【作者】 蒋艳平；

【导师】 周益春； 潘勇；

【作者基本信息】 湘潭大学 ， 材料物理与化学， 2002， 硕士

【摘要】 随着科学技术的发展，电镀技术的应用已经由装饰和防护迅速发展到功能性的应用领域。随着电镀层使用范围日益扩大与深入，人们对镀层性能也提出了越来越高的要求，因此对镀层性能的研究成为一个重要的研究课题，尤其是其力学性能。镀层中残余应力的存在是相当普遍的现象，而且对镀层的使用性能有很大的影响。薄膜中残余应力的存在可能引起薄膜的脱落与起皮，影响其使用寿命。因此对其残余应力的研究更是引起了人们的高度关注。本文对电沉积镍涂层中的残余应力和其他一些力学性能进行了研究，用波长为1.06微米的Nd：YAG脉冲激光器对试样进行了激光热冲击，探讨了激光热冲击对试样一些力学性能的影响。 本文首先介绍了本课题的研究历史背景和研究现状，对残余应力的测试方法进行了总结，叙述了我们选取本课题的依据。然后对电沉积的原理以及X射线衍射法测量残余应力的原理进行了介绍。通过改变其电镀工艺参数，制备出了不同系列的样品，同时得出工艺参数与残余应力之间的关系，并分析其残余应力的机制。为了提高镀层的性能，我们分别利用激光热冲击和真空热退火的方法对样品进行了处理，对其影响镀层中残余应力的机理进行了分析，得出了不同的激光参数对残余应力重新分布的影响，发现了如激光热冲击使涂层中的残余拉应力变为残余压应力等一些很有趣的实验现象。用扫描电镜观察了镀层的表面形貌，并用XRD图谱分析了镀层的微观结构。同时，用纳米硬度计对镀层的硬度和杨氏模量进行测量，用应变梯度理论分析了如“涂层硬度与杨氏模量与压痕深度的相关性”等一些有趣的实验现象。对激光热冲击过程中的温度场与应力场进行了有限元数值模拟计算，这些数值模拟结果与实验结果相比较，其变化趋势一致，均朝着拉应力减小的方向发展。更多还原

【Abstract】 With the development of science and technology, the applications of the electrodeposition technology have being transferred from decoration and protection to the functionally applied field. The electrodeposited coatings are widely used, the high properties of the coatings are also needed. Therefore, the study on the properties of the coating, especially the mechanical properties, is becoming a more important subject. Residual stress in the electrodeposited coating is inevitable, which has strongly effect on the properties during the service. The residual stress exits at the interface between the film and substrate, and may lead to the degradation, or delamination or completely failure of the coating. Therefore, the residual stress has attracted great interest in the research field. In the master thesis, the residual stress in the electrodeposited nickel coating on the drawn steel strip and other mechanical properties are investigated. The pulse laser beam was Nd:YAG laser with wave lenth of 1.06 JUJn and adjustable frequency. The effect of the pulse laser beam on the mechanical properties of the samples are discussed.In the Introduction, the application of nickel coating, the development of the residual stress in the electrodeposited coating and measurement methods of the residual stress are reviewed. According to nowadays aspect of the steel strip with electrodeposited nickel coating, the research of residual stress in the electrodeposited nickel coating is proposed.Firstly, the principal of electrodeposition and x-ray diffraction method to measure the residual stress were introduced. Secondly, a number of samples were prepared by adjusting the parameters, such as current density, thickness. The relationships between the residual stress and the parameters are investigated. Furthermore, the formation mechanism of the residual stress is discussed. In order to improve the properties of the coating, laser thermal shock and annealing were used toimprove the mechanical properties of the coating. The mechanism of the redistribution of the residual stress by laser thermal shock were analyzed. The microstructures and micrographs were studied by x-ray diffraction (XRD) and scanning electron microscopy (SEM). It was interesting that the residual stress after laser thermal shock had a new distridution compared to that before laser beam thermal shock. The residual tensile stress in original electrodeposited nickel coating would be changed as residual compressive stress. Nanoindenter was used to measure the Young’s modulus and hardness of the coatings. The strain gradient plasticity explained the dependence of indentation depth on hardness and Young’s modulus. The temperature field and the stress field during the laser thermal shock were simulated by finite element method (FEM). The results obtained by FEM is good agreement with the experimental results on the whole.更多还原