Effect of MoO_3 addition on the microstructure and mechanical properties of Ti_2A1C prepared by reactive hot pressing

摘要

Fully dense (Ti,Mo)_2AlC/AI_2O_3 in situ composites with high purity were successfully synthesized at 1350 °C by reactive hot pressing of the Ti, Al, TiC, and MoO_3 powder mixtures. The effect of MoO_3 content on the phase composition, microstructure, and mechanical properties was investigated in detail. The introduction of the Al-MoO_3 displacement reaction into the Ti-Al-TiC system resulted in a submicron grain size and a homogeneously distributed matrix phase of (Ti,Mo)_2AlC with a secondary AI_2O_3 phase. The matrix grain size was significantly refined with increasing the AI _2O_3 content. Compared with the sample without MoO _3 addition, the addition of 13.81 wt MoO_3 (corresponding to 10 wt AI_2O_3 formation) evidently enhanced the hardness, flexural strength, and fracture toughness by 25, 69, and 146, respectively. The strengthening and toughening mechanisms for the (Ti,Mo) _2AlC/AI_2O_3 composites were also investigated.