Study Of Electrochemical Properties Of As-Rolled AZ91 Magnesium Alloy

Magnesium alloy has a multitude of excellent characteristics such as active chemical properties,negative standard electrode potential,and high energy density,furthermore,compared with lithium metal,magnesium alloy has lower cost and higher safety,which is widely used in the field of chemical power and has fabulous potential for development.However,there are still a series of critical problems such as hydrogen precipitation corrosion when magnesium alloy is used as battery anode material,which significantly limits the development of magnesium batteries.AZ series magnesium alloys are widely used and developed,so this paper selects AZ91 magnesium alloy,which has better corrosion resistance and discharge activity,as the research object to investigate its electrochemical properties,to find an optimal preparation process for the anode sheet,and then improve the comprehensive performance of AZ91 magnesium alloy as anode material for magnesium batteries.Based on the idea of“plastic deformation by electropulsing treatment+adapted electrolyte”,this paper investigates the electrochemical properties of as-rolled AZ91 magnesium alloy prepared by different rolling processes before and after electropulsing treatment and in different electrolytes through a series of experimental methods such as XRD analysis,microstructure observation,immersion weight loss test,electrochemical test,and air battery test.The main research results are as follows:AZ91 magnesium alloy under different rolling deformations（0%,20%,30%,and 40%）shows varying results in the immersion weight loss test,the corrosion resistance of as-cast magnesium alloy（0%rolling deformation）is better than that of as-rolled magnesium alloy（20%,30%,and 40%rolling deformation）,which is related to the increased galvanic corrosion between magnesium substrates due to the fragmentation and dispersion of theβ-Mg₁₇Al₁₂phase in the microstructure during plastic deformation.The as-cast magnesium alloy possesses more outstanding discharge performance at low current densities（5 m A/cm²,10m A/cm²）,while the discharge performance of as-rolled magnesium alloy is superior at high current densities（40 m A/cm²,50 m A/cm²）.The second phase ofβ-Mg₁₇Al₁₂ fragmentation will increase the discharge activation point,expand the discharge active region,and enhance the discharge ability of magnesium alloy.The corrosion resistance and discharge activity of AZ91 magnesium alloy under different rolling deformations（0%,20%,30%,and 40%）are improved to different degrees after electropulsing treatment.On the one hand,the electropulsing treatment will accelerate the dissolution of theβ-Mg₁₇Al₁₂ phase;on the other hand,the high-energy grain boundary area will increase under the action of high-energy pulse current,under the influence of these two factors,the comprehensive performance of AZ91 magnesium alloy has been significantly improved.After electropulsing treatment,the as-cast magnesium alloy（0%rolling deformation）shows better corrosion resistance,while the as-rolled magnesium alloy（20%,30%,and 40%rolling deformation）manifests higher discharge activity at 5,10,40,and 50 m A/cm²current densities.AZ91 magnesium alloy under different rolling deformations（0%,20%,30%,and 40%）is more sensitive to Cl^-and Mg²⁺in KCl,Mg Cl₂,and Mg SO₄ solutions.The discharge activity of as-cast（0%rolling deformation）and as-rolled magnesium alloys（20%,30%,and 40%rolling deformation）boosted with increasing Cl^-concentration;the corrosion resistance of as-cast and as-rolled magnesium alloys strengthened with increasing Mg²⁺concentration,which is related to the stronger aggressiveness of Cl^-and the easy formation of Mg（OH）₂on the alloy surface by Mg²⁺.In addition,it is still the as-cast magnesium alloy that has the most striking corrosion resistance for the same electrolyte and electrolyte concentration.It is also found that magnesium alloy has a short discharge time and low discharge voltage in Mg Cl₂ and Mg SO₄ solutions,thus these two solutions are not suitable as electrolytes for magnesium batteries,and the discharge activity in Na Cl and KCl solutions can be maintained at a high level.Through the above study,it is found that the corrosion resistance and discharge activity of the as-rolled AZ91 magnesium alloy after electropulsing treatment are optimal in Na Cl and KCl solutions at 30%and 40%rolling deformation,and possesses the most outstanding overall performance when used as an anode material for magnesium batteries.