Microstructure evolution and enhanced mechanical properties of additively manufactured CrCoNi medium-entropy alloy composites

Abstract

High-entropy alloys (HEAs) and medium-entropy alloys (MEAs) are regarded as promising advanced material with vast potential applications because of their many functional properties. However, the lower yield strength (YS) and wear resistance of as-cast face-centered cubic (FCC) phase HEAs/MEAs restricts their wide application in industry. In this study, the microstructure evolution, crystallographic orientation, tensile properties and wear resistance of CrCoNi metal matrix composites (MMCs) with different amounts of Mo and WC particles manufactured by directed energy deposition (DED) were systematically analyzed. Microstructure observation revealed that Mo segregated at the cellular boundaries and grain refinement occurred when WC particles were added, but the intensity of< 001 > crystallographic orientation along the build direction did not change significantly. The tensile results show that the YS and ultimate tensile strength (UTS) are increased by 56.18% and 35.45% respectively without significant decrease in ductility (from 46.92% to 42.51%) when 6.5 at% Mo and 2 wt% WC were added. Meanwhile, the wear resistance of Mo6.5 + 2 wt% WC samples are increased by 7.45 times compared with the CrCoNi matrix. These findings provide a new perspective for additive manufacturing (AM) of HEAs/MEAs MMCs with excellent strength-ductility combination and wear resistance.