Annealing strategy for enhancing the fracture toughness of MoSiBTiC alloys

An optimal annealing process for enhancing the room-temperature fracture toughness of MoSiBTiC alloys was investigated in this study. The alloy with a composition of Mo-5Si-10B-10Ti-10C (at%) was subjected to three annealing conditions to control its microstructure. Quantitative microstructural analysis and mechanical testing revealed that the toughness of the MoSiBTiC alloys increased with the size of the Mo_ss phase and decreased with its hardness. Annealing at 1800 °C for 24 h promoted microstructural coarsening but also led to increased solution hardening and reduced ductility of the Mo_ss phase. In contrast, annealing at 1600 °C for 100 h improved the ductility of the Mo_ss phase by reducing solution hardening, although the coarsening of the Mo_ss phase was relatively slow. Based on these findings, a two-step annealing process that combines the benefits of lower-temperature and higher-temperature annealing conditions was proposed to effectively enhance the fracture toughness of MoSiBTiC alloys.