【作者】 张金生；

【导师】 左禹；

【作者基本信息】 北京化工大学 ， 材料学， 2007， 博士

【摘要】 铝合金结构粘接广泛应用于航空航天、国防、交通、机械制造和其它行业。阳极氧化技术是铝合金粘接前处理的主要方法之一,铬酸和磷酸阳极氧化膜粘接接头既有很高的初始力学性能又有优异的湿热耐久性能,但关于阳极氧化前铝合金表面机械处理、脱氧活化工艺对粘接性能的影响以及阳极氧化膜结构参数与粘接性能的关系还有待进一步研究。结构粘接领域应用最广泛的铬酸阳极氧化膜除有优异的粘接性能外还有较强的耐腐蚀性能,但其高毒高污染性使其取代技术的研究成为铝合金粘接前处理研究焦点。本论文以硬铝LY12为试验材料,通过不同细度砂纸打磨考察了铝合金表面宏观粗糙度对粘接性能的影响。结果表明,在不经任何化学或电化学处理后,粗糙度适中的铝合金表面粘接性能好；粒径大的砂纸打磨后的铝合金表面,经碱蚀、磷酸阳极氧化处理后,宏观粗糙度对粘接性能的贡献仍有体现。经不同浸蚀活化工艺处理后,铝合金表面微米级形貌不同,磷酸阳极氧化处理后,这种微米级形貌仍然影响粘接性能。试验表明,硫酸盐(P2)活化和电压磷酸阳极化(LVPAA)浸蚀工艺是环境友好的、理想的铬/硫酸浸蚀替代方法。应用中性硼酸盐二次阳极氧化充孔法并配以现代表面分析仪器,深入研究了阳极氧化膜厚度、孔隙率、氧化膜胞径和孔径与粘接性能的相关性。结果表明,氧化膜的厚度对粘接性能的影响不大,过厚的氧化膜反而容易形成粘接弱界面层；氧化膜孔隙率和孔径是膜粘接性能的主要控制参数,对于具有同种结构的阳极氧化膜层,胞径是孔隙率与孔径的函数,胞径越大,粘接性能越好；采用不同的氧化电压可制备胞结构尺寸不同的膜层,因而可通过电压的优化提高膜层的粘接性能。对比分析了铬酸、磷酸和硼/硫酸阳极氧化膜粘接性能优劣的结构因素,并以此为基础开发了一种硼/硫/磷酸混酸阳极氧化技术,这种新型阳极氧化膜有较好的粘接性能与抗腐蚀性能,是一种较为理想的铝合金铬酸阳极氧化替代技术。更多还原

【Abstract】 Adhesive bonding joints of aluminum and its alloys is widely used in many fields such as aviation, aerospace, defense, automotive and so on. Anodizing is one of the important pre-treatments to aluminum alloys for structural bonding. Anodic films, which are anodized in chromic acid and phosphoric acid, have both excellent initial adhesion and better durability performance to adhesive joints. But many works need to do further, for example, the effects of macro-roughness of aluminum alloys surface, deoxidizer technique and the relationship between structure of anodic films and adhesion performance. Although chromic acid anodizing as a pre-treatments for structural bonding joints can provide both excellent adhesive properties and good resistance, harmful pollution existed in the anodic films and bath. So the study on replacement of chromic acid anodizing is becoming hot.The influence of surface macro-roughness finished by series of sandpaper on the performance of bonding joints of aluminum alloys has been studied in this paper. The experiment results show that the adhesive bonding strength of LY12aluminum alloy is influenced by the surface roughness. The samples finished with abrasive papers of moderate grade sizes have higher bonding strength, which may result from the composite effects of increased surface area and decreased mechanical interlocking effect as the surface is getting rougher. The surface finishing with abrasive papers before phosphoric acid anodizing may influence the bonding strength of samples. Finishing with a moderate grade paper before phosphoric acid anodizing shows a better bonding strength. However, no such influence is observed when alkali etching is applied between finishing and anodizing.The micro-feature of aluminum alloys surface was infected by the etched and active pretreatment. And then, adhesive performance is depend on the micro structure. Lap-shear and wedge tests showed sulphate active (P2) and low voltage phosphoric acid anodizing dipping (LVPAA) are ideal replacement of chromic-sulphuric acid (FPL) etching process which is harmful to human being and nature.With the help of re-anodizing technology and SEM, effects of thichness, porosity, cell diameter and pore diameter of anodized film on bonding performance have been studied. The results indicated film thichness has limited influence on joints’initial adhesion and durability. However, the film is too thick to make the adhesive performance decrease because of gas-filling defects formation in the interfacial region between epoxide and oxidized film. Porosity and pore diameter are key factors lead to adhesive performance undulation. In terms to PAA film, when porosity decreased and pore diameter increased, the adhesive performance enhanced. Formation voltage is key contral parameter to oxidized film structure, so the film having excellent adhesive performance can be obtained by adjustment of formation voltage.Based on relationship of structural with performance, a phosphoric acid modified boric/sulphric acid anodizing process has been developed. The film obtained by the process has excellent adhesive performance and corrosion resistance, hence the anodizing process is an ideal choice to replacement of CAA technology.更多还原