Low‐energy semi‐coherent interfaces deliver strength‐plasticity synergy and softening resistance in a lightweight refractory high‐entropy alloy

Abstract Lightweight refractory high‐entropy alloys (LRHEAs) show significant promise for high‐temperature structural applications, yet often exhibit limited room‐temperature deformability and insufficient high‐temperature strength. In this study, we address these challenges by engineering low‐energy semi‐coherent interfaces between the body‐centered cubic (BCC) solid solution matrix and C14 intermetallics in the TiZrNbV 0.6 Al 0.75 LRHEA (density = 5.5 g cm −3 ). These interfaces provide exceptional dislocation accommodation capability, while the C14 intermetallics contribute 679 ± 57 MPa precipitation strengthening, resulting in a remarkable specific yield strength of ~ 282 MPa cm 3 g −1 with 27.5% plasticity at room temperature. The semi‐coherent interfaces exhibit outstanding thermal stability at 1073 and 1173 K, preserving the C14 morphology, effectively impeding dislocation motion and grain boundary migration. This stability enables exceptional high‐temperature strength retention: 1305 ± 12 MPa (84% of room‐temperature strength) at 1073 K (0.6 T m ) and 1062 ± 15 MPa (68% of room‐temperature strength) at 1173 K (0.65 T m ). This work establishes a novel LRHEA design paradigm that synergistically integrates strength, plasticity, and softening resistance across both ambient and high‐temperature regimes.