Effect of Cr content on microstructure, mechanical, and corrosion properties of CoCr_xFeMnNi high-entropy alloys fabricated by selective laser melting

The method of using mixed powder for SLM in-situ alloying to prepare high entropy alloys has been verified to be feasible. In this investigation, the effect of Cr addition on microstructure uniformity, mechanical properties, and corrosion resistance of CoCr_xFeMnNi High-entropy alloy (with x = 0.4, 0.7, 1.0, 1.3 at. %) prepared by the SLM in-situ alloying technique has been thoroughly investigated. X-ray diffraction and scanning electron microscopy suggest that all CoCr_xFeMnNi HEAs samples are composed of a FCC matrix and little residual Cr particles, and all elements of the FCC matrix are evenly distributed, accompanied by a very small amount of Mn evaporation. Electrochemical corrosion tests have shown that with an increase in Cr content, the corrosion resistance of the alloy is significantly improved. The CoCr_1.3FeMnNi HEAs possess the best corrosion resistance against the attack of the Cl ion, with a corrosion rate 0.671 × 10⁻³ mm / year. Furthermore, the Cr element can significantly improve the microhardness, tensile strength, and plasticity of CoCr_xFeMnNi HEAs. The CoCr_1.3FeMnNi HEAs possess the best mechanical properties, with microhardness 217.8 HV_0.5, tensile strength 691 MPa and elongation rate 18.9%, respectively.