Effects of tungsten additions on the microstructure and mechanical properties of CoCrNi medium entropy alloys

• DOI: 10.1016/j.jallcom.2019.03.235
• Publication Date: 2019-03-18T12:30:50Z
• Authors: Ruobin Chang; Wei Fang; Xi Bai; Chaoqun Xia; Xin Zhang; Haoyang Yu; Baoxi Liu; Fuxing Yin
• Keywords: 02 engineering and technology; 0210 nano-technology

Abstract W element has a much higher atomic radius and Young's modulus than that of Co, Cr and Ni elements. In this work, the effects of W additions on recrystallized behaviors, mechanical properties and plastic deformation of CoCrNi medium entropy alloy are investigated. The results indicate recrystallized behaviors of alloys are retarded as the increase of W content. The activation energy of (CoCrNi)97W3 alloy dramatically increases (393.3 kJ/mol), indicating slow grain coarsening kinetics. For completely recrystallized alloys annealed at 900 °C with low W content (1 at. %), grain boundary hardening is the predominant reason for the yield strength increment compared with the CoCrNi alloy, but for alloys with high W content (3 at. %), the solid solution hardening and grain boundary hardening have the same contributions on the yield strength increment (∼120 MPa). The lattice friction stress and Hall-Petch slope of (CoCrNi)97W3 alloy are 291 MPa and 487 MPa μm−0.5, respectively. Overall, 3 at. % W additions improve yield strength of CoCrNi alloy by ∼33%, and maintain high ductility and work hardening ability.