Microstructure, Mechanical Properties, Corrosion Resistance and Mechanism Analysis of AlZnMgCuMn High-Entropy Alloy

The study aims to investigate the heat treatment process of light high-entropy alloy AlZnMgCuMn and its effects on microstructure, mechanical properties and corrosion resistance. The microstructure of this alloy was characterized by XRD, SEM and EDS. The mechanical properties were evaluated by electronic universal testing machine and Vickers hardness tester. The corrosion resistance and mechanism were analyzed by potentiodynamic polarization test, impedance spectrum test, CLSM and AFM. The results show that AlZnMgCuMn alloy is composed of Al-Mn quasicrystalline phase and hcp phase and the former shows dendrite morphology, while the latter is distributed between dendrites. The effects of heat treatment on the morphology, distribution and volume fraction of the two phases are small. The compression fracture strength, fracture strain and Vickers hardness of as-cast AlZnMgCuMn are 415 MPa, 4.4% and 4519.7 MPa, respectively. The E-corr and I-corr of as-cast alloy are - 726.344 mV and 1.882 mu A/cm(2), respectively. After electrochemical corrosion, obvious corrosion pittings are formed on the surface of alloy, the depth of which is about 11.8 mu m. The dendritic Al-Mn phase has a lower potential as an anode and is preferred to be corroded. As the corrosion intensifies, the corrosion microdomains are connected with each other and develop into a large corrosion area.