Lightweight Al-Nb-Ti-V-Cr High Entropy Alloys with High Hardness and Enhanced Mechanical Properties Via Doping Co

Abstract

Lightweight high entropy alloys (LHEAs) with Laves phase enhancement are effective for structural materials. The phase composition, distribution and crystal structure of Laves phase in alloys can be modified by HEAs composition, which ultimately affect their mechanical properties. CoxAlNbTiVCr (x=0, 0.5, 1, 1.5 and 2, atomic ratio %) LHEAs were designed and prepared to characterize microtopography and tailor mechanical properties. The introduction of Co transform changes the microstructure of LHEAs from a single BCC structure to the mixture dendrite structure, which is consisted of BCC phase, C14 and C15 Laves phase. Wherein the C14 and C15 Laves phase exhibit coupled growth, and several parameters are used to predict the formation of Laves phase in LHEAs. When Co is added, Laves phase volume fraction gradually increases, which leads to an enhancement in the compressive strength from 1520.8 MPa to 1844.4 MPa and to a certain extent increases the fracture strain. The improvement of mechanical properties mainly originates from solid solution strengthening and second phase strengthening. This work will provid guidance for composite design of high performance LHEAs.

Keywords: Lightweight high entropy alloy, Laves phase, Microstructure, Mechanical properties