Microstructure and Discharge Behavior of Mg-Al-Sn-In Anode Alloys

In this study, Mg-6% Al-1% Sn-1% In (wt%) alloy is fabricated with the conventional casting method. Then an alloy sheet with a thickness of 2 mm is obtained by hot extrusion with the extrusion ratio of 47.5: 1. After annealing at 200 degrees C, 250 degrees C or 300 degrees C, respectively, the alloy sheets are ready for further testing. Microstructures and discharge behaviors of the alloys under different conditions are investigated by morphology observation and electrochemical measurements. The Mg-Al-Sn-In alloy annealed at 200 degrees C exhibits better discharge performance because of uniform microstructure, fine grains, little crystalline defects, fine Mg17Al12 and Mg2Sn precipitates. AZ31, Mg-6% Al-1% Sn and Mg-6% Al-1% In alloys prepared by the same craft are used for comparisons. The result shows that the discharge property of the Mg-Al-Sn-In alloy with 200 degrees C annealing treatment is superior to that of other alloys. Detailed reasons of this result are revealed by polarization test, electrochemical impedance test and corroded morphology. It is shown that the simple primary battery, using the 200 degrees C annealed Mg-Al-Sn-In alloy sheets as anodes, can provide 1.527 V average voltage and its specific energy reaches 98.3 Whkg(-1). Thus, the 200 degrees C annealed Mg-Al-Sn-In alloy has the potential application value for seawater-activated battery. (C) 2017 The Electrochemical Society. All rights reserved.