Cryogenic deformation mechanisms of CoCrFeNiW_0.2 high entropy alloy

High-entropy alloys (HEAs) exhibit good tradeoff between strength and ductility at cryogenic temperature, and their deformation mechanisms have aroused great research interest. Here, a non-equiatomic CoCrFeNiW_0.2 HEA strengthened by μ phase precipitates was prepared using vacuum arc melting, and its mechanical properties, microstructural evolution and deformation mechanisms were investigated systematically at room and cryogenic temperature. As the tensile temperature decreased from 298 K to 100 K, the yield strength of the HEA increased from 371 MPa to 627 MPa, combined with an elongation decreased from 33.9% to 21.5%. Dislocations slip is dominant during plastic deformation at all temperatures. Only a small amount of deformation twins can be found at 100 K, and they are suppressed by μ phase precipitates. The formation of slip bands and stacking faults contributed to enhanced work-hardening behavior. The interfaces between slip bands and matrix serve as major obstacle to block the dislocations motion, which is able to diminish the mean free path of dislocation. The results are helpful to understand the precipitates-strengthened CoCrFeNiW_0.2 HEA and expand the potential applications at cryogenic temperature.