Obtaining Strength-Ductility Combination in a Laser Additive Manufactured (Feconi)86al7ti7 High-Entropy Alloy at Cryogenic Temperature

Abstract

High-entropy alloys (HEAs) are remowned for their distinctive microstructural features, outstanding performance, and potential applications, establishing them as novel metallic materials. Studies indicate that face-centered cubic HEAs generally offer increased strength and toughness at lower temperatures, suitable for cryogenic applications. This work prepared (FeCoNi)86Al7Ti7 HEA using powder bed fusion (PBF) and studied its phase composition, microstructure, and mechanical properties at 298K and 77K. The PBF-processed HEA exhibits a hierarchical microstructure with columnar grains, Ti-enriched cellular substructures entangled with high-density dislocations, and L21 nanoprecipitates, contributing to excellent strength-ductility combination at room temperature. Notably, as the temperature dropped from 298 K to 77 K, both strength and ductility increased, with a higher yield strength (YS) of ~1.0 GPa, ultimate tensile strength (UTS) of ~1.55 GPa, and ductility of ~42%. Dislocation strengthening is dominant at both temperatures, with dislocation slip as the primary deformation mechanism at 298 K and a combination of dislocation slips and stacking faults at 77K.

Keywords: high entropy alloy, selective laser melting, Microstructure, cryogenic mechanical property, stacking fault.