Co-free CuFeMnNi high-entropy alloy with tunable tensile properties by thermomechanical processing

An equiatomic CuFeMnNi high-entropy alloy (HEA) was synthesized and homogenized at 1000 °C to achieve a microstructure of single face centered cubic phase based on CALPHAD (CALculation of PHAse Diagrams) prediction. The strength and ductility of this Co-free (low cost) HEA can be tuned through thermomechanical processing (cold rolling and annealing at temperatures ranging from 650 °C to 950 °C). Electron backscattered diffraction, transmission electron microscopy and scanning transmission electron microscopy techniques were used to characterize the deformation microstructure of this new HEA. The results show that plastic deformation was achieved through the slip of full dislocations with Burgers vector of a/2 . No dissociated dislocations and deformation twins were observed, indicating that this alloy poses high stacking-fault energy, which is supported by first principle calculations. The research suggests that further improvement on the mechanical properties of this alloy can be achieved by reducing stacking-fault energy via alloying, providing a promising low-cost alternative to CoCrFeMnNi HEAs for engineering applications.