Structural Features, Mechanical Properties, and Strengthening Behavior of SiC-Doped FeNiCoCr High-Entropy Alloys

SiC-doped equiatomic FeNiCoCr high-entropy alloys (HEAs) were prepared by vacuum hot-pressure sintering. The effects of SiC doping on the microstructure and mechanical properties of the alloys were closely studied. The results indicate that once embedded, SiC reacts with Cr to form Cr7C3 with an orthorhombic crystal structure. At a SiC doping amount of less than 5 wt.%, the yield strength and hardness of the alloys is found to be increased by 8.4 and 17.0%, respectively, relative to that for the alloys without doping, and the strengthening mechanism is mainly attributed to Cr7C3 particle strengthening. As soon as the SiC-doping amount is increased to 7.5 wt.%, the yield strength and hardness of the alloy reaches values of 891 MPa and 446 HV, respectively, which is 87.6 and 85.1% higher than that obtained for alloys without doping. The compressive strain still reaches 28.5%, with a flexural strength and fracture toughness of 915 MPa and 22.2 MPa m1/2, respectively. Si-rich particles are found to form at the grain boundaries of the HEA in the SiC7.5 alloy, and these particles are not composed of SiC but amorphous SiO2. The strengthening mechanism is attributed to thermal mismatch and Orowan strengthening due to the SiO2 particles.