzed. The results showed that the main constituent phases of the ingot were Nb solid solution （Nbss）, （Nb,X）3Si and （Nb,X）5Si3 （where X represents Ti, Hf and Cr elements）. The microstructure of the ingot mostly consisted of primary Nbss dendrites, Nbss＋（Nb, X）5Si3 eutectic colonies （lamellar or petal-like） and （Nb,X）3Si blocks. However, the microstructure in the central parts of both the top and bottom of the ingot was composed of Nbss＋（Nb,X）5Si3 eutectic colonies, with little primary Nbss dendrites or （Nb,X）3Si blocks. The compositional distribution was not uniform in the master alloy ingot. The Si content increased from the edge part to the central part, and the Ti content decreased from the edge part to the central part of the ingot.