Enhancing strength-ductility synergy in Co-free AlCrFe2Ni2.1 multi-principal element alloy via thermo-mechanical processing

Abstract

The AlCrFeNi multi-principal element alloys (MPEAs) without Co exhibit unique microstructures and present an excellent performance-to-cost ratio. Although compositional design has received significant attention, research on processing methods remains limited. Therefore, this study revealed the influence of annealing treatment at 700 ℃, 800 ℃, and 900 ℃ for 1 hour on the microstructure and mechanical properties of cold-rolled AlCrFe₂Ni_2.1 MPEA with 60% reduction. The result indicated that the phase constitutions of the annealed alloy remained relatively unchanged compared with the as-cast and cold-rolled states, primarily consisting of the FCC, BCC, and B2 phases. However, with the increasing annealing temperature, the cold-rolled sample underwent recovery and recrystallization, evolving from a stripe-like structure to an equiaxed-grain structure. Notably, the alloy annealed at 900 ℃ for 1 hour demonstrated outstanding mechanical properties, with its yield strength increasing from 691 MPa to 940 MPa and its ultimate tensile strength rising from 1062 MPa to 1283 MPa. Additionally, ductility significantly improved, with the total elongation increasing from 10.1% to 17.2%, attributed to the variations in phase proportion. This study provides a necessary paradigm to improve the mechanical behaviors of cost-effective AlCrFeNi-based alloys through tailoring the phase structure and constitutions by thermo-mechanical processing.