Effects Of Composition And Thermal Deformation Of Mg-Hg-Ga Anode Material On Alloy Microstructure And Corrosion Properties

Magnesium anode material has good application prospects as an excellent anode material for seawater-activated batteries,but its electrochemical performance is unstable and current efficiency is not high due to the poor anodic polarization and corrosion resistance of magnesium anode materials.In this paper,the effects of Ga and Hg alloying element content and thermal deformation such as extrusion and rolling on the microstructure,self-corrosion properties and electrochemical properties of magnesium anode materials were studied,which provided guidance for alloy design and preparation of high-performance magnesium anode materials.The main conclusions are as follows:1.The microstructures of the four Mg-Hg-Ga alloys all includeα-Mg and Mg₅Ga₂second phases.The content of Hg element increased from 1.5%to 2.0%,which promoted the formation of the second phase Mg₅Ga₂and made the second phase obviously refined.In the as-cast Mg-2.5Ga-2Hg alloy,there are a large number of discontinuous Mg₅Ga₂phases in the grain boundaries,and homogenization,extrusion and rolling make the grain boundary second phase in the alloy into uniformly dispersed Mg₅Ga₂second phase particles,and the size is refined.2.The corrosion resistance and discharge performance of extruded Mg-Hg-Ga alloy are affected by the content of Hg and Ga elements.When the Hg content increased from 1.5%to 2%,the corrosion resistance of the Mg-Hg-Ga alloy was enhanced,and the hydrogen evolution rate decreased from 0.98 ml·cm^-2·h^-1to 0.89 ml·cm^-2·h^-1,The weight loss rate decreased from 0.96 mg·cm^-2·h^-1to 0.74 mg·cm^-2·h^-1,and the discharge voltage did not change significantly.When the Ga content is increased from 1.5%to 2.5%,the average discharge voltage of the alloy increases from 0.94 V to 1.06 V,and the specific capacity of the battery increases from 1587.3 m Ah·g^-1to 1666.7 m Ah·g^-1.The optimized Mg-2.5Ga-2Hg alloy has excellent performance,hydrogen evolution corrosion rate(0.65 ml·cm^-2·h^-1),weight loss rate(0.64·mg·cm^-2·h^-1)and corrosion current density(0.20 m A·cm^-1)was the lowest,with an average discharge voltage of 1.06 V and a specific capacity of 1666.7m Ah·g^-1.3.Extrusion can effectively reduce the self-corrosion rate of the Mg-2.5Ga-2Hg alloy.The extruded Mg-2.5Ga-2Hg alloy has the smallest hydrogen evolution corrosion rate,weight loss rate and corrosion current density,which are 0.977 ml·cm^-2·h^-1,0.638 mg·cm^-2·h^-1,0.67 m A·cm^-2,showing the best corrosion resistance,and its discharge voltage（1.05 V）,second only to the homogenized state（1.10 V）,the corrosion resistance of the as-rolled Mg-2.5Ga-2Hg alloy decreases,and the average discharge voltage drops to 0.79 V.4.The corrosion products of Mg-Hg-Ga series alloys are mainly Mg（OH）₂and contain a small amount of Mg CO₃,and the corrosion types are mainly pitting corrosion.Among them,the corrosion product film of extruded Mg-2.5Ga-2Hg is the most dense,and the corrosion is most uniform.