Obtaining strength-ductility combination in a laser additive manufactured (FeCoNi)86Al7Ti7 high-entropy alloy at cryogenic temperature
Kaiqiang Xie, Yacheng Fang, Pan Ma, Yang Hong, Shiguang Wan, Konda Gokuldoss Prashanth, Piter Gargarella, Yongkun Mu, Gang Wang, Yandong Jia
Abstract
High-entropy alloys (HEAs) are known 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 on (FeCoNi) 86 Al 7 Ti 7 HEA fabricated using powder bed fusion (PBF) studies the phase composition, microstructure, and mechanical properties at both room and cryogenic temperatures (298 K and 77 K). The PBF HEA exhibits a hierarchical microstructure with columnar grains, Ti-enriched cellular substructures entangled with high-density dislocations, and L21 nanoprecipitates, contributing to an excellent strength-ductility combination at room temperature. Notably, as the temperature decreases from 298 K to 77 K, both strength and ductility increase, with a higher yield strength of ∼1.0 GPa, ultimate tensile strength of ∼1.55 GPa, and ductility of ∼42%. Dislocation strengthening is dominant at both room and cryogenic temperatures, with dislocation slip as the primary deformation mechanism at 298 K and a combination of dislocation slips and stacking faults at 77 K.