A D019 precipitate strengthened laser additively manufactured V and Nb bearing CoCrFeNi based high entropy alloys

Abstract

Two novel HEA compositions of [Nb¯-(FeCoNi)12]Cr3 (Nb¯ = Nb, V) were designed using a high-entropy alloying strategy by analyzing traditional IN718 superalloy based on a cluster-plus-glue-atom model. And their thin-wall-shaped bulks were prepared by laser additive manufacturing, with an emphasis on the effects of using V atoms to substitute for Nb atoms on their microstructures and mechanical properties. Also, the strengthening mechanism induced by D019 precipitates of as-aged V2Nb4 HEA was discussed. After using V to substitute for Nb, the contents of inter-dendritic C14-Laves phases are effectively inhibited. The ductility is significantly improved with a small sacrifice of strength (i.e., σb ∼ 851 MPa and δ ∼ 16.8 % for V2Nb4 HEA). After aging treatment, the main microstructure transforms from fine dendrites to recrystallized equiaxed grains. The intercrossed needle-shaped D019 precipitates with a volume fraction of 7.2 % are uniformly distributed in the FCC matrix, which hinders the dislocation slip. Thereto, the as-96-hr-aged V2Nb4 HEA exhibits the most excellent strength-ductility trade-off (e.g., σs ∼ 721.5 MPa, σb ∼ 979.5 MPa with a sufficient δ of 7.5 %). The above findings provide references for the development of LAM high-performance HEAs originating from traditional alloys.