第二相Mg_3Hg对Mg-5%Hg-1%Ga合金电化学性能的影响

Influences of Secondary Phase Mg_3Hg Compound on the Electrochemical Properties of the Mg-5%Hg-1%Ga Alloys

采用熔炼铸造方法制备出Mg-5%Hg-1%Ga合金,在573～773K时效不同时间,利用X射线物相检测、扫描电镜结合能谱分析第二相Mg3Hg的形貌和分布,用交流阻抗法等电化学方法研究Mg3Hg对Mg-5%Hg-1%Ga阳极在3.5%NaCl(质量分数)溶液中电化学性能的影响。结果表明:时效时间从15min延长至200h时,Mg-5%Hg-1%Ga合金中α-Mg和Mg3Hg的共晶组织转变为α-Mg基体中弥散分布Mg3Hg颗粒,这种转变降低了浓差极化和法拉第反应中电荷传递电阻,提高电化学活性。弥散分布的Mg3Hg颗粒使Mg-5%Hg-1%Ga合金组织均匀,提高了耐腐蚀性能。

The Mg-5%Hg-1%Ga alloy was prepared by melting-casting.Aging at 573-773 K for different time were carried out to ensure the fine dispersion of Mg3Hg compounds.Scanning electron microscopy（SEM）,emission spectrometry（ESA） and X-ray diffraction（XRD） were employed to characterize the morphology and distribution of the secondary phase Ma3Hg.The electrochemical and corrosion behaviors of the alloy in 3.5wt% NaCl solution was studied by means of potentiodynamic,galvanostatic and electrochemical impedance spectroscopy（EIS） measurements.The relationship between the Mg3Hg compound and the electrochemical properties of the Mg-5%Hg-1%Ga alloy was discussed.The results demonstrate that when the aging time increases from 15 min to 200 h,the intergranular eutectic of α-Mg and Mg3Hg changes into dispersed Mg3Hg particles in α-Mg matrix.This transition increases electrochemical activity of Mg-5%Hg-1%Ga alloy due to the decreased concentration polarization and charge transfer resistance in the faradaic reaction.The electrochemical homogeneity of the microstructure increases the corrosion resistance of the Mg-5%Hg-1%Ga alloy.