Microstructures and mechanical properties of mechanically alloyed and spark plasma sintered Al0.3CoCrFeMnNi high entropy alloy

Abstract

The present study focuses on phase evolution in Al0.3CoCrFeMnNi high entropy alloys (HEAs) during mechanical alloying and after spark plasma sintering. Aluminium addition hardens and induces ordered precipitates in a soft fcc alloy based on CoCrFeMnNi. Mechanical alloying of the alloy powders resulted in a single fcc phase. However, ordered B2 precipitates and chromium carbide precipitates were observed after spark plasma sintering. Sintering temperature optimization was done and maximum densification and hardness were obtained at 900 °C. High compressive yield strength of 979 ± 20 MPa and compressive ductility of 39 ± 3% were observed for the SPS processed alloy. Significant contributions from grain boundary strengthening coupled with dispersion strengthening via carbides and B2 particles appear to be major contributors to alloy strengthening. These hard intermetallic particles not only keep the grain growth in check but also increase the cumulative (fcc + B2) strength of the material.