铌在铀熔体中的溶解扩散行为研究

Research on the Dissolution and Diffusion of Niobium in Uranium Melt

摘要:

铀铌合金具有优异的抗腐蚀性能和良好的综合力学性能，是核工程中重要的结构与功能材料。通过直接真空感应熔炼的方式实现铀铌合金的合金化，可大幅度提高铀铌合金的生产效率。然而，铀铌合金的真空感应熔炼合金化过程易出现合金化不充分的现象，该问题主要与固态铌在铀熔体中的溶解扩散过程有关。为了提高对固态铌在铀熔体中的溶解扩散的认识，精确优化铀铌合金的真空感应熔炼工艺，提升铀铌合金材料质量，本文对固态铌在铀熔体中的溶解扩散行为进行了研究。通过溶解扩散实验获得铌在铀熔体中的溶解速率v与熔体温度T存在v=0.3651exp(-21150[K]/T)[m/s]关系；对U/Nb溶解扩散界面进行了表征，结果显示铌溶解于铀熔体的过程中，U/Nb溶解扩散界面形成了与固态Nb存在位向关系的片状结构；对比有无电磁搅拌情况下铌在铀熔体中的溶解行为及U/Nb界面结构，结果表明电磁搅拌提高了铌在铀中的溶解速率并改变了U/Nb界面的片状结构。

Abstract:

Uranium-niobium (U-Nb) alloys have excellent corrosion resistance and good mechanical properties. They are good candidates for structural materials and functional materials of nuclear engineering. Fabrication of high quality uranium-niobium alloys using direct vacuum induction melting process is of great significance for efficiency promotion. But unsufficient alloying is the main problem of U-Nb alloy fabricated by direct vacuum induction melting process. The dissolution and diffusion of solid Nb in U melt is the key point of direct vacuum induction melting process of U-Nb alloy. So, in this paper, we investigated the dissolution and diffusion of Nb in U melt using experimental method. The actual dissolution rate of Nb in U melt with different temperature was obtained. The dissolution rate of Nb in U melt v and the melt temperature T have a relation of v=0.3651exp(-21150[K]/T)[m/s]. Scanning electron microscope observation shows sheet structure forms at the U/Nb interface during the dissolution process of Nb in U melt. When electromagnetic stirring is used, the dissolution rate of Nb in U melt increases obviously and the morphology of sheet structure at the U/Nb interface changes.