Enhanced deformability of TiC induced by off-stoichiometry

Abstract

NaCl-type MX compounds, comprising transition metals and nonmetals, exhibit excellent mechanical and thermal properties, making them suitable for high-performance applications such as cutting tools and aerospace components. However, their ductility is limited, particularly in stoichiometric forms such as TiC. Therefore, further investigation into improvement of their deformability and overall mechanical performance using off-stoichiometry and alloying is required. This study investigates the deformation behavior and mechanical properties of off-stoichiometric TiC formed in Mo–Ti–C ternary alloys via micropillar compression and nanoindentation tests. The activation of the {111}⟨110⟩ slip system and no fracture were observed after the plastic strain exceeded 5 %, indicating enhanced deformability due to the off-stoichiometry. The maximum shear stress required to initiate plastic deformation (τ_max) was proportional to the shear modulus, a trend consistent with the ideal strength observed in various metals. This finding suggests that τ_max corresponds to the shear stress necessary for the initial nucleation of dislocations. Both the yield stress and hardness increased with increasing shear modulus, indicating that these properties are governed by the Peierls stress in the large-strain regime. Overall, the findings demonstrate that the deformation in the ductility-enhanced off-stoichiometric TiC is dominated by dislocation motion and that its strength is primarily controlled by shear modulus.