凝固速率对铌基共晶自生复合材料定向凝固组织的影响

Effect of Solidifying Rate on Directionally Solidified Microstructure of Niobium Based In-Situ Composites

摘要:

铌基共晶自生复合材料（NBISC）经真空自耗电弧熔炼成母合金锭，采用高温度梯度的电子束区熔装置制备定向凝固的试样，分析其组织特征。结果表明：Nb基固溶体（Nbss）相、（Nb，Ti）3Si相和（Nb，Ti）5Si3相为NBISC材料的主要组成相；在电了束区熔条件下，随着电子枪移动速率的提高，NBISC材料共晶组织变细，组织中片层状的共晶团增多，块状或板条状的（Nb，Ti）3Si／（Nb，Ti）5Si3相尺度减小、数量增多，组织趋于规则、分布更均匀，组织的定向性增强，定向效果显著。

Abstract:

An ingot of Nb based in-situ composites (NBISC) was produced by a vacuum self-consuming arc melting furnace. The directionally solidified samples were prepared by an electron beam floating zone melting (EBFZM) furnace with a high temperature gradient, and their microstructural characteristics were analyzed. The results show that the microstructure of as-cast NBISC is composed of primary dendrites of Nb solid solution (Nbss) and the eutectic colonies of Nbss plus (Nb,Ti)3Si/(Nb,Ti)5Si 3. In the EBFZM furnace, with the increase of withdrawing rate, the eutectic microstructure of NBISC is refined. The amount of eutectic colonies layers increases. The sizes of (Nb,Ti)3Si/(Nb,Ti)5Si3 lumps or plates decrease and their amount increases. Their morphology tends to more regular, and the distribution becomes more homogeneous. The directionality becomes intensive and the directionally solidified effects are remarkable.