ZL205A铝合金表面镀钛渗氮复合改性层研究

发布时间：2018-06-03 15:53

本文选题：ZL205A铝合金 + 第一性原理　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：本文利用钛-铝之间的互扩散,通过镀钛渗氮的改性技术在ZL205A铝合金表面制备出了高硬度高耐磨性的复合改性层。首先通过第一性原理计算热扩渗过程生成相的形成能,并通过计算原子扩散系数作为辅助,实现对镀渗复合改性层的设计。采用磁控溅射方法在铝合金表面镀钛,然后将预置钛膜的铝合金进行等离子渗氮,在其表面获得复合改性层,采用XRD、SEM、EDS对钛膜和复合改性层的相结构、形貌和成分进行分析,并对镀渗复合改性层进行了硬度表征和摩擦磨损测试。第一性原理计算结果表明,Ti-Al之间发生互扩散,且Ti的扩散系数远大于铝的扩散系数。在渗氮温度下,钛铝化合物中Al3Ti的形成能最低,最容易形成。Ti N0.3的形成能远大于Al3Ti的形成能,且结合能的绝对值很大,Ti N0.3比Al3Ti难形成,但是比Al3Ti更稳定。据此预测,钛膜较厚时,通过镀钛渗氮的方法可形成表层为Ti N0.3,中间层为Al3Ti的复合改性层。钛膜较薄时,改性层为单一的化合物Al3Ti层。通过磁控溅射的方法,在ZL205A铝合金表面成功制备出一层致密且分布均匀的α-Ti,并且存在(002)晶面择优取向,随着钛膜厚度增加,择优取向趋势增强。镀钛铝合金渗氮后表层形成了梯度多相结构的复合改性层,最外层为Ti N0.3,中间层为Al3Ti。镀钛膜厚度较薄时,改性层只有Al3Ti,无Ti N0.3生成,钛膜厚度增加,复合改性层中Ti N0.3层所占比例增加。Ti N0.3同样在(002)晶面择优取向,随钛膜厚度增加,择优取向性增强,晶粒变得均匀且致密。复合改性层显著提高了ZL205A铝合金表面的硬度。镀渗复合处理的铝合金的硬度最高达HV411,是固溶时效态铝合金硬度的4.2倍。Ti N0.3存在(002)晶面择优取向时,改性层的硬度提高。复合改性层的摩擦系数虽然提高,但是其磨损率降低。经镀渗复合工艺处理的铝合金,相比于固溶时效的铝合金,磨损率分别降低了11.84%,47.13%和50.58%,可见镀渗复合改性层显著提高了铝合金的耐磨性能。改性层的磨损机制主要为磨粒磨损,并伴随有氧化磨损。
[Abstract]:In this paper, a high hardness and wear-resistant composite layer was prepared on the surface of ZL205A aluminum alloy by titanium nitriding modification by using the interdiffusion between titanium and aluminum. First, the formation energy of the formation phase in the process of thermal diffusion is calculated by the first principle, and the design of the composite coating is realized by calculating the atomic diffusion coefficient as the assistant. Titanium was deposited on the surface of aluminum alloy by magnetron sputtering, then plasma nitriding was carried out on the aluminum alloy with pre-deposited titanium film. The composite modified layer was obtained on its surface. The phase structure, morphology and composition of the titanium film and the composite modified layer were analyzed by XRDX SEMMO-EDS. The hardness and friction wear of the composite coating were characterized. The results of first principle calculation show that the diffusion coefficient of Ti is much larger than that of Al. At nitriding temperature, the formation energy of Al3Ti is the lowest in Ti-Al compounds, and the formation energy of .TiN0.3 is much higher than that of Al3Ti, and the absolute value of binding energy is larger than that of Al3Ti, but more stable than Al3Ti. It is predicted that when the titanium film is thicker, the composite modified layer of TiN0.3 and Al3Ti can be formed by the method of titanium nitriding. When the titanium film is thin, the modified layer is a single compound Al3Ti layer. By magnetron sputtering, a dense and uniformly distributed 伪 -Ti layer was successfully prepared on the surface of ZL205A aluminum alloy, and there was a preferred orientation in the crystal plane. The preferred orientation increased with the increase of titanium film thickness. The composite modified layer with gradient multiphase structure was formed after nitriding of titanium and aluminum alloy, the outermost layer was TiN0.3, and the intermediate layer was Al3Ti. When the film thickness is thin, the modified layer is only Al _ 3Ti, no Ti _ N _ 0.3 is formed, and the titanium film thickness is increased. The proportion of Ti _ N _ (0.3) layer in the composite modified layer is increased. The orientation of Ti _ N _ (0.3) is also preferred in the crystal plane. The preferred orientation increases with the increase of titanium film thickness. The grains become uniform and dense. The surface hardness of ZL205A aluminum alloy was significantly improved by the composite modified layer. The hardness of the aluminum alloy treated by composite plating and infiltration is up to HV411, which is 4.2 times of the hardness of the solution aged aluminum alloy. The hardness of the modified layer increases when there is a preferred orientation of the crystal plane of Ti N 0.3). The friction coefficient of the composite modified layer is increased, but its wear rate is decreased. The wear rate of aluminum alloy treated by plating and infiltration composite process was reduced by 11.84% and 50.58%, respectively, compared with that of aluminum alloy treated by solid solution aging, and the wear resistance of aluminum alloy was obviously improved by the composite coating. The wear mechanism of the modified layer is mainly abrasive wear, accompanied by oxidation wear.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.44

【参考文献】