Abstract: The conventional strategy of strengthening nickel-based composites by maximizing carbide content faces a fundamental limitation, where excessive carbides inevitably agglomerate and coarsen, leading to diminishing strengthening returns and a severe loss of ductility. This study establishes a homogeneous carbide dispersion, not nominal content, as the determinant of superior mechanical properties. To realize this, we introduce Si as a self-consuming microstructural modulator during spark plasma sintering of a Ni20Cr-based composite. The semiconducting nature of Si markedly intensifies localized Joule heating at particle interfaces, inducing transient melting of the Ni matrix. This melting, in turn, intensifies thermal gradients and Marangoni convection, thereby facilitating the inward transport and homogenization of in situ formed nano-TiC dispersions. Remarkably, Si completely dissolves into the matrix post-sintering, avoiding the formation of brittle phases and thereby preserving ductility. The optimized composite, with only 4 wt % Ti₃SiC₂ and 3 wt % Si, achieves an exceptional yield strength of 1273 MPa, an ultimate tensile strength of 1558 MPa, and maintains good elongation. This work thus establishes a new paradigm wherein microstructural homogeneity, rather than nominal content, governs the strengthening potential of carbide-reinforced composites.

Key words: Carbide distribution, Microstructural homogenization, Strength paradigm, Si microstructural modulator, Spark plasma sintering