Abstract Scope |
Dual-precipitation strengthening of CoCrNi medium entropy alloy (MEA) was studied in this work. To achieve this, a series of (CoCrNi)92.5–xAl7.5Ndx MEAs (x = 0, 0.1, 0.3, 0.6, 0.7) was fabricated by vacuum arc melting, homogenization, hot-rolling and annealing. With co-doping of Al and Nd in CoCrNi, HCP NdNi5 and B2 NiAl precipitates formed in the FCC CoCrNi matrix resulting in the improved strength and hardness of the alloy. Specifically, the yield strength and ultimate tensile strength of Nd-0.7 alloy reached 1025 and 1379 MPa, respectively, while they were 506 and 913 MPa for Nd-0 alloy. The hardness of the alloys increased from 245.8 HV in Nd-0 to 277.2 HV in Nd-0.7. Compared to other CoCrNi-based MEAs, both the yield strength and ultimate tensile strength in this work were enhanced significantly while the fracture strain remained at 37%, which was mainly attributed to grain refinement and precipitation strengthening. |