Powder processing of titanium aluminide having superior oxidation resistance

摘要

Ti powders and Al powders are combined to prepare a mixture of 40 DIFFERENCE 55 at % of Al and the balance of Ti. After CIP and degassing, plastic working by hot extrusion is applied to form a shaped mixture of Ti and Al. The shaped mixture is then processed by HIP to synthesize titanium aluminide while diffusing Al into the Ti structure to form an Al2O3 phase occurring from both the reaction between Al and oxygen contained in the Ti structure and the oxides on the Al surface, and to disperse the Al2O3 to form the Al2O3 protective film. With the reaction between Al and oxygen contained in the Ti structure and with the "Pegging" effect, both the Al2O3 a phase formed at the grain boundaries of crystals or in the crystal grains of titanium aluminide and the Al2O3 phase existing on the surface of raw material Al powder peg the surface Al2O3 film to the surface of the titanium aluminide body. This "Pegging" effect enhances the adhesiveness of the film and improves the oxidation resistance of titanium aluminide.