熱處理對7050鋁合金應力腐蝕與含鈧鋁薄膜特性之影響研究; Effect of heat treatment on the stress corrosion cracking of AA7050 and on the characterization of Al-Sc thin films

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Title:	熱處理對7050鋁合金應力腐蝕與含鈧鋁薄膜特性之影響研究;Effect of heat treatment on the stress corrosion cracking of AA7050 and on the characterization of Al-Sc thin films
Authors:	廖學隆;Hsueh-Lung Liao
Contributors:	機械工程研究所
Keywords:	慢速率拉伸試驗（SSRT）;應力腐蝕（SCC）;7050鋁合金;自行車架;預浸泡;鋁-鈧薄膜;腐蝕;反射率;薄膜附著力;車燈;Lamp;Adhesion;Reflectivity;Corrosion;Pre-immersion;Al-Sc films;Bicycle Frame;7050 Aluminium alloy;Slow Strain Rate Testing (SSRT);Stress Corrosion Crack (SCC)
Date:	2009-07-07
Issue Date:	2009-09-21 11:57:20 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本論文的研究主題包括 (1)預浸泡對不同熱處理之7050鋁合金在鹼性鹽水中應力腐蝕的影響，以及(2)鋁-0.11wt.%鈧鍍膜特性之研究。7050鋁合金在T6、T73、RRA、OP1以及OP2等不同程序熱處理後，預浸泡在鹼性(pH=12) 3.5%NaCl水溶液中240小時，使用慢應變速率拉伸試驗(Slow Strain Rate Test, SSRT)、電化學試驗(Electrochemical Test)及化學分析電子光譜儀(ESCA)等方法，來探討7050合金表面生成物與應力腐蝕破裂(SCC)性質的關係。研究結果顯示：7050鋁合金預浸於鹼性氯化鈉腐蝕液中240小時，試片因表面生成腐蝕生成物，阻隔腐蝕液的侵蝕，因而提高其抗SCC能力，此種抗SCC能力之增強以T6最顯著，依次為RRA、OP1等熱處理。（T6 (43%) > RRA (27%) > OP1 (18%) > OP2 (14%) > T73 (11%)）。經分析此表面腐蝕生成物，主要成份為Al、Zn、Mg及Cu之氫氧化物，尤其T6試片的腐蝕生成物中，氫氧化銅之成分高於OP1試片。腐蝕生成物經ESCA分析，結果顯示：T6腐蝕生成物中由CuO組成，而OP1與RRA腐蝕生成物，則由CuO與CuCl2混合生成物；含CuCl2之腐蝕生成物，對試片抗SCC能力之提升貢獻較少。另外，以DC磁控濺鍍機製作純Al與Al-0.11wt.% Sc濺鍍膜，進行鍍膜結構與性質分析，探討其作為車燈反射鏡之可行性，就薄膜附著力、光學反射率、抗腐蝕性等特性，和傳統之工業級蒸鍍Al膜試片比較。結果顯示：Al-0.11wt.% Sc濺鍍膜，其薄膜附著力優於純鋁濺鍍膜與純鋁蒸鍍膜。AFM量測結果比較顯示：Al-Sc濺鍍膜的表面粗糙度比純鋁度膜小，試片表面平滑度較高。經鹽霧試驗與高低溫循環試驗後，Al-0.11wt.% Sc濺鍍膜試片的表面光學反射率高於純鋁濺鍍膜與純鋁蒸鍍膜。因為退火處理，容易導致純鋁薄膜表面的晶粒成長與突起(hillocks)，因而導致薄膜表面性能與其光學反射率下降；相對之下，Al-0.11wt.% Sc濺鍍膜試片在5%NaCl水溶液中，無論是否經過熱處理，都顯示有較佳的腐蝕抵抗能力。 Two topics including (1) the pre-immersion effect of heat-treated (i.e., T6, T73, RRA, OP1 and OP2) aluminum alloy 7050 on the stress corrosion cracking (SCC) in alkaline (pH=12) 3.5 wt% NaCl solution; and (2) the characterization of the Al-0.11 wt.% Sc sputtered films were concerned in this study. The effect of the pre-immersion on the SCC was investigated using slow strain rate test (SSRT) under electrochemical monitoring. The corrosion products on the specimens were analyzed through electron spectroscopy for chemical analysis (ESCA). It was found that pre-immersion enhances the SCC-resistance of the specimens, however, the enhancement varies with the type of heat treatments exerted to AA7050. The enhancement decreases in the order: T6 (43%) > RRA (27%) > OP1 (18%) > OP2 (14%) > T73 (11%). Analysis of the corrosion products revealed that they comprise elements such as Al, Zn, Mg, Cu and oxygen. Electron spectroscopy for chemical analysis (ESCA) of the corrosion product displayed that the content of copper hydroxide on T6 is stronger than on OP1 and RRA . Pre-immersion leads to the formation of CuO in the corrosion products of T6 and mixture of CuO and CuCl2 in the corrosion products of OP1 and RRA . The corrosion-resistant is much less for the mixture of CuO and CuCl2 than the monotonic the CuO. A thin film of Al-0.11wt.% Sc was prepared by sputtering and its structure, characterizations (i.e., film adhesion, optical reflectivity and anti-corrosion behavior) concerned in the use of candidature reflector for the autolamp has been investigated and compared with the traditional pure Al-film prepared by thermal evaporation. The sputtered Al-0.11wt.% Sc film reveals better adhesion than the sputtered monotonic pure Al-film and than traditional evaporated pure Al-film. Through examination by atomic force microscope (AFM), the sputtered Al-0.11wt.% Sc exhibits better flatness and smoothness than the others thus displays higher optical reflectivity due to grain refinement in the film. Under long-term illumination, the films led to grain growth and hillocks formation. This grain growth and surface degradation caused by aged illumination severely decreased the reflectivity of the films, especially for the pure Al films. The sputtered Al-0.11wt.% Sc is more corrosion-resistant than the others in 5% NaCl solution regardless whether or not aged illumination.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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