Effect of annealing treatment on microstructural evolution and compressive behavior of Al0.5CrFeNi2.5Si0.25 high-entropy alloy

Dual or multi-phase high-entropy alloys (HEAs) with nano-precipitates are of great importance to overcome the strength-ductility tradeoff of structural materials. In this work, Al0.5CrFeNi2.5Si0.25 HEAs were designed and fabricated using vacuum induction melting. The microstructure, phase evolution and compressive behavior of Al0.5CrFeNi2.5Si0.25 HEAs before and after annealing at various temperatures (750 °C, 850 °C, 1050 °C, and 1200 °C) were investigated. The as-casted and annealed Al0.5CrFeNi2.5Si0.25 HEAs constitute a dual-phase (FCC and BCC) composition with L12 and σ phases. With increasing annealing temperature (750 °C–1200 °C), the proportion of the BCC matrix containing Cr-rich nanoparticles and strip-shaped σ phases gradually increased. The Cr-rich nanoparticles were gradually refined. Partial σ phase dissolved after heat treatment at 1050 °C and 1200 °C. The variation of the precipitated phases at different temperatures led to the occurrence of strengthening, which makes the alloys overcome the tradeoff between compressive strength and ductility. Under the 750 °C–1200 °C annealing, the compressive strength increased from 2288 MPa to 2584 MPa, accompanied by an increase in fracture strain from 14.9% to 23.4%.