Effect of the anodization on high tempreture oxidation behavior and mechanical properties of TiAl alloy

TiAl alloy was electrochemically anodized in ethylene glycol electrolyte containing with NH4F to prepare anodic film. The influence of anodization treatment on the oxidation behavior and mechanical properties of the anodized TiAl alloy were then characterized. Results shown that based on the halogen effect a continuous and dense Al2O3 oxide scale will generate on the anodized TiAl alloy after high temperature oxidation. After oxidation at 1000 ℃ for 100 h, the weight gain of the anodized TiAl alloy was dramatically decreased from 85.86 mg/cm2 to 0.67 mg/cm2. Moreover, it is shown that the surface hardness and elastic modulus of the anodized TiAl alloy decreased first and then increased with the prolonging of oxidation time. Meanwhile, the friction coefficient of the anodized TiAl alloy increased comparing to the bare TiAl alloy. The surface wear resistance of the anodized TiAl alloy exhibited similar phenomena. This is because that during high temperature oxidation process, aluminum fluorides selectively transport to the surface through pores or micro-cracks, and are oxidized to Al2O3 at the surface region. The influence of anodization treatment on the mechanical properties of the anodized TiAl alloy is attributed to the Al2O3 content contained in the oxide scale.