组织结构对锌–铝–镁合金热浸镀层耐蚀性的影响

以热浸镀Zn–3.25Al–2.35Mg和Zn–2.55Al–1.47Mg钢板为研究对象,分别采用扫描电镜、X射线衍射、辉光放电光发射光谱等方法对不同合金镀层的组织结构、物相组成、表面元素分布情况进行研究。以热镀锌层钢板作为对比,利用动电位极化曲线和电化学阻抗谱研究不同热浸镀钢板的腐蚀行为。结果表明,锌–铝–镁合金镀层主要由共晶组织、富锌相以及少量富铝相组成。不同成分镀层的组织结构存在差异,Zn–2.55Al–1.47Mg合金镀层表面的共晶相含量高于Zn–3.25Al–2.35Mg镀层,且在镀层的浅表层存在明显的富Mg区域。Zn–2.55Al–1.47Mg镀层的耐蚀性优于Zn–3.25Al–2.35Mg镀层,说明随锌–铝–镁镀层中共晶组织含量增大,合金镀层的耐蚀性提高。

热浸Zn–Al–Mg–Ce合金镀层的耐腐蚀性能

在Zn–Al–Mg镀浴中添加不同质量分数的Ce元素,获得了Zn–Al–Mg–Ce合金镀层。X射线光电子能谱显示,Zn–Al–Mg–0.08Ce镀层表面主要由锌、铝、镁的氧化物组成,未发现铈的氧化物。采用浸泡腐蚀、极化曲线测量、电化学阻抗谱等方法研究其耐蚀性能时发现,Zn–Al–Mg–Ce合金镀层在5%Na Cl溶液中的自腐蚀倾向小于Zn–Al–Mg合金镀层,其极化电阻和交流阻抗增大,腐蚀电流密度减小,耐蚀性能提高。

Effect of heat treatment on microstructures and mechanical properties of Al-6Zn-2Mg-1.5Cu-0.4Er alloy

The microstructures and mechanical properties of Al-6Zn-2Mg-1.5Cu-0.4Er alloy under different treatment conditions were investigated by transmission electron microscopy （TEM） observation, and tensile properties and hardness test, respectively. The relationship between mechanical properties and microstructures of the alloys was discussed. With trace Er addition to A1-Zn-Mg-Cu alloy, Er and Al interact to form Al3Er phase, which is coherent with a（A1） matrix. The results show that Al-Zn-Mg-Cu alloy after retrogression and re-ageing （RRA） heat treatment exhibits higher tensile strength, ductility and conductivity.

Effects of minor Zn content on microstructure and corrosion properties of Al-Mg alloy

The effects of different Zn contents in Al-Mg alloy on the microstructure characterizations were observed by advanced electron microscopy and the corrosion properties were investigated by the inter-granular corrosion tests,the exfoliation corrosion tests,and the Potentiodynamic polarizaion tests.The τ phase(Mg_(32)(Al,Zn)_(49)) forms on the pre-existing Mn-rich particles and at the grain boundaries.According to the theory of binding energy,the formation of τ phase is much easier than that of β phase(Al_3Mg_2),somehow replacing β phase and reducing the possibility of β phase precipitation.This change dramatically decreases the susceptibility of corrosion.The Zn addition increases the corrosion resistance of Al-Mg alloy with an optimal value of 0.31%.When the Zn addition is increased to 0.78%,however,the corrosion resistance of alloy decreases once again but it is still better than that of the alloy without Zn addition.