Cooling rate-dependent microstructure and mechanical properties of Al_xSi_0.2CrFeCoNiCu_1−xhigh entropy alloys

The influence of cooling rate on microstructure and mechanical properties of the Al_xSi_0.2CrFeCoNiCu_1−xhigh entropy alloys (HEAs) were investigated. The alloys were prepared by arc melting (the I_xalloys) and injection casting assisted by liquid nitrogen (the R_xalloys). Both the phase structure of I_xand R_xalloys evolved from FCC to FCC + BCC dual-phase, and finally to a BCC phase with an increase in the Al content, and the microstructure transformed from columnar dendrite to equiaxed grain correspondingly. The x range of the R_xalloys with dual-phase structure is smaller than that of the I_xalloys. The R_xalloys also exhibited smaller grain size and spinodal decomposition plate than the I_xalloys. Additionally, because of the microstructure refinement and/or phase structure change, both the hardness and yield stress of R_xalloys were higher than the I_xalloys. The maximum increase rate presented when x = 0.6, and the minimum one presented when x = 0.4.