Mechanical properties and corrosion resistance of AlxCoCuFeMn high-entropy alloys

In the engineering application of alloys as structural materials, the mechanical properties and corrosion resistance are the key factors that need to be considered, and which are closely related to the microstructure. The effects of Al on the microstructure, mechanical properties and corrosion resistance of AlxCoCuFeMn (x = 0, 0.25, 0.5, 0.75, 1) high-entropy alloys (HEAs) have been investigated in the present work. The results indicate AlxCoCuFeMn HEAs have a typical dendritic structure, the Al free CoCuFeMn HEA has a Cu-rich FCC1 phase in interdendrites region and a Fe–Co rich FCC2 phase in dendrite region. When the content of Al increases, the fraction of FCC1 phase precipitated in the dendrite region, the FCC2 phase gradually developed into BCC&B2 phases, and finally only FCC1 and BCC&B2 phases were left in AlCoCuFeMn. With increasing of Al contents, the hardness and compressive yield strength of HEAs increased monotonically from 175 HV, 434 MPa to 463 HV, 1342 MPa, respectively. Meanwhile, the mass density decreased from 7.94 g/cm3 to 6.99 g/cm3 with increasing Al contents. The corrosion resistance of HEAs are ameliorated as the Al content increased. Among the five HEAs, AlCoCuFeMn shows remarkable comprehensive corrosion resistance, for which, the Ecorr and Icorr values are found to be −0.342 V and 5.53 × 10−6 A cm−2. The results of present study are useful to design low-cost corrosion-resistant HEAs with high strength.