Effects of Intermetallic Phases on Electrochemical Properties of Seawater Activated Mg-6%Al-5%Pb Anodes Prepared by Powder Metallurgy

Abstract

The changes in intermetallic phases of Mg-6%Al-5%Pb (Mg-Al-Pb) alloys prepared by powder metallurgy and their effects on electrochemical properties were studied. The experimental results showed that Al powder and Pb powder formed coarse Mg 17 Al 12  phases (with size from 20 μm to 70 μm) and fine Mg 2 Pb phases (with the size of 100 nm scale) with Mg powder in the hot press sintering procedure. Fine Mg 2 Pb phases have strong diffusion ability to diffuse into Mg 17 Al 12  phases. Extruding promote the diffusion of Mg 2 Pb phases into Mg 17 Al 12  phases. Solution treatment reduced intermetallic phase amounts and produced a mixed microstructure which took Mg 17 Al 12  phase as matrix and contained Mg 2 Pb phases inside. Mg 2 Pb phases were homogeneously distributed in matrix of solution-treated alloy. Mg 17 Al 12  phases and gathered Mg 2 Pb phases will accumulate the Mg(OH) 2  corrosion products, which impede the subsequent discharge behavior. Homogeneously distributed Mg 2 Pb phases will fall off during discharge, which made the discharge curve more stable. The mixed microstructures have positive effect on corrosion resistance and discharge potential. Therefore, solution-treated alloy showed the most negative potential and smoothest curve during the galvanostatic discharge test. Compared with commercial AZ61 sheet, solution-treated alloy exhibit much higher anode properties in Mg/PbCl 2  battery test. Thus, the solution-treated alloy could serve as an excellent anode in seawater-activated batteries.

Keywords: Mg-Al-Pb alloys, Anode, Powder metallurgy