Microstructure evolution and mechanical properties of Ti-48Al alloy melted by double-scale yttrium oxide crucible

Ti-48Al-xY (x = 0, 0.1, 0.2, 0.5, 1.0, 1.5, 2.0 at. %) alloys were prepared in a vacuum induction melting furnace using the micro-submicron double-scale yttrium oxide crucible. The microstructure and interfacial reaction between the melt and crucible were charactered, and the mechanical properties of the alloy after melting were tested. The results show that the purity of the double-scale yttrium oxide crucible prepared by the slip casting method is 99%, the linear shrinkage of the crucible is 31%, and the internal pores exist in the gain of the crucible after sintering. After melting, there are no new compounds are formed on the surface of the alloy ingots, which indicates that the crucible does not react with the alloy melt. A small part of Y2O3 is dissolved into the melt, resulting in the formation of Y and O. The active alloy melt absorbs O element, and Y element can contribute to reducing the dissolution of Y2O3. The formation heat and activity coefficient of each alloy element were calculated by the Miedema model. The formation heat of Al-Y and Ti-Al is negative, while the formation heat of Ti-Y is positive. The activity coefficient of Y is the highest of all. As a result, as the Y content increases, the binding force of the Al atom increases, and the binding force of the Ti atom weakens, resulting in a decrease in the melt activity of Ti-48Al-xY alloys. The microhardness of Ti-48Al-xY alloys by the double-scale yttrium oxide crucible increases with the increase of Y content. The compressive strength of the Ti-48Al-xY alloys by the double-scale yttrium oxide crucible increases initially and decreases subsequently with the addition of Y. The total compressive strength is higher compared to the compressive strength of Ti-48Al-xY alloys by the watercooled copper crucible. Therefore, the double-scale yttrium oxide crucible is suitable for the melting of TiAl alloys.