微观组织对复合钎焊铝材耐蚀性能的影响

Effects of Microstructure on Corrosion Resistance of Brazing Aluminum Composite Sheets

目前,针对复合钎焊铝材钎焊前后的组织结构演变有较多研究,但针对组织与耐腐蚀性能之间的关系以及如何改善耐腐蚀性能的相关研究却报道甚少。采用循环酸性海水试验(SWAAT)盐雾腐蚀和电化学腐蚀中的极化曲线、电化学阻抗谱等方法,结合电子探针(EPMA)和能谱仪(EDS)等手段,研究了芯材再结晶组织对复合钎焊铝材耐腐蚀性能的影响。结果表明:在钎焊过程中皮材发生熔化,低熔点Al-Si共晶相沿晶界由皮材向芯材渗入,同时合金元素在皮材及其与芯材交界处发生富集;皮材表面粗大的Al-Si共晶相组织与铝基体间形成腐蚀微电池,引发晶间腐蚀并延伸至芯材内部;钎焊后形成长条状再结晶组织的试样由于扩散的高速通道减少,阻碍Al-Si相渗入及芯材合金元素在皮材晶界的富集行为,降低晶间腐蚀倾向,材料的耐腐蚀性能较好。

The influence of core materials＇ recrystallization structure on corrosion resistance of brazing aluminum composite was studied by sea water acetic acid test （SWAAT） and measurement of polarization curves and electrochemical impedance spectroscopy （EIS） , combining with means of electron probe microanalysis （EPMA） and energy spectrum analysis （EDS）. Results showed that the sheath was melted during braze welding process, and the low-melting-point Al-Si eutectic phase infiltrated into the core alloy from sheaths. Meanwhile, the alloying elements gathered at interface of core alloy and sheath. Thus, the Al- Si eutectic phases and aluminum matrix could constitute a great number of small corrosion cells, leading to intergranular corrosion along the grain boundaries and deep into the core. Furthermore, the specimens with band microstructures, which could hinder the inleakage of Al-Si phases and the accumulation of alloying elements, had lower sensitivity to intergrauular corrosion and better corrosion resistance.