Mechanical alloying synthesis and spark plasma sintering consolidation of CoCrFeNiAl high-entropy alloy

•BCC high-entropy solid solution is synthesized by mechanical alloying.•HEA powder is consisted of nanocrystallines with grain size of 20nm.•SPS-consolidated HEA depicts high hardness and strength.•Ultrafine particles exist and strengthen the bulk HEA. An equiatomic CoCrFeNiAl high-entropy alloy was synthesized by mechanical alloying, and phase evolutions, microstructure, thermal properties and annealing behaviors were investigated. It was found that a body-centered cubic structured solid solution with refined microstructure of 20nm in grain size could be obtained after 30h milling. As-milled powder exhibited good phase stability until 500°C, and transformed into a face-centered cubic phase above 500°C. The as-milled powder was subsequently consolidated by spark plasma sintering at 900°C. BCC phase and FCC phase coexisted in the consolidated HEA, which had excellent properties in Vickers hardness of 625HV and compressive strength of 1907MPa.