腐蝕環境對航空用7050鋁合金金屬疲勞擧動之影響

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邵冠璋(Guan-Jhang Shao) 查詢紙本館藏

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機械工程學系

論文名稱

腐蝕環境對航空用7050鋁合金金屬疲勞擧動之影響
(Influence of corrosion environment on fatigue behavior of aerospace 7050 aluminium alloy)

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摘要(中)

本研究主要以航空用7050鋁合金為實驗材料，探討在不同腐蝕環境條件下(浸泡式腐蝕與開放式腐蝕)所呈現之疲勞裂縫成長特性，以及觀察環境變化對於疲勞裂縫成長加速性的影響。
實驗中藉由改變材料熱處理參數、腐蝕環境參數、頻率參數、應力集中因子振幅參數、加入腐蝕液時之裂縫長度以及R值，並配合光學顯微鏡（OM）、掃描式電子顯微鏡（SEM）、動態材料試驗機作分析，研究影響疲勞裂縫成長特性之因子，搭配合金已知的拉伸性質與應力腐蝕效應，可作為航空材料選用之重要依據。
由實驗結果得知，無論在空氣或腐蝕環境中，當R=0.1及0.8時，合金若實施470℃×24h均質化配合T73處理時，由於塑性變形區較大、裂縫成長路徑較粗糙、鈍化膜較厚，所以裂縫閉合效應較階段均質化配合階段淬水時效處理明顯，使第二階段裂縫成長速率較慢。當環境發生瞬時變化時，裂縫尖端所承受的應力集中因子振幅越大，將有助於腐蝕液進入裂縫尖端，而使疲勞裂縫成長加速性增加。

摘要(英)

A program of experimental and analytical tasks has been conducted to discuss the relationship between corrosion environment(immersion NaCl solution and open flow NaCl solution) and fatigue crack propagation（FCP）in an aluminum aerospace alloy 7050.We observe the influence of environmental change for the accelerating of crack growth rate,too.
The experiment was investigated via different heat treatments, corrosion environments, frequency, stress intensity factor range, crack length of add corrosion solution condition and load ratio. The influence of fatigue crack propagation was characterized and analyzed by using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Instron Model 8800 Testing System. The basis of airframe structural application is the result of experiment combining with tensile properties and stress corrosion cracking effect.
The result indicate that the alloys received homogenuzation-H470×24h have bigger plastic zone, more rough in crack surface and oxide debris then Step-homogenuzation (StepH) when load ratio (R) are 0.1 and 0.8. So homogenuzation-H470×24h have higher resistance to fatigue crack growth with the crack closure effect. And the accelerating of crack growth rate is changed by stress intensity factor range.

關鍵字(中)

★ 鋁合金
★ 金屬疲勞
★ 腐蝕環境
★ 7050

關鍵字(英)

★ corrosion environment
★ 7050 aluminium alloy
★ fatigue behavior

論文目次

摘要 ...........................................I
ABSTRACT ...........................................II
謝誌 ...........................................III
表目錄..........................................V
圖目錄..........................................VI
第一章緒論.........................................1
一、序言............................................1
二、理論基礎與論文回顧..............................2
2.1 7000系鋁合金之析出強化..........................2
2.2 7000系鋁合金之微結構與腐蝕性的關係..............6
2.3 腐蝕疲勞........................................7
2.4 裂縫閉合現象(crack closure).....................10
第二章本文.........................................12
一、前言............................................12
二、實驗步驟與方法..................................15
2.1 實驗材料的製備..................................15
2.2 疲勞與腐蝕疲勞試驗..............................16
2.3 破斷面之電子顯微鏡(SEM)觀察.....................18
2.4 金相及疲勞裂縫路徑之觀察........................18
三、結果與討論......................................20
3.1 T73與SQA顯微組織差異性之說明....................20
3.2 空氣中的疲勞裂縫成長特性........................21
3.3 腐蝕環境中的裂縫成長............................23
3.4 環境瞬時變化時對疲勞裂縫成長加速性之探討........27
四、結論............................................29
參考文獻............................................31

參考文獻

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指導教授

歐炳隆(Bin-Lung Ou)

審核日期

2004-7-14

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