Fe3Cr2CoCuNiAlx high-entropy alloys with high damping capacity and high mechanical properties

Alloys with exceptional vibration absorption properties and strong mechanical features are crucial for various applications. This study investigates the impact of altering the aluminum molar ratio on the phase constituent, microstructure, tensile properties, and damping properties of Fe3Cr2CoCuNiAlx (x = 0.25, 0.5, 0.75, 1.0, and 1.25) HEAs. The findings demonstrate that changing the aluminum molar ratio significantly affects the volume percents of FCC and BCC phases, grain size, and overall microstructural characteristics of the alloys. Particularly, the Al0.75 HEA, featuring a primary BCC structure and the highest volume percent of secondary FCC phase with the smallest grain size, exhibits optimal damping properties with an internal friction Q-1 value of 0.061. This material also exhibits relatively high mechanical properties with the tensile strength of 768 MPa and a plastic deformation of 8.87%. The exceptional energy absorption capabilities of the alloy stem from ferromagnetic damping and interface-related damping effects. Furthermore, the BCC phase has a good tensile strength, and the presence of the FCC phase can improve the toughness. By adjusting the volume fraction of the FCC phase and the BCC phase, the strength and ductility of the HEAs can be optimally balanced between FCC/BCC phases.