Effect of Electromagnetic Pulses on the Microstructure and Abrasive Gas Wear Resistance of Al0.25CoCrFeNiV High Entropy Alloy

Abstract

High entropy alloys (HEAs) are among the most promising materials, owing to their vast chemical composition window and unique properties. Segregation is a well-known phenomenon during the solidification of HEAs, which negatively affects their properties. The electromagnetic pulse (EMP) is a new technique for the processing of a metal melt that can hinder segregation during solidification. In this study, the effect of an EMP on the microstructure and surface properties of Al0.25CoCrFeNiV HEA is studied. An EMP, with an amplitude of 10 kV, a leading edge of 0.1 ns, a pulse duration of 1 ns, a frequency of 1 kHz, and pulse power of 4.5 MW, was employed for melt treatment. It was found that the microstructure of Al0.25CoCrFeNiV HEA changes significantly from dendritic, for an untreated sample, to lamellar “pearlite-like”, for an EMP treated sample. Moreover, EMPs triggered the formation of a needle-like σ-phase within the solid solution grains. Finally, these microstructural and compositional changes significantly increased the microhardness of Al0.25CoCrFeNiV HEA, from 343 ± 10 HV0.3 (without the EMP) to 553 ± 15 HV0.3 (after the EMP), and improved its resistance against gas-abrasive wear. Finally, an EMP is introduced as an effective route to modify the microstructure and phase formation of cast HEAs, which, in turn, opens up broad horizons for fabricating cast samples with tailorable microstructures and improved properties.