Interfacial Reaction Between Zirconium Alloy Melts And Several Mold Materials

Zirconium alloy has excellent corrosion resistance and good compatibility withnuclear fuel. Being known as the “most promising material in21century”, zirconiumalloy has wide-range applications in the fields of atomic energy, chemical industry,medical facilities and so on. In the casting process, the active metal zirconium alloyneeds strict requirement with the chemical stability of the molding material. Usingcommon refractory material for molding can seriously pollute the molten zirconium andaffect the surface quality of the castings. For the interfacial reactions between activemetals and molding materials, the research is mainly focused on the titanium alloy, butvery little on zirconium. So it is of significance to research on interfacial reactionbetween zirconium and molding materials and its reaction behavior for zirconium alloycasting process.Y2O3、ZrO2and Al2O3molds were produced by investment casting, and the graphitemold was prepared by machining. The sample of zirconium alloy was poured in thevacuum arc skull furnace. The interfacial reaction layers were analyzed with XRD、EDS、SEM and so on. The results showed that the surface of the zirconium castingsamples were polluted by all elements of molding materials and formed new compounds.The interfacial reaction between Al2O3and zirconium was the most serious. The brittlereaction layers whose properties were different to the matrix metal were formed on thesurface. The other three molds diffused into the molten zirconium. The diffusion layershad a good continuity with the matrix metal.In the aspect of the modynamics, the interfacial reactions between zirconium andmold materials were analyzed by DSC. The results showed that interfacial reactions wereall happened below the melting point of zirconium. The chemical stability of Al2O3tozirconium was worst and Y2O3、graphite were best. With the Miedema model onformation heat of alloys, the activity of molten zirconium was calculated. Al can reducethe activity of molten zirconium and prevent O from diffusing to the matrix metal. Yimproves the activity of molten zirconium. Because of Y, O from Y2O3diffuses a littlefurther than O from ZrO2. At last, combining above research results, the interfacial reaction mechanismbetween molding materials and molten zirconium was analyzed with phase diagram.From the research results of this article, Al2O3can not be used for casting zirconium, andY2O3、ZrO2and graphite are applicable.