Effects of composition and heat treatment on the microstructure evolution and mechanical behavior of lightweight refractory high-/medium-entropy alloys: a review

Lightweight refractory high-/medium-entropy alloys (LWRH/MEAs) offer low density, excellent corrosion resistance, and outstanding high-temperature mechanical properties, making them promising for aerospace, transportation, energy, and defense applications. However, achieving a strength–ductility synergy remains challenging. This review summarizes the relationships among alloy composition, heat treatment, microstructure, deformation mechanisms, and mechanical properties, focusing on single-phase solid solutions, multiphase structures, and precipitation-strengthened alloys, as well as TRIP and TWIP effects. Particular attention is given to locally chemically ordered B2 (LCO-B2) and ordered interstitial complex (OIC) structures as strategies for improving strength–ductility balance.