TiAl合金の疲労き裂発生に及ぼす微視組織と環境の影響

抄録

In this study, the effects of microstructure and high temperature exposure on fatigue crack initiation morphologies in TiAl alloys were investigated. The SPF test increasing the microstructural sensitivity at the specimen surface combined with the microstructural observation on the specimen surface was used to investigate the effect of microstructure. In addition, specimens were exposed to high temperatures under decompression and nitrogen displacement to investigate the effects of high temperature exposure environments. The experimental results showed that the crack initiation life was significantly affected by the microstructure at the crack initiation potion; particularly, the crack initiation life of the lamellar phase with the lower tensile strength was shorter than that of the other phases. The growth rate and type of oxidation scales formed on the TiAl alloy surface, as well as the effect of the microstructural phase on it, varied depending on the oxygen and nitrogen concentrations in the high temperature exposure environment and the atoms contained in each phase. The crack initiation life was significantly reduced by the oxidation scale formed during high temperature exposure; however, there were few differences in crack initiation lifetime depending on the environment.