Effect of M_0O_3 addition on the microstructure and mechanical properties of Ti_2AlC prepared by reactive hot pressing

摘要

Fully dense (Ti,Mo)_2AlC/Al_2O_3 in situ composites with high purity were successfully synthesized at 1350 ℃ 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 A1_2O_3 phase. The matrix grain size was significantly refined with increasing the A1_2O_3 content. Compared with the sample without MoO_3 addition, the addition of 13.81 wt% MoO_3 (corresponding to 10 wt% A1_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/Al_2O_3 composites were also investigated.