Microstructure and Electrochemical Properties of AlMgZnSnCuMnNi_x High Entropy Alloys

The effects of Ni content on the variation of phase structure, microstructure and electrochemical properties of AlMgZnSnCuMnNix high-entropy alloys were investigated by XRD, OM, SEM, EDS and electrochemical testing. The results showed that the alloys were composed of FCC， tetragonal and a small amount of unknown structure phases when the content of Ni was low. The tetragonal phase disappeared with the increase of Ni content. The microstructure uniformity of AlMgZnSnCuMnNi alloy was better than that of AlMgZnSnCuMn alloy. In the two kinds of alloy, each region had a variety of elements. There was no region consisted of single element. When the content of Ni was high, there was an obvious passivation range in a wide range of potential above the self-corrosion potential. The AlMgZnSnCuMnNix alloys exhibited lower self-corrosion potential. With the addition of Ni from x=0 to 1.0, the self-corrosion potential of the alloys increased gradually from -1.429 V(vs. SCE) to -1.029 V and the current density decreased from 2.41×10-4 A/cm2 to 1.13×10-5 A/cm2 correspondingly.