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Additive manufacturing (AM) offers a robust approach for the rapid fabrication of CrCoNi medium-entropy alloys (MEAs). However, the mechanical strength of additively manufactured CrCoNi MEAs remains moderate. In this study, a composite material comprising a CrCoNi MEA matrix reinforced with 4 wt% TiB₂ nanoparticles was successfully fabricated using AM techniques. The resulting composite exhibited a yield strength (σ y ) of 1020 MPa and an ultimate tensile strength (UTS) of 1262 MPa, alongside a total elongation (TE) of 4.85 %. Advanced electron microscopy and dislocation-based crystal plasticity modelling were employed to elucidate the deformation mechanisms, revealing that dislocation slip and deformation heterogeneity among individual grains are predominant. The enhancement in strength is mainly ascribed to the synergistic effects of grain boundary strengthening, dislocation strengthening, and Orowan strengthening induced by the TiB₂ nanoparticles. Conversely, the limited ductility is primarily stems from the generation of brittle phases, the localized stress concentrations, and the dislocation accumulation at grain boundaries, all of which collectively contribute to the early onset of failure cracks. This study offers important guidance for developing nanoparticle-strengthened MEA composites, underscoring the capability of additive manufacturing to modulate mechanical performance via controlled microstructural design.
Zhang et al. (Wed,) studied this question.