添加Ni元素对新型高强度低Cu中温铝合金钎料腐蚀性能的影响

Influence of Ni Addition on Corrosion Performance of Medium-temperature Filler Metal with Low Cu Content for Al Brazed Joints

为研究添加Ni元素对Al-10Si-15Cu合金钎料耐腐蚀性能的影响,本文采用三电极方法测量了Al-10Si-15Cu和Al-10Si-15Cu-4Ni合金钎料在0.5MNaCl盐溶液中的动电位极化曲线和交流阻抗谱,并利用XRD、SEM和EDS等技术分析腐蚀前后的表面成分和形貌。结果表明,Al-10Si-15Cu-4Ni合金中主要含有α-Al、Si相、Al2Cu相及Al3(Cu,Ni)2相。在Al-10Si-15Cu钎料合金的基础上添加4wt.%Ni后,自腐蚀电流密度icorr从10.18μA cm-2降低到3.42μA cm-2,极化电阻RP提高近3倍,合金耐腐蚀性提高,而临界点蚀电位EPit4Ni负移,ΔE(=EPit-Ecorr)变小,点蚀倾向加剧。Al-10Si-15Cu-4Ni合金钎料中部分Cu元素固溶在粗大耐腐蚀相Al3Ni2中,抑制了腐蚀相Al2Cu相的生成;同时由于Ni的添加耐腐蚀块状Si相转变为片状结构,Al2Cu相聚集,从而增大了基体α-Al的相对面积,这两个方面均有利于钎料合金的耐腐蚀性的提高。

The Influence of Ni addition on corrosion performance of Al-10Si-15Cu-4Ni filler metal was studied by measuring polarization curves and impedance spectroscopy in 0.5 M NaCl solution, X-ray diffraction （XRD）, scanning electronmicroscopy （SEM） and energy dispersive spectroscopy （EDS） techniques were used to analyze surface composition and morphology. Al-10Si-15Cu-4Ni filler metal was mainly composed of a-Al, Si, Al2Cu and Al3 （Cu, Ni）2. Electrochemical results showed that with 4 wt. % Ni addition, the corrosion resistance of the filler metal was improved, the corrosion current density i declined from 10.18 μA cm^-2 to 3.42 μA cm^-2 , and the corrosion resistance increased by nearly 3 times. But critical pitting corrosion potential EPit4Ni shifted negatively and the value of ΔE （= Epit- Ecorr ） decreased, thus pitting corrosion tendency was aggravated. Some Cu elements as solid solution in Al3 Ni2 depressed the generation of Al2Cu phase which was susceptible to corrosion, meanwhile, Ni addition made block Si phase turn into lamellar structure and Al2Cu phase assembled, which benefited corrosion resistance of the filler metal.