Novel as-cast NiAlCoFeNb dual-phase high-entropy alloys with high hardness

Abstract

The microstructure, phase constitution and microhardness of Ni20Al20Co20Fe20Nb20, Ni25Al25Co20Fe20Nb10 and Ni30Al30Co20Fe15Nb5 high-entropy alloys (HEAs) synthesized by vacuum arc melting have been investigated. These as-cast HEAs have a dual-phase structure including intermetallic NiAl-rich B2 phase and FeNb-rich hexagonal Laves phase, and the Nb increase leads to more fraction of Laves phase. Ultrahigh hardness of ∼ 818 HV was achieved in the equiatomic Ni20Al20Co20Fe20Nb20 dual-phase HEA, which is consisted of 61.8 vol% Laves phase and 38.2 vol% B2 phase.