The chemical composition variation of the TiAl-4722 alloys was examinedin a batch of the industrial scale master ingots, and in the corresponding castingsprepared by conventional vacuum arc remelting (VAR) combined with induction skullmelting (ISM) and investment casting processes. The content changes of majorelements and interstitial elements were evaluated based on the chemical analysisat the top and bottom of the ingots and castings. Results show that the contents ofC, N, H, Fe and Si have almost no change in the ingots and castings, suggestingthat the chemical analysis on these elements can be based on the batch analysis.The O content keeps almost the same in different ingots, but exhibits relatively largedifferences in castings, which was probably influenced by the reaction between the shellmold and the molten alloy, and the spalling of face coat of the shell mold during casting.For the major elements of Al, Nb and Cr, the composition difference between the topand the bottom of the ingots is less than that of the castings. But for the O element, thetrend is different, especially for the castings, suggesting that the investment casting is ahomogenization process for Cr and Nb, but a differentiation process for O. The contentsof major elements in castings fluctuate mainly in the same range as that in the ingots,indicating that the contents of the major elements are controllable during investmentcasting.
展开▼
