Toughening and strengthening by off-stoichiometric TiC in equilibrium with Mo solid solution

B1-type TiC compounds in equilibrium with metal solid solution phases can possess off-stoichiometry allowing them to exhibit different mechanical properties compared to those containing stoichiometric TiC, which typically decreases the toughness of the material. In this study, the fracture behavior of Mo/(Ti_0.96,Mo_0.04)C_0.67 two-phase alloys was investigated. The load-displacement curves of the Mo/(Ti_0.96,Mo_0.04)C_0.67 two-phase alloys, as measured by four-point bending tests, were similar regardless of the (Ti_0.96,Mo_0.04)C_0.67 volume fraction_, whereas the peak stress and fracture toughness increased with increasing volume fraction. These results suggest that (Ti_0.96,Mo_0.04)C_0.67 acts as both a strengthening and toughening phase. Two factors are considered to contribute to its function as a toughening phase: the presence of the Mo phase within the (Ti_0.96,Mo_0.04)C_0.67 grains, and the improvement in the deformability of (Ti,Mo)C_x itself owing to its off-stoichiometry.