Effect of Copper on the Oxidation Behavior of Ti–48Al–2Cr–2Nb

摘要

Titanium-aluminide intermetallic alloys are candidate materials for some components in aerospace gas-turbine engines. Oxidation resistance and suitable joining techniques are two critical factors limiting the application of these materials. Transient-liquid-phase (TLP) bonding has been used successfully to join gamma TiAl-base alloys, but results in small amounts of copper being introduced into the alloy near the joint and this change in composition can affect oxidation resistance. The results of this investigation show that large copper additions (>2 at.%) to Ti–48Al–2Nb–2Cr result in the formation of copper-rich second phases, which can degrade oxidation resistance. On the other hand, smaller amounts of copper (1–2 at.%) improve the oxidation resistance of the alloy. Fortunately, the amount of copper in the alloy after completion of a successful TLP bond is relatively low (<1 at.%), so that the oxidation resistance of a TLP joint should be at least as good as that of the base alloy.