AlZr2 phase evolution and mechanical properties regulation driven by segregation elimination during heat treatment of a novel refractory high-entropy alloy

To address the need for lightweight, high-strength materials for advanced high-temperature structures, a novel Al 0.5 Mo 0.5 NbTi 1.25 V 0.5 Zr 0.7 B 0.3 refractory high-entropy alloy (RHEA) was designed and fabricated. Its segregation-induced phase evolution during homogenization and the related mechanical response were systematically studied. Microstructural evolution proceeds through segregation-driven precipitation and subsequent dissolution, governed by competing thermodynamic and kinetic factors. At 1100 °C, diffusion kinetics dominate; prolonged holding promotes AlZr 2 precipitation along grain boundaries and refines matrix grains. At 1200 °C, thermodynamics become dominant, and extended holding dissolves grain-boundary AlZr 2 , causing grain coarsening. AlZr 2 raised high-temperature strength but lowered room-temperature ductility. The alloy homogenized at 1200 °C/12 h shows a better balance of properties, with a room-temperature yield strength of 1506 MPa and a plastic strain of 13.8%. At 800 and 1000 °C, appropriate grain-boundary AlZr 2 pins boundaries and suppresses grain-boundary sliding, giving specific yield strengths of 172.4 and 43.9 MPa cm 3 g −1 , respectively. These values exceed those of most reported lightweight superalloys and high-entropy alloys. The aging response further supports a heat-treatment strategy for synergistically optimizing room and high temperature properties in Al- and Zr-containing RHEAs.