Microstructural evolution and mechanical properties of Al0.3CoCrFeNiSix. high-entropy alloys containing coherent nanometer-scaled precipitates

In this work, Al0.3CoCrFeNiSix (x = 0, 0.2, 0.5, 0.8, 1.0 in molar ratio) high-entropy alloys (HEAs) were designed by introducing a non-metallic element Si. The microstructural evolution and its effect on the mechanical properties were discussed. The results suggested that the addition of Si promoted the transition from face-centered cubic (FCC) to body-centered cubic (BCC)/ordered BCC (B2) phases, in which the spherical Cr-rich BCC nanoparticles were coherently dispersed In the Al, Ni-rich B2 matrix. The mechanical properties were improved by adding an appropriate amount of Si. When x increased from 0 to 0.2, the tensile yield strength and ultimate tensile strength increased by 63% and 60%, respectively, while the elongation remained at 56%. The Vickers hardness enhanced from 143 HV (x = 0) to 826 HV (x = 1.0) with increasing Si content, and the specific wear rate reduced by two orders of magnitude accordingly. The strengthening mechanisms were evaluated for this series of HEAs based on the correlation between microstructure and mechanical properties.