Anodization of Magnesium-Aluminum Alloys

摘要 本論文以AZ31B和AZ91D鎂合金為基材，針對由氫氧化鉀（Potassium Hydroxide, KOH）、氟化鉀（Potassium Fluoride, KF）、磷酸三鈉（Trisodium Phosphate, Na3PO4）、硝酸鋁（Aluminum Nitrate, Al(NO3)3）組成的各種電解液，來探討個別離子對鎂板陽極處理行為的影響。 在室溫下以定電流1A/dm2，進行10分鐘陽極處理。實驗結果顯示，氟離子的添加會在反應初始產生一層緻密的陽極膜，經過不斷的介電崩潰（Breakdown）及火花放電（Sparking）使陽極膜不斷增厚；添加磷酸根離子會使陽極膜增厚，而添加鋁酸根離子後，會使電壓上升時間拉長，相對電壓更高，陽極膜膜厚更均勻。TEM的試片分析，未火花放電的陽極膜，內部陽極膜鬆散，外層較緻密；發生火花放電的陽極膜為雙層結構，中間夾帶孔洞。低掠角XRD結果顯示，未火花放電的試片，主要是氫氧化鎂（Magnesium Hydroxide, Mg(OH)2）；發生火花放電的試片則以氧化鎂（Magnesium Oxide, MgO）為主要組成。TEM的EDX分析發現陽極膜內層氟離子的含量較外層含量多，有可能為MgF2。 關鍵字：陽極處理；鎂合金；火花放電Abstract AZ31B and AZ91D magnesium alloys were anodized using the direct current with current density of 1 A/dm2 for 10 min. in the solutions composed of potassium hydroxide, potassium fluoride, trisodium phosphate and aluminum nitrate at room temperature. Experimental results indicate that addition of resulted in the formation of dense MgF2, as shown by the TEM/EDS analysis on cross-sectional TEM specimen. This dense MgF2 film caused an increase in anodic voltage. Subsequent dielectric breakdown and sparking led to the formation of a relatively thick anodic film. Adding to the solution also promoted the growth of the anodic film. The presence of in the solution resulted in a delay in reaching a voltage plateau at a higher value, and brought about a more uniform anodic film. The anodic film formed without sparking consisted of a porous inner layer contacting the substrate and a relatively dense overlay, as revealed by cross-sectional TEM. The anodic film formed after sparking also contained two layers with microvoids residing at the interface between the two layers. Finally, glancing-angle XRD showed the anodic film form with and without sparking was mainly composed of MgO and Mg(OH)2, respectively. Key word:Anodization;Magnesium alloys:Sparking總目錄 致謝………………………………………………………………………i 摘要………………………………………………………………………ii 英文摘要………………………………………………………………...iii 總目錄…………………………………………………………...………iv 圖目錄………………………………………………………...…….......vii 表目錄………………………………………………………………….xv 第一章 前言……………………………………………………………..1 第二章 文獻回顧…………………………………………………..……5 2.1 鎂合金…………………………………………………….……5 2.1.1鎂合金之來源與製備…………………………..………….5 2.1.2鎂合金分類與鎂金屬的用途………………………………6 2.1.3鎂合金的特性………………………………………………9 2.2鎂合金之表面處理……………………………………….……12 2.2.1表面預處理………………………………….……………12 2.2.1.1 機械清洗………………………………………….…12 2.2.1.2 化學清洗…………………………………….………15 2.2.2 化成皮膜處理……………………………………………16 2.2.2.1. 鉻酸鹽皮膜處理……………………………………16 2.2.2.2. 非鉻酸鹽皮膜處理…………………………………17 2.2.3 陽極處理 ………………………………………………..18 2.2.3.1酸性陽極處理電解液…………..……………….……19 2.2.3.2鹼性陽極處理電解液………………………..….……20 2.2.4電鍍處理/無電鍍處理……………………………….……23 2.2.5表面改質…………………………………………………..24 2.3 鎂合金的未來展望………………………………………...…25 第三章 實驗方法………………………………………………………27 3.1材料製備……………………………………………………… 27 3.2實驗流程…………………………………………………..…...30 3.3 試片前處理………………………………………………...…30 3.4陽極處理.………………………………………………………30 3.5皮膜厚度量測與結構分析……………………………………33 3.5.1 膜厚度量測…………..……………………………………33 3.5.2 陽極皮膜微結構分析……………………………………..33 第四章 結果與討論……………………………………………………38 4.1鎂合金AZ31B陽極處理………………………..……………..38 4.1.1 KOH電解液………………………………………………..38 4.1.2 KOH+Na3PO4電解液………………………………………45 4.1.3 KOH+KF電解液……………………………………...……52 4.1.4 KOH+KF+Na3PO4電解液…………………………………60 4.1.5 KOH+KF+Na3PO4+Al(NO3)3電解液……………………...67 4.2 鎂合金AZ91D陽極處理……………………………………..74 4.2.1 KOH電解液………………………………………………..74 4.2.2 KOH+Na3PO4電解液………………………………………79 4.2.3 KOH+KF電解液…………………………………………...83 4.2.4 KOH+KF+Na3PO4電解液…………………………………87 4.2.5 KOH+KF+Na3PO4+Al(NO3)3電解液……………………...92 第五章 討論……………………………………………………………96 5.1火花放電對陽極膜結構的影響…………………………….96 5.2 AZ91D島狀陽極膜生成機構………………………...……100 5.3 F-效應……………………………………………………….102 5.4 PO4-3和AlO2-效應…………………………………..………103 5.5 電位比較………………………………………………...…103 第六章 結論………………………………………………………..…105 第七章 未來展望…………………………………………………..…107 參考文獻………………………………………………………………10