Microstructure Evolution and Tensile Property of a CuMnFeCoNi High-Entropy Alloy During Thermomechanical Treatment

The CrMnFeCoNi high-entropy alloy (HEA) has attracted extensive attention due to its excellent ductility and fracture toughness. However, this kind of Cr-containing systems show a strong tendency to precipitate brittle sigma phases. Then, Cr was replaced by Cu to form an equatomic CuMnFeCoNi HEA to eliminate the sigma formation concern. To obtain uniform microstructure and superior mechanical properties, here we conducted thermomechanical processing (drop cast, homogenization, cold rolling and annealing) on this alloy and revealed the microstructure evolution and tensile properties after annealing for 1 hour at 850 °C, 900 °C, 1000 °C and 1100 °C, respectively. All HEAs show dual-phase face-centered-cubic (FCC) structures with slightly different lattice constants. Their microstructures are composed of equiaxed grains and Cu-rich precipitates. Increasing temperature leads to coarser grains and Cu-rich precipitates. As expected, the alloy after annealing at 900 °C/1 hour shows best tensile property with the yield strength of 419 MPa and elongation to fracture of 28 pct. Its superior tensile property can be ascribed to the abundant fine Cu-rich particles along grain boundaries and in intragranular regions.