Fabrication of CoCrFeNiMn high entropy alloy matrix composites by thermomechanical consolidation of a mechanically milled powder

CoCrFeNiMn high entropy alloy matrix composites with in-situ carbide and oxide particles were fabricated by thermomechanical consolidation of a mechanically milled powder at 1000 and 1150 °C respectively. The sample consolidated at 1000 °C exhibited a microstructure consisting of Cr-rich M23C6 carbide particles, spinel (Cr, Mn)3O4 oxide particles, ultrafine grains with an average size of 920 nm and a major 〈001〉 + minor 〈111〉 dual fiber texture. When the consolation temperature increased to 1150 °C, Cr-rich M23C6 carbide particles were dissolved and the spinel (Cr, Mn)3O4 oxide particles coarsened. These led to larger grains with an average size of 6.06 μm and allowed formation of only sharp 〈001〉 fiber texture. This microstructural variation with the increase of consolidation temperature led to a decrease of strength and improvement of ductility. Analysis of the strengthening mechanisms reveals that grain boundary strengthening and Orowan strengthening play a major role in strengthening for the high strength sample consolidated at 1000 °C, while these mechanisms contribute significantly less to the strength for the sample consolidated at 1150 °C. It was also found that the sample consolidated at 1150 °C was weakened by the 〈001〉 texture.