研究了纳米SiC颗粒强化7075铝合金(SiCp/7075Al)经T6处理后在3.5% NaCl中性水溶液中的腐蚀特性及腐蚀机理.结果表明, 适量纳米SiC颗粒的加入,可提高AA7075-T6的自腐蚀电位和击穿电位, 降低腐蚀速率, 增强其耐蚀性.SEM观察表明, SiCp/7075Al-T6的腐蚀以点蚀为主,主要发生在晶界及近晶界区域, 没有大的点蚀坑,而未经强化的AA7075-T6则呈现出严重的点蚀和晶间腐蚀的特征,这与EIS特征相符, 浸泡实验也得到了同样的结果.TEM观察证实SiC颗粒在晶界的存在分割了η相;阻断了晶界阳极性的η相与其边缘合金组成的腐蚀电偶形成的活性通道;阻碍了蚀孔的长大, 提高了腐蚀抗力.
Corrosion characteristics of AA7075 reinforced with nano-SiC particles(SiC\rm p/7075Al) after T6 treatment were studied in 3.5% NaCl solutions and the corrosion mechanisms were further analyzed. The results show that in comparison with the bare 7075Al, the free corrosion potential of SiC\rm p/7075Al become much positive and its corrosion rate decreases, therewith its corrosion resistance enhances. The surface microstructure of the sample after corrosion text and then po-lished was analyzed by SEM, two distinct features were found: (1) micropitting corrosion occorred at grain boundary and the adjacent Al matrix in the SiC\rm p/7075Al-T6; (2) The number and the spread area of pits on the AA7075-T6 are significantly larger than that on the SiC\rm p/7075Al-T6; intergranular corrosion of AA7075-T6 is very serious, which are consistent with the EIS and immersion test. The SiC\rm p distributes discontinuously on the grain boundary was observed by TEM, the η (MgZn2) phase and the active corrosion path resulting from the η phase and their adjacent Al matrix were destroyed by SiC\rmp, the corrosion resistance was then improved.
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