Effects of laser power on microstructures and mechanical properties of CoCrFeNiMn high entropy alloy with the addition of Y2O3 by directed energy deposition

The bulk CoCrFeNiMn high entropy alloy with the addition of Y2O3 is fabricated by directed energy deposition, and its microstructures and mechanical properties were investigated in relation to laser power. The XRD results revealed that FCC and Cr-rich precipitates were constant in all samples, regardless of laser power. Moreover, the lattice constant is maximum at 800 W laser power due to the increased Y content. The EBSD results indicated that higher laser power can coarse grain, but it is refined at 800 W due to the increased concentration of new compounds and Y2O3 in the sample. The texture strength of the sample processed at 1000 W is approximately 1.6 times greater than that observed in the 700 W process. Besides, the sample shows the minimum texture strength at 800 W, owing to the action of small grain size. Additionally, the higher laser power is beneficial to form <0 0 1> texture along the scanning direction and the building direction. The laser power has a proportional relationship to the average KAM value and low-angle grain boundary. The results of the deformation behavior suggest that the sample has excellent mechanical properties at 800 W, which exhibits ductile fracture.