Influence of in-situ and ex-situ precipitations on microstructure and mechanical properties of additive manufacturing CoCrFeMnNi high-entropy alloys

Abstract CoCrFeMnNi high entropy alloys (HEAs) based composites have been synthesized by laser melting deposition (LMD). Through TiC and WC particle additions, ex-situ TiC and in-situ M23C6 precipitations are formed, respectively. The average grain size of the LMD-fabricated CoCrFeMnNi HEA is significantly reduced. With TiC and WC additions, appearing the combined effects of grain refinement and precipitation reinforcement, further to remarkably improve the tensile strength from 550 MPa to 610 MPa and 776 MPa for the HEAs, whereas the plasticity decreased from 52% to 47% and 37%, respectively. The HEAs with WC addition shows higher tensile strength, which probably results from the homogeneous distribution of the nano-scale M23C6 reinforcement precipitates and a single deformation pattern. This work provides insight into the effects of different introduction modes of reinforced phases when it comes to the mechanical properties for HEA composites.