本文選題：AZ91D鎂合金 + 鉬酸鹽轉(zhuǎn)化膜��； 參考：《西安科技大學(xué)》2016年碩士論文

【摘要】：近年來,鎂合金因比強度比剛度高、質(zhì)量輕、延展性良好和高的導(dǎo)熱性等諸多優(yōu)點,被廣泛地應(yīng)用于汽車、航空、電子等領(lǐng)域。但是鎂合金有個致命的缺點就是化學(xué)性質(zhì)太活潑,極易在各種環(huán)境中被氧化,因此開發(fā)鎂合金的防護技術(shù)對推進鎂合金的工業(yè)化發(fā)展具有十分重要的意義和應(yīng)用價值。本文以AZ91D鎂合金作為研究對象,采用正交實驗和單因素實驗,確認了鉬酸鹽轉(zhuǎn)化液體系為:鉬酸鈉(NaMoO_4)30g/L,溫度為50oC,高錳酸鉀(KMnO_4)8g/L,處理時間為40min,pH值為5.5。轉(zhuǎn)化膜表面形貌為寬裂紋與窄裂紋鑲嵌組合而成,EDS分析表明Mo、Mn含量在寬裂紋區(qū)分布多于窄裂紋區(qū);耐點滴腐蝕實驗表明轉(zhuǎn)化膜試樣比鎂基體在腐蝕液中的耐蝕時間延長近11分鐘;極化曲線和阻抗譜結(jié)果表明轉(zhuǎn)化膜的自腐蝕電流密度為1.32×10-7A/cm2,比鎂基體降低了2個數(shù)量級,極化電阻為1368.4?·cm2,是鎂基體極化電阻的7倍。在轉(zhuǎn)化膜的基礎(chǔ)上,采用化學(xué)轉(zhuǎn)化與溶膠凝膠技術(shù)相結(jié)合的工藝,在鎂合金轉(zhuǎn)化膜上制備出了雜化涂層,形成復(fù)合膜層。復(fù)合膜層的結(jié)合力達到1級,涂層表面形貌致密均勻無裂紋,腐蝕電流密度比鎂基體的降低了3個數(shù)量級,極化電阻達到3.03×104?·cm2。采用動電位極化和交流阻抗技術(shù)研究了轉(zhuǎn)化膜和復(fù)合膜在NaCl溶液中的腐蝕行為。結(jié)果表明,轉(zhuǎn)化膜和復(fù)合膜在浸泡后期都會出現(xiàn)感抗弧,表現(xiàn)出相似的電化學(xué)腐蝕行為,只是耐腐蝕的時間和程度相差較大,復(fù)合膜在3.5%NaCl溶液中的浸泡時間長達204h,而轉(zhuǎn)化膜的浸泡時間只有42h。
[Abstract]:In recent years, magnesium alloys have been widely used in automobile, aviation, electronics and other fields because of their advantages such as high specific strength and stiffness, light weight, good ductility and high thermal conductivity. However, magnesium alloy has a fatal drawback that its chemical property is too lively and it is easy to be oxidized in various environments. Therefore, the development of magnesium alloy protection technology is of great significance and application value in promoting the industrialization of magnesium alloy. In this paper, AZ91D magnesium alloy was used as the research object. The molybdate conversion solution system was confirmed as follows: NaMoO 430g / L, temperature 50oC, potassium permanganate KMnO 4g / L, treatment time 40 mins pH = 5.5. The EDS analysis shows that the Mo-Mn content in the wide crack zone is more than that in the narrow crack zone, and the surface morphology of the conversion film is a combination of wide crack and narrow crack mosaic. The corrosion resistance test showed that the corrosion resistance time of the conversion film was 11 minutes longer than that of the magnesium substrate, and the polarization curve and impedance spectrum showed that the corrosion current density of the conversion film was 1.32 脳 10 ~ (-7) A / cm ~ (2), which was two orders of magnitude lower than that of the magnesium substrate. The polarization resistance is 1368.4? cm ~ 2, which is 7 times of that of magnesium matrix. On the basis of conversion film, hybrid coating was prepared on magnesium alloy conversion film by combining chemical conversion and sol-gel technology. The bonding force of the composite film is 1, the surface morphology of the coating is compact and even without cracks, the corrosion current density is 3 orders of magnitude lower than that of the magnesium substrate, and the polarization resistance is 3.03 脳 10 4? cm 2. The corrosion behavior of conversion film and composite film in NaCl solution was studied by potentiodynamic polarization and AC impedance technique. The results showed that both the conversion film and the composite film had similar electrochemical corrosion behavior during the later period of immersion, but the time and degree of corrosion resistance varied greatly. The soaking time of the composite membrane in 3.5%NaCl solution was 204h, but that of the conversion membrane was only 42h.
【學(xué)位授予單位】：西安科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TG174.4

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