【作者】 林凯；

【导师】 李淑琴；

【作者基本信息】 南京航空航天大学 ， 材料加工工程， 2011， 硕士

【摘要】 钛合金材料凭借其优异的综合性能及良好的减重效果在航空航天领域中得到了越来越广泛的应用。但是,当钛合金与铝合金接触使用时,由于两者之间存在较大的电位差,使得钛/铝合金在腐蚀介质中会构成腐蚀电偶,加速铝合金的腐蚀,带来钛/铝合金的接触腐蚀问题。尤其是在使用钛合金紧固件紧固铝合金时,由于应力和缝隙的综合作用,铝合金的腐蚀情况更为严重。针对上述问题,本文从接触腐蚀的主要影响因素入手,首先采用热浸镀法在TC4钛合金表面制备Al-Zn合金改性层,通过减小接触电偶的电位差和高阻膜的生成增加接触使用时的接触电阻来减弱电偶腐蚀的影响。然后在实验过程中设计相应的电化学腐蚀测试、全浸试验和中性盐雾试验来对改性之后的钛/铝合金接触腐蚀防护性能进行检验。最后通过扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)等现代测试分析手段来表征改性层的组织形貌、化学成分、相组成,并对改性层的力学性能及其应用于钛/铝合金接触腐蚀防护效果进行了检测。结果表明:二浴单件溶剂法,浸镀温度为670℃,浸渗时间7min,提升速度0.1m/s,并添加质量分数为0.2%Ce工艺参数下所制备的Al-Zn改性层,满足钛/铝合金接触腐蚀防护及其力学性能的要求。改性层有效厚度达到40μm,截面组织由最外层的富Al-Zn相和中间合金层的富Ti-Al相构成,不仅能够降低TC4表面电位还能起到牺牲阳极保护阴极的作用,而且改性层组织致密、表面硬度高、结合力好,适合紧固件的接触使用。电化学腐蚀测试、全浸试验、中性盐雾试验结果都表明改性层对钛/铝合金接触偶中的铝合金起到了很好的防护作用,将接触使用的铝合金使用寿命提高2~3倍,对钛合金基体也具有一定的保护作用。更多还原

【Abstract】 Because of the good integrated mechanical properties, low density and high strength to weight ratio, titanium alloys have been widely used in the filed of aerospace and spaceflight. But when the titanium alloys contact with aluminium alloys in corrosion solutions, there will be a problem. The problem is contact corrosion which occurred by the large difference of stability potential between titanium alloys and aluminium alloys. Because of the promotion effect of stress and crevice, the contact corrosion problem will be more serious when the titanium alloy fastener is used to fasten the aluminium alloys.According to the problem, this article will start with resolve the main factor of the causations. The measure is to form a coating of Al-Zn on titanium alloys by hot-dip technology to decrease the potential difference of the contact metals to weaken the effect from galvanic corrosion. Then, designed appropriate electrochemical corrosion test, immersing corrosion test and the neutral salt-mist experimentation to test the protection effects of the Al-Zn coating on the titanium alloy. At last, the structure morphology, composition, and phase composition of the coating were analysised by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), the effect of the contact corrsion protection was also been tested by these modern methods.The results showed that: 670℃, immersing 7min, 0.1m/s out speed, add 0.2wt% of Ce is the best processing parameter for the two-bath single solvent hot-dip processing. Under the processing parameter, the coating has the best contact corrosion protection and the mechanical property of the coating can content with the contact use also. The thickness of the modified layer can reach 40μm. The layer section structure was formed by outermost layer which is rich of Al-Zn phase and middle layer which is rich of Ti-Al phase. Not only decreased the stability potential of the titanium surface but also provided protection to the cathodic metal. And the layer has compact structure, high surface hardness, good adhesion, suitable for the use of contact fastenners; the result of electrochemical corrosion test, immersing corrosion test, and the neutral salt-mist experimentation show that: the layer can give good protection to the Ti/Al alloys contact corrosion. At least it can increase the service life of aluminum alloys for 2~3 times. The coating has a protective effect to the titanium alloy substrate, and also has a certain resistance to corrosion itself.更多还原