Tailoring the microstructure and mechanical property of additively manufactured AlCrCuFeNi3.0 high-entropy alloy through heat treatment

Abstract

The near-eutectic microstructures of AlCrCuFeNi3.0 high-entropy alloy (HEA) prepared by selective laser melting (SLM) are adjusted via heat treatments to achieve the desired mechanical properties. Results indicate that an abnormal phase transformation from fcc to ordered bcc (B2) occurs in the as-built AlCrCuFeNi3.0 HEA solution annealed at 700–900 °C, alternating fine near-eutectic lamellar structures consisting of FeCr-rich fcc and AlCu-rich B2 phases are formed at 900 °C. Such near-eutectic lamellar structures are almost maintained until 1000 °C, which makes them a promising material for high-temperature applications. The abnormal mechanical behavior of this alloy after solution annealing at 1100 °C is discovered and explained. After solution annealing at 900 °C for 1 h and aging at 500 °C for 6 h, the coarsened Cr-rich bcc precipitates in the B2 lamellae are well refined, and massive lenticular or acicular ordered fcc (L12) nano-phases coherently precipitate out on the {111} crystal plane of fcc matrix. Meanwhile, the compressive strength (∼ 2952.5 MPa) and fracture strain (∼ 45.2%) reach the desired combination. The outstanding mechanical properties benefit from the contributions of the regularly fine lamellar structures and coherent nano-precipitates. This study provides novel insights into the preparation of AlCrCuFeNi3.0 near-eutectic HEA with tailorable microstructures and outstanding mechanical properties through a combination of the SLM process and subsequent heat treatment.