Oxidation behavior of Ti55 alloy and TiBw/Ti55 composites and antioxidation mechanism of TiBw in composites at 960–1000°C

Abstract

The oxidation behavior of Ti55 alloy and TiBw/Ti55 composites at temperatures ranging from 960 to 1000°C was investigated by characterizing the surface and cross-section microstructure of specimens. Results showed that TiBw reinforcement accelerated the occurrence of Ti6O/Ti3O by dissolving oxygen in titanium in the starting oxidation stage, and the Ti6O/Ti3O transformed into TiO2 with the progression of oxidation. Meanwhile, TiBw reinforcement promoted the formation of (101) crystal planes to be beneficial to the growth of TiO2 twins. The cross-sectional characterization showed that the oxide layer of Ti55 alloy and TiBw/Ti55 composites from outside to inside was TiO2+Al2O3, TiO2, Ti-Sn compounds, Ti6O/Ti3O in sequence, which was confirmed by calculating the standard Gibbs free energy of the oxide nucleation. The TiBw reinforcement accelerated the occurrence of suboxides Ti6O/Ti3O by dissolving oxygen in titanium, and promoted the formation of (101) crystal planes which were beneficial to the growth of TiO2 twins. The optimal addition of TiBw induced the TiO2 twins, promoted the random orientation of oxides and refined the oxide size of the TiBw/Ti55 composites with 3.5% volume fractions of TiBw, resulting in the best resistance against oxidation.