Multicomponent alloys: Coherent vs noncoherent precipitate strengthening

Inclusion-reinforcement has been used as a pivotal strategy in advancing the mechanical properties of metal alloys. In the framework of chemical complexity of inclusions from traditional chemically homogeneous precipitates to chemically complex multicomponent intermetallic compounds, this review outlines the structural characteristics and deformation mechanisms of concentrated multicomponent alloys compared with traditional precipitate-strengthened dilute alloys, distinguishing between coherent and noncoherent precipitate strengthening. Coherent precipitates leverage slip continuity with the matrix, simultaneously act as both dislocation sources and obstacles, resulting in a self-hardening mechanism to achieve outstanding synergy of strength-ductility. In contrast, noncoherent precipitates, in addition to acting as obstacles to dislocation glide, they induce severe stress concentrations and even interfacial cracking, causing progressive strain localization and contributing to the strength–ductility trade-off. Emphasis is placed on the matrix-precipitate-composition design of complex multicomponent alloys and the deformation mechanism-mechanical properties-strengthening mechanisms of single-phase FCC multicomponent alloys. Furthermore, the precipitate strengthening of concentrated multicomponent alloys are elaborated with a focus on both coherent and noncoherent ductile multicomponent inclusions. In spite of their advantages, this review also emphasizes the challenges, limitations, and emerging perspectives for pushing the bounds for next-generation concentrated multicomponent alloys.