Microstructure, mechanical and corrosion behaviors of AlCoCuFeNi-(Cr,Ti) high entropy alloys

The equimolar AlCoCuFeNi-(Cr,Ti) high entropy alloys (HEAs) were synthesized by nonconsumable arc melting to investigate the effects of Cr and Ti on the mechanical and corrosion properties of HEAs. The results showed that as-cast AlCoCuFeNi-(Cr,Ti) HEM have a multi-phase microstructure, of which the solid-solution face-centered cubic (FCC), body-centered cubic (BCC) phases, and intermetallics can be observed. Ab initio molecular-dynamics (AIMD) simulations exhibit the existence of the preferred short-range ordering of Al-Ni, Co-Cr, Cr-Fe, and Ti-Co pairs in the AlCoCuFeNiCrTi liquid structure. The AIMD simulations are consistent with the experimental observation during solidification. The segregations and the FCC Cu-rich phase appear in the AlCoCuFeNiCrTi alloy, which is in agreement with AIMD calculations. The Cr addition to AlCoCuFeNi facilitates the formation of the BCC phases in the AlCoCuFeNiCr alloy, which can be explained by the larger SI and smaller delta values. The addition of large Ti atoms facilitates the formation of the FCC phase, which is due to the fact that Ti will easily induce the breakdown of the BCC solid-solution of the AlCoCuFeNi alloy in terms of decreasing the St value and increasing the delta value. The Cr addition improves the corrosion resistance of AlCoCuFeNi alloys. (C) 2016 Elsevier Ltd. All rights reserved.