The effect of annealing temperature on the microstructure, mechanical and electrochemical properties of arc-melted AlCrFeMnNi equi-atomic High entropy alloy
Khumo Masemola, A.P.I. Popoola, Nicholus Malatji
Abstract
In this work, an equiatomic AlCrFeMnNi high entropy alloy (HEA) was fabricated through an arc-melting and casting process. As-cast alloy ingot was annealed for 2 h at various temperatures to investigate the effect of heat treatment temperature on the microstructure, mechanical performance and electrochemical behaviour of the alloy. The morphology of the as-cast HEA consisted of interdendritic rich-Al + Ni BCC (B2) phase and majority dendritic matrix consisting largely of rich-Cr BCC phase. Annealing higher than 400 ℃, promoted the formation of FCC structure which increased in volume to 800 ℃. Increase in heat treatment temperature coarsened the grains leading to a decrease in hardness and increase in coefficient friction. A good combination of strength and ductility was observed when annealing was performed at 600 ℃. Anticorrosion properties were improved after annealing. However, high-temperature annealing lowered corrosion resistance due to the galvanic effect. The alloys demonstrated high corrosion rate in acidic condition.