Nb-Ti-Cr-Si基超高温合金有坩埚整体定向凝固组织的演化

The Microstructural Evolution of Nb-Ti-Cr-Si Based Ultrahigh Temperature Alloy by Integrally Directional Solidification with Crucible

分析了Nb-Ti-Cr-Si基超高温合金有坩埚整体定向凝固试样不同区域的组织,结果表明未熔区的组织由初生相Nbss、块状的(Nb,X)5Si3和少量的小块状Cr2Nb组成。在过渡区初生相Nbss依附在未熔区的Nbss优先生长,Nbss/(Nb,X)5Si3共晶组织生长比较混乱,在初生相Nbss枝晶间出现了富Ti的Nbss/Cr2Nb共晶团。稳态区组织中Nbss和(Nb,X)5Si3定向排列,实现了整体定向凝固。固/液界面形态为树枝状,在糊状区出现了Nbss/(Nb,X)5Si3、富Ti的Nbss/(Nb,X)5Si3和Nbss/Cr2Nb三种共晶组织,根据组织分析的结果并总结了其凝固路径,测试了不同区域组织的显微硬度,结果表明稳态区的(Nb,X)5Si3的显微硬度最高。

The microstructures of different zone in the integrally directionally solidificational samples were ana- lyzed. The results showed that the microstruetures in un-remelted zone were composed of primary Nbss, block （Nb, X）s Sis and Cr2 Nb. In the initial transient zone, the primary Nbss adjoined the solid Nbss, and the Nbss/（Nb, X）5 Si3 eutectie was distributed in a mess, and the Nbss/（Nb, X）5 Si3 eutectic were presented among the primary Nbss dendrites. In the steady zone, primary Nbss and （Nb, X）5Si3 were distributed alignment. The morphology of solid/liquid interface showed dendrites, and Nbss/（Nb, X）5Si3 eutectic, Ti-rieh Nbss/（Nb, X）5Si3 eutectic and Nbss/Cr2 Nb eu- tectic were presented in the mushy zone, and the solidification path was deduced. The microhardness of microstrueture in different zone were measured, and the mierohardness of （Nb,X）5 Si3 in the steady zone reached maxium.