Chemistry-structure-property relations in Al10Cr15(Fe3Mn)75−x(Ni)x medium-entropy alloys

The microstructure, phase behavior, mechanical properties, and corrosion properties of a series of Al10Cr15(Fe3Mn)75−x(Ni)x medium-entropy alloys (MEAs) spanning 0–20 at% Ni were studied to elucidate the chemistry-structure-property relationship of this system as a function of Ni content. This work demonstrates that from an initial BCC phase Al10Cr15(Fe3Mn)75 MEA, Ni additions of 5 and 10 at% result in the formation of ordered B2-phase precipitates due to interaction of Ni with Al, resulting in high hardness (∼475 HV). Further Ni addition to 15 at% leads to a dual-phase FCC+BCC structure, with B2 phase precipitates distributed in the BCC matrix relatively rich in Al and Ni but depleted in Cr. This dual-phase structure has a high yield strength (YS) of 600 MPa with a total elongation of 15%. Additionally, the B2 precipitates in BCC phase serve as preferential sites for corrosion in 0.6 M NaCl. Increasing Ni content to 20 at% results in lower YS of 300 MPa, but a significant improvement in ductility and corrosion resistance due to the increased FCC phase fraction. •Ni addition in AlCrFeMn stabilizes ordered B2 phase and FCC.•B2 phase present as cuboidal precipitates in BCC matrix.•B2 + BCC results in high hardness, high tensile strength.•Ni controls FCC phase fraction for ductility and corrosion resistance in 0.6 M NaCl.