Microstructure and mechanical properties of (FeNiMnAlx)50Cu50 medium entropy alloy fabricated by powder metallurgy

Abstract

The recycled copper alloy powders prepared by physical method were further alloyed, and therefore four medium entropy alloys (MEAs), (Fe40Ni40Mn20)50Cu50, (Fe38Ni38Mn19Al5)50Cu50, (Fe36Ni36Mn18Al10)50Cu50 and (Fe32Ni32Mn16Al20)50Cu50were successfully prepared via mechanical alloying (MA) and spark plasma sintering (SPS). The influence of Al content on the microstructure and mechanical properties of the MEAs were systematically studied. Following 60 h of MA, the mechanical alloyed powders of the four MEAs consist of a primary supersaturated FCC solid solution along with a trace amount of WC contaminants. Following SPS, the (Fe40Ni40Mn20)50Cu50, (Fe38Ni38Mn19Al5)50Cu50 and (Fe36Ni36Mn18Al10)50Cu50 show a dual-phase structure consisting of a Cu-rich phase (FCC1) and a Fe-Ni-rich phase (FCC2), displaying a multiscale grain structure of ultrafine grains and micron grains. However, the (Fe32Ni32Mn16Al20)50Cu50 alloy shows a primary Cu-rich phase (FCC1) with a small amount of Fe-Mn rich phase (FCC2) and Ni-Al rich B2 phase. The plasticity of the four MEAs is gradually decreased, while the strength and hardness are gradually increased with the increase of Al content. The compressive yield strength, compressive strength and Vickers hardness of (Fe40Ni40Mn20)50Cu50 MEAs are 878 MPa, 1257 MPa and 248.5HV, respectively. Compared with (Fe40Ni40Mn20)50Cu50, the compressive yield strength and hardness of (Fe32Ni32Mn16Al20)50Cu50 are increased by 50.1% and 50.4%, respectively, whereas the fracture strain is decreased from 19.55% to 8.31%.

Keywords

• medium entropy alloy
• recycled copper
• mechanical alloying
• spark plasma sintering
• microstructure
• mechanical property