Ga对Al-Mg-Sn合金腐蚀行为和力学性能的影响

Influence of gallium on corrosion behavior and mechanical properties of Al-Mg-Sn alloy

铝合金有着低密度、高电容量和高比强度等优良性能,广泛地应用在石油、化工、船舶等领域.纯铝表面所形成的致密氧化膜会使铝的活性降低,可通过添加Sn、Ga等元素来达到活化作用,此外,添加一定量的Mg可提高铝合金的强度.本文通过熔融铸造工艺制备了不同Ga添加量的Al-Mg-Sn合金,采用XRD、SEM、EDX等分析手段研究了其显微组织和腐蚀行为;并通过测试抗拉强度研究了Ga对铝合金力学性能的影响,还测试了其Tafel极化曲线,探究其电化学性能的变化规律.结果发现,当该铝基合金不含Ga元素时,第二相为Mg2Sn相,抗拉性能为208.7MPa,延伸率为16.3%;当Ga含量为1wt%时,富Ga相存在铝合金的晶界处,使其产生Rehbinder效应,发生韧脆性转变,抗拉性能和延伸率分别为198.8 MPa和11.1%;随着Ga含量的增加,腐蚀速率也明显加快,其原因主要是由于网状分布Mg2Sn逐渐变为弥散状,且富Ga相的存在促进了铝的活化,使其腐蚀电位发生负移.

Uminum alloy has been widely used in petroleum, chemical, shipping industry and many other fields, resulting in its mechanical properties such as low density, high capacity and high specific strength. The activity of pure aluminum is inhibited because of its conapact oxide film. Sn and Ga has been proved to improve aluminum alloys activity,and a certain Mg could enhance its strength. In this article,Al Mg Sn alloy in the effect of various Ga contents has been prepared through a melt casting n^ethod. The microstructures and corrosion behav ior of the alloys were characterized by X ray Diffraction （XRD）. Scanning Electron Micro scope（SEM） and Energy Dispersive Spectroscopy Analysis（gDS）. The tensile strength was also measured to clarify the effect of mechanical properties of gallium, and the electrocbemi cal properties were tested through Tafel curves of the alloys. The results suggest that the second phase is Mg2Sn,the ultimate tensile strength is 208.7 MPa and elongation is 16.3 when the alloy is free of gallium. The gallium exists in the aluminum grain boundary when the content of Ga is greater than 1 wt% and makes the Rehbinder effect. The alloys show a brittle transition,and the ultimate tensile strength and elongation is 198.8 MPa and 11.1 %, respectively. The corrosion rate accelerates as gallium content increases. This is mainly caused by the transition formation of the Mg2Sn phase from a network system to a dispersion system,gallium riched area also activate the aluminum alloy, consequently the open circuitpotential moved negative.