Mechanical Properties of Constituent Phases and Interfaces in a MoSiBTiC Alloy as Determined by Nanoindentation

Microstructure strongly governs the macroscopic mechanical response of Mo–Si–B–TiC (MoSiBTiC) alloys, yet the local constitutive and fracture properties of the constituent phases and interfaces remain insufficiently quantified. Here, we determine the room-temperature elastoplastic parameters of individual phases in a MoSiBTiC alloy by combining nanoindentation with an inverse analysis of load–displacement curves. In addition, pop-in events observed during nanoindentation into brittle phases and across interfaces are analyzed using an energy-based approach to estimate a nanoindentation-derived local fracture resistance. The Mo solid-solution phase exhibits a yield stress of ~0.63 GPa, consistent with strengthening associated with grain refinement and solid-solution hardening effects. The pop-in-based fracture resistance of the T2, TiC, and Mo2C phases falls within literature ranges reported for the corresponding monolithic materials, supporting the applicability of the method to this alloy system. Notably, TiC shows the highest fracture resistance among the brittle phases, whereas ductile–brittle interfaces exhibit markedly lower interfacial fracture resistance than brittle–brittle interfaces, consistent with severe mechanical incompatibility and stress concentration that promote interfacial debonding.