摘要钛合金由于具有优异的耐腐蚀性能和生物相溶性而广泛地应用于海洋舰船和生 物医疗器械。然而，钛合金在耐磨性，可焊性，硬度低等缺陷，需要对其表面进行 合金化改性。鉴于此，本文以阳极氧化多孔钛为研究对象，以多孔钛作为基体来电 沉积纳米功能镀层，试图通过添加稀土 CeO2 纳米颗粒来改善电沉积纳米晶 Ni 镀层 的组织结构与力学性能，重点研究添加纳米 CeO2 颗粒前后对双脉冲电沉积 Ni 镀层 在沉积机理、微观结构和力学性能等方面的影响。借助 FE-SEM、纳米压痕等测试手 段对纯镍和 Ni-CeO2 复合镀层的组织结构和力学性能进行对比研究，以揭示稀土 CeO2 纳米复合颗粒的作用行为以及相关增强机理。80940

采用 FE-SEM 及 XRD 等测试手段对比研究添加纳米 CeO2 纳米颗粒对纳米晶 Ni 镀层组织结构的影响。研究结果发现：纳米 CeO2 颗粒吸附在晶界微孔等高能缺 陷区，不仅改变了 Ni 晶生长的表面能，还起到弥散强化与微合金化等作用，能显著 提高镀层的致密度以及减小 Ni 晶粒尺寸，Ni 结晶取向也由择优性向随机多方向性 生长转变。这主要归功于稀土纳米颗粒或其微量离子可以优先吸附于择优生长的 Ni 晶尖端，并可演变成 Ni 晶催化形核的中心，可促使 Ni 晶的形核率提高，起到晶粒 细化的作用。

对电沉积镀层的力学性能进行研究，具体包括纳米压痕技术、新型“ 十字交叉” 型环形硬度压痕形貌以及摩擦磨损性能等测试。纳米压痕测试表明：在 TA2 基体表 面制备了纳米晶纯镍镀层后的弹性模量和硬度大幅提高，但 Ni-CeO2 复合镀层硬度 更高且韧性更好。同时由于稀土相弥散析出而产生了显著的微合金化与弥散强化作 用，而致使复合镀层的硬度压痕由原来规则的锥形形貌变成了不规则，且压痕边缘 明显内凹和收敛性，说明镀层硬度和韧性得到显著提高。对各试样进行球－盘式圆 周干滑动摩擦磨损性能测试，结果表明：纯镍试样表现为严重的磨粒磨损和氧化疲 劳磨损；而 Ni-CeO2 镀层试样不是单一的磨损机制，而是以微弱的磨粒磨损和粘着 磨损两者混合形式存在，这主要归功于在干摩擦过程中逐渐被裸露于接触表面的稀 土 CeO2  纳米颗粒来充当滚珠和固体润滑剂，能起到良好的减摩作用。

毕业论文关键词：钛合金；Ni-CeO2  复合镀层；组织结构；力学性能

Abstract Titanium alloys are widely used in marine vessels and bio medical devices because of its excellent corrosion resistance and biocompatibility。Due to poor performances in wear resistance, weldability, hardness and so on ， titanium alloys  need to be  modified on   its

surface。In view of this, porous titanium was used as the research object and the substrate for the deposition of nano functional coatings in this paper,and this ariticle attempts to improve the microstructure and tissue properties of nanocrystalline Ni coatings by adding rare earth CeO2 nanoparticles。Moreover, structural transformation and propertiesof electrodeposited Ni coatings within and without the addition of CeO2 nanoparticels were studied。For organizational structure and mechanical properties of pure nickel and the Ni-CeO2 coatings, the reinforcing mechanisms by CeO2 addiiton and key issues were discussed in detail。

The effect of adding nano CeO2 particles on the microstructure of nanocrystalline Ni coating was studied by means of FE-SEM and XRD tests。Research results found that surface features of Ni grains were rounded by the addition of ultrasonic oscillations and then turned from irregular diamond into the elliptical shape, also emerging the persified directions for Ni growth。This was mainly attributed to that coarse grains were pided into smaller-sized ones by ultrasonic oscillations, thereby modifying surface free energy and achieving more crystal nucleus sites for better recrystallization and structural integrity。