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Title: | 雙極脈衝電參數及電解液成分對7075鋁合金微弧氧化膜層性質之影響 Effects of Bipolar Pulsed Electrical Parameters and Electrolyte Compositions on the Micro-Arc Oxidation Coatings on 7075 Aluminum Alloy |
Authors: | Ting-Yi Wang 王婷儀 |
Advisor: | 林新智 |
Keyword: | 7075鋁合金,微弧氧化,微觀結構,抗蝕性,耐磨耗性, 7075 aluminum alloy,Micro-arc oxidation,Microstructure,Corrosion resistance,Wear resistance, |
Publication Year : | 2018 |
Degree: | 碩士 |
Abstract: | 鋁合金因其質量輕、高比強度、價格便宜、成型性佳、優良的導電及導熱性質、可回收利用等特性常應用於民生、3C產品上,若能提升鋁合金的抗腐蝕性與耐磨耗性將使鋁合金更廣泛用於汽車、船舶與航太工業等嚴苛之環境。
微弧氧化為一種電化學表面改質技術其特色是施以高電壓在鋁合金表面形成一氧化膜,此氧化膜相較於一般陽極處理或硬質陽極處理有較高之膜層硬度以及較佳之附著性、抗蝕性與耐磨耗性。 本研究以鋁合金7075作為基材分別使用鋁酸鈉和偏矽酸鈉基礎之電解液探討在不同電參數下對微弧氧化膜層性質之影響。本實驗利用掃描式電子顯微鏡、X光繞射儀、電子探針微分析儀觀察與分析膜層之微觀形貌、化學成分和結晶組成;使用維氏硬度測試膜層之硬度並利用磨耗試驗機評估膜層耐磨耗性;透過電化學極化曲線來評估膜層抗腐蝕性。 研究結果顯示微弧氧化製程中之陰極電流密度與占空比增加能提升膜層緻密性且擁有厚度較後之膜層,因此在相同電解液系統中其膜層耐磨耗與抗腐蝕性質亦愈佳。在鋁酸鈉系統中隨著陰極電流密度增加可觀察到膜層表面鬆餅組織變少取而代之的是許多小孔洞密集分布在膜層表面,表面變得較平坦且表面粗糙度變小。經由XRD結果分析,鋁酸鈉系統中膜層主要是由α-Al2O3與γ-Al2O3組成;而偏矽酸鈉系統膜層主要是由γ-Al2O3以及少量的α-Al2O3、Mullite與非晶相所組成,因此鋁酸鈉系統其膜層硬度值可達1300~1500 HV且耐磨耗性質比偏矽酸鈉系統佳。 Aluminum alloys are widely used in a variety of industries nowadays for their high strength-to-weight ratio, good formability, low density and recyclability. However, the applications of aluminum alloys are restricted by their poor corrosion and wear resistance properties. Micro arc oxidation (MAO) essentially combines electrochemical oxidation with a high voltage spark which is applied to obtain hard oxide coatings on aluminum alloys. The coatings formed during the MAO process are superior to anodic oxide coatings on plenty properties, such as excellent adhesion to the substrate, high thickness, hardness, corrosion and wear resistance. This study investigated the effects of electrical parameters and electrolyte compositions on the structures and properties of the coating. The MAO coatings on 7075 Al alloys were obtained in aluminate-based and silicate-based electrolytes by using a bipolar pulsed power supply. The morphology, microstructure and compositions of the MAO coatings were characterized by using Scanning electron microscope (SEM), X-ray diffraction (XRD), electron probe micro-analyzer (EPMA). Furthermore, the measurements of microhardness, corrosion- and wear- resistance were also conducted. Experimental results showed that with increasing cathodic current and duty ratio, the MAO coatings become more compact and thicker, which significantly improve the wear- and corrosion- resistance. The microstructural observations of the aluminate-based coatings revealed that with increasing cathodic current, the presence of pancake-like structure is significantly reduced and a lot of small pores appear on the top of the coatings, meaning the coatings became smoother. Moreover, the aluminate-based coatings are mainly composed of α-Al2O3 and γ-Al2O3, the silicate-based coatings mainly consist of γ-Al2O3 and a small amount of α-Al2O3, mullite and amorphous phase. Due to the phase compositions, the microhardness of the aluminate-based coatings can reach 1300~1500 HV and exhibit better wear resistance than silicate-based coatings. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/79107 |
DOI: | 10.6342/NTU201802857 |
Fulltext Rights: | 有償授權 |
metadata.dc.date.embargo-lift: | 2023-08-21 |
Appears in Collections: | 材料科學與工程學系 |
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ntu-107-R05527052-1.pdf Restricted Access | 7.74 MB | Adobe PDF |
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