纳秒激光诱导钛合金表面着色机理及其质量评价研究

发布时间：2018-04-19 13:28

本文选题：激光着色 + 钛合金　；参考：《山东大学》2017年硕士论文

【摘要】：钛合金以其密度小、耐腐蚀性强,以及优良的热稳定性和较高的比强度等优点,目前已广泛应用于生物医学材料、机械制造、航空航天、体育用品等民用工业及国防领域。在传统激光加工技术的基础上逐渐兴起的激光着色技术,以其工艺简单、生产效率高、易实现自动化、洁净环保等优势,逐渐成为研究的热点。通过激光着色,能够提高钛合金表面的光学性能,提高钛合金的耐磨性和耐腐蚀性,并呈现出不同的色彩。为此,本文基于Nd:YAG纳秒激光器在Ti-6A1-4V钛合金表面进行着色试验,从激光参数对着色效果的影响规律、着色表面的光学属性及呈色机理、着色表面的颜色质量等方面入手,开展了以下研究工作:利用Nd:YAG纳秒激光器在钛合金表面得到了不同的颜色效果,从激光与金属相互作用的热效应出发,将钛合金表面激光着色的热作用划分为了单脉冲、线扫描和面扫描三个阶段,分别从单脉冲能量密度、脉冲重叠率和扫描重叠率三个角度分析了电流强度、扫描速度、重复频率和线间距这四个工艺参数对着色表面颜色参数(L*、a*和6*值)影响规律。利用BP神经网络,建立了电流强度、扫描速度、重复频率和线间距四个激光工艺参数与颜色参数(L*、a*和6*值)的预测模型,实现了对着色效果的有效预测,有利于指导生产实践。鉴于目前对着色表面呈色机理的解释尚未形成统一的定论,对不同扫描速度下得到的钛合金着色样本,利用分光光度计、光学轮廓仪、扫描电子显微镜和X射线能谱仪,分别从光学属性、颜色参数、微观形貌等方面进行了分析与探讨;利用构建的空气-氧化膜-钛合金基底的三层结构模型,从反射率及颜色参数两个方面分别对实验值与理论值进行了对比,两者之间的差异较小,从而可以认为不同颜色的形成是由于干涉作用引起的,最外层氧化膜的厚度不同,形成了不同的干涉效果。针对当前在着色质量评价方面没有一个统一的标准,从颜色的稳定性和均匀性两个方面对着色样本的颜色质量进行了系统的评价。借助Lab颜色空间模型,用两个颜色之间的色差值△E作为着色稳定性的评价指标,得到了各着色样本颜色稳定的激光工艺参数范围;以颜色参数(L*、a*和b*值)的标准差作为着色均匀性评价指标,利用正交试验得到了各着色样本均匀性最佳的激光工艺参数组合。
[Abstract]:Titanium alloys have been widely used in biomedical materials, mechanical manufacturing, aerospace, sporting goods and other civil industries and national defense due to their low density, strong corrosion resistance, excellent thermal stability and high specific strength.Based on the traditional laser processing technology, laser coloring technology has gradually become a hot spot for its simple technology, high production efficiency, easy to realize automation, clean environmental protection and other advantages.By laser coloring, the optical properties of titanium alloy surface can be improved, and the wear resistance and corrosion resistance of titanium alloy can be improved.In this paper, based on Nd:YAG nanosecond laser, coloring experiments are carried out on the surface of Ti-6A1-4V titanium alloy. The influence of laser parameters on the coloring effect, the optical properties and coloring mechanism of the colored surface, and the color quality of the colored surface are discussed.The following research works have been carried out: using Nd:YAG nanosecond laser to obtain different color effects on the surface of titanium alloy, the thermal effect of laser coloring on titanium alloy surface is divided into monopulse from the thermal effect of the interaction between laser and metal.The current intensity and scanning speed are analyzed from three angles of single pulse energy density, pulse overlap rate and scanning overlap rate, respectively.The effects of repetition frequency and line spacing on the color parameters of colored surface are discussed.Based on BP neural network, the prediction models of four laser process parameters, such as current intensity, scanning speed, repetition rate and line spacing, are established, which can effectively predict the coloring effect and guide the production practice.In view of the fact that the explanation of the coloring mechanism of the colored surface has not yet reached a unified conclusion, the chromatic samples of titanium alloys obtained at different scanning speeds are obtained by means of spectrophotometer, optical profilometer, scanning electron microscope and X-ray energy spectrometer.The optical properties, color parameters and microscopic morphology were analyzed and discussed respectively, and the three-layer structure model of air-oxide film titanium alloy substrate was used.The experimental and theoretical values are compared in terms of reflectivity and color parameters. The difference between the experimental values and the theoretical values is small. It can be concluded that the formation of different colors is caused by interference, and the thickness of the outermost oxide film is different.Different interference effects are formed.In view of the lack of a unified standard in the evaluation of coloring quality at present, the color quality of coloring samples is systematically evaluated from the aspects of color stability and uniformity.With the help of Lab color space model, the color difference value E between two colors is used as the evaluation index of coloring stability, and the laser process parameters range of color stability of each coloring sample is obtained.Based on the standard deviation of color parameters (L * and b *) as the evaluation index of coloring uniformity, the best combination of laser process parameters for the uniformity of coloring samples was obtained by orthogonal test.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG177;TN249

【相似文献】