本文選題：激光著色 + 鈦合金��； 參考：《山東大學》2017年碩士論文

【摘要】：鈦合金以其密度小、耐腐蝕性強,以及優(yōu)良的熱穩(wěn)定性和較高的比強度等優(yōu)點,目前已廣泛應用于生物醫(yī)學材料、機械制造、航空航天、體育用品等民用工業(yè)及國防領域。在傳統(tǒng)激光加工技術的基礎上逐漸興起的激光著色技術,以其工藝簡單、生產(chǎn)效率高、易實現(xiàn)自動化、潔凈環(huán)保等優(yōu)勢,逐漸成為研究的熱點。通過激光著色,能夠提高鈦合金表面的光學性能,提高鈦合金的耐磨性和耐腐蝕性,并呈現(xiàn)出不同的色彩。為此,本文基于Nd:YAG納秒激光器在Ti-6A1-4V鈦合金表面進行著色試驗,從激光參數(shù)對著色效果的影響規(guī)律、著色表面的光學屬性及呈色機理、著色表面的顏色質(zhì)量等方面入手,開展了以下研究工作:利用Nd:YAG納秒激光器在鈦合金表面得到了不同的顏色效果,從激光與金屬相互作用的熱效應出發(fā),將鈦合金表面激光著色的熱作用劃分為了單脈沖、線掃描和面掃描三個階段,分別從單脈沖能量密度、脈沖重疊率和掃描重疊率三個角度分析了電流強度、掃描速度、重復頻率和線間距這四個工藝參數(shù)對著色表面顏色參數(shù)(L*、a*和6*值)影響規(guī)律。利用BP神經(jīng)網(wǎng)絡,建立了電流強度、掃描速度、重復頻率和線間距四個激光工藝參數(shù)與顏色參數(shù)(L*、a*和6*值)的預測模型,實現(xiàn)了對著色效果的有效預測,有利于指導生產(chǎn)實踐。鑒于目前對著色表面呈色機理的解釋尚未形成統(tǒng)一的定論,對不同掃描速度下得到的鈦合金著色樣本,利用分光光度計、光學輪廓儀、掃描電子顯微鏡和X射線能譜儀,分別從光學屬性、顏色參數(shù)、微觀形貌等方面進行了分析與探討;利用構(gòu)建的空氣-氧化膜-鈦合金基底的三層結(jié)構(gòu)模型,從反射率及顏色參數(shù)兩個方面分別對實驗值與理論值進行了對比,兩者之間的差異較小,從而可以認為不同顏色的形成是由于干涉作用引起的,最外層氧化膜的厚度不同,形成了不同的干涉效果。針對當前在著色質(zhì)量評價方面沒有一個統(tǒng)一的標準,從顏色的穩(wěn)定性和均勻性兩個方面對著色樣本的顏色質(zhì)量進行了系統(tǒng)的評價。借助Lab顏色空間模型,用兩個顏色之間的色差值△E作為著色穩(wěn)定性的評價指標,得到了各著色樣本顏色穩(wěn)定的激光工藝參數(shù)范圍;以顏色參數(shù)(L*、a*和b*值)的標準差作為著色均勻性評價指標,利用正交試驗得到了各著色樣本均勻性最佳的激光工藝參數(shù)組合。
[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.
【學位授予單位】：山東大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG177;TN249

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