Adjustable damping properties of the AlCrFe2Nix medium entropy alloys by tuning phase constituent

The effects of Ni content on the phase constituent, mechanical properties and damping capacity of the AlCrFe2Nix (x = 1.0, 1.5, 1.7, 2.1, 2.2 and 2.3) medium entropy alloys (MEAs) were studied. When x = 2.1, the microstructure of the MEA consists of BCC phase as the matrix and FCC phase as the second phase with the corresponding volume fractions of 87.7, 12.3 vol%, respectively. The combination of hard BCC matrix and soft FCC secondary phase, especially, the BCC phase is isolated by the circular FCC phase, results in a very high damping capacity up to 0.06936 for the AlCrFe2Ni2.1 MEA at the corresponding strain amplitude of 2.55 x 10-4. Both the BCC matrix and the peculiar microstructure play a key role in increasing the damping capacity of the AlCrFe2Ni2.1 MEA. Excellent damping performance and comprehensive tensile properties of AlCrFe2Ni2.1 MEA indicate that it has potential applications as the candidate of damping materials.