TiB粒子強化Ti合金基複合材料の破壊特性と微細構造の関係

抄録

Titanium (Ti) alloy matrix composites (TMC) attract attention as aerospace materials owing to their outstanding specific mechanical properties in compared with the conventional Ti alloys. Among the candidates of reinforcement for TMC, Titanium boride (TiB) is one of the best candidates because TiB is chemically stable in Ti matrix and does not make any intermediate layer at Ti/TiB interface. However, it has been reported that TiB reinforced Ti alloy matrix (Ti-TiB) composite has the brittle fracture behavior in previous studies, and the relationship between the microstructure and fracture properties of Ti-TiB composite has not been discussed enough. In this study, we fabricated Ti-3Al-2.5V-TiB composites by the powder metallurgy process, and revealed that the fracture toughness of Ti-3Al-2.5V-7.5vol% TiB composite was 23 MPa√m. During the fracture toughness test, Ti-3Al-2.5V-TiB composites were immediately fractured when the load achieved to the critical value to propagate the crack. The SEM micrographs of fracture surface of Ti-3Al-2.5V-TiB composites implied that the crack selectively propagated inside of TiB whiskers. Therefore, it is likely that the optimization of microstructure in Ti-3Al-2.5V-TiB composites can improve the their fracture properties.