Oxidation Behavior of Au-55 mol%Ti High Temperature Shape Memory Alloy during Heating in Ar-50 vol%O2 Environment

Oxidation behavior and subsequent phase decomposition of Au-55mol%Ti high temperature shape memory alloy are investigated for heating oxidation up to 1773K in Ar-50 vol%O2 using a simultaneous thermogravimetry combined with differential scanning calorimetry (TGDSC). Au-55mol%Ti powder specimen begins to be oxidized at 802K and the oxidation reaction is most active at 1150K. Since the oxidation start temperature is comparable to the martensitic transformation temperatures, the oxidation must be a problem for practical high-temperature long-term applications. An equilibrium phase reaction appears near 1346K which is melting of Au produced by the reaction of AuTi + O2 1⁄4 Au + TiO2. The oxidation reaction and products assessed by the TG-DSC measurement are in good agreement with those obtained by X-ray diffraction analysis. [doi:10.2320/matertrans.M2014468]