Effect of cooling rate on microstructure and mechanical properties of Al0.3CoCrFeNi high-entropy alloy

The influence of cooling rate on the microstructure and mechanical properties of Al0.3CoCrFeNi high-entropy alloys was systematically investigated. By adjusting preparation methods and the size of the alloys, three cooling rates, ~2.5 K s−1, ~40 K s−1 and ~103 K s−1, were achieved. The alloys were monophasic and retained the FCC structure under the three cooling rates, whereas a clear refinement of the microstructure and even distribution of elements was observed with an increase in cooling rate. In addition, the hardness of the alloys increased from 132 HV to 165 HV and the yield strength increased from 300 MPa to 430 MPa when the cooling rate was increased from ~2.5 K s−1 to ~103 K s−1, amounting to 25% and 48% increases, respectively. The improvement in the hardness and strength of the Al0.3CoCrFeNi high-entropy alloys was primarily attributed to fine-grain strengthening.