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

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.