Synchronously enhancing the strength and ductility of CrMnFeCoNi high-entropy alloy with WC addition fabricated by laser additive manufacturing

Abstract

CrMnFeCoNi high-entropy alloy (HEA) manufactured by laser powder bed fusion has been demonstrated to possess a superior trade-off of tensile strength and ductility due to unique microstructures during the printed process. However, the improvement of mechanical properties of 3D printed-CrMnFeCoNi HEA through the addition of nano-scaled ceramic particles instead of in-situ precipitated particles is poorly studied. In this work, the effects of WC additions on the microstructure evolution and strengthening mechanism of additive-manufactured HEA samples at both room temperature (298 K) and cryogenic temperature (77 K) were systematically investigated. Except for the representative hierarchical microstructure characteristics of 3D printed- HEA samples, WC particles are dissolved completely in the CrMnFeCoNi matrix without obvious element segregation. The mechanical tests at room temperature (RT) revealed an excellent comprehensive mechanical property (tensile strength of 925 MPa and ductility of 38%) of the HEA sample with 5 wt% WC addition, which is mainly attributed to the solid solution strengthening induced by WC dissolution. In addition, the strength and ductility of the HEA sample synchronously increase when the testing temperature decreases from 298 K to 77 K, due to the reaction between dislocation and high-density deformation twins (DTs). The tensile strength (∼1420 MPa) of HEA-5 wt% WC sample at 77 K is higher than that of traditional CrMnFeCoNi HEA, because of contribution to strengthening from dislocation pile-up, entanglement and wavy dislocation slide.

Keywords

• Selective laser melting
• High-entropy alloy
• Solid solution Strengthening
• Cryogenic deformation
• Deformation twins