中文摘要：
	本研究主旨在探討不同熱處理狀態對7050鋁合金腐蝕疲勞性質之影響。比較在空氣中 與腐蝕環境中(3.5 wt% NaCl) 不同熱處理的疲勞壽命和疲勞裂縫成長的差異性。並試著了解應力腐蝕機構與疲勞機構對7050鋁合金腐蝕疲勞行為影響的程度。此外，亦利用光學顯微鏡(OM)和掃描式電子顯微鏡(SEM)，對金相組織與破斷面加以觀察分析，以瞭解裂縫的生成及成長模式。 實驗結果顯示，各種熱處理試片在腐蝕環境下之疲勞壽命與疲勞裂縫成長速率之表現 都有明顯較空氣中惡化的趨勢，此乃由於材料表面受到腐蝕液的侵蝕產生蝕孔使裂縫更容易生成，再加上腐蝕環境引起氫脆使材料脆化使得裂縫成長加速。而T73較T6熱處理在空氣中有較長的疲勞壽命，但在腐蝕環境中的疲勞壽命卻較短，主要是因為在空氣中T73裂縫成長速率較慢，而在腐蝕環境中，T73產生嚴重的孔蝕使裂縫生成較快。腐蝕疲勞裂縫成長機構為穿晶模式，而應力腐蝕裂縫成長機構則為沿晶模式，因此改善晶界雖可增加抗應力腐蝕性，但對抗腐蝕疲勞機構影響較小，且應力腐蝕的裂縫成長速率遠小於疲勞裂縫成長，所以腐蝕疲勞裂縫成長速率主要還是由疲勞機構所主導。 由SEM觀察中得知，腐蝕疲勞的起源是由腐蝕液侵蝕的蝕孔處形成，並有羽毛狀紋路由起始處向外擴散延伸，在延伸中留下海灘狀紋路，最後呈延性破壞。而在腐蝕環境中的 海灘紋為起伏較大的脆性紋路，而空氣中呈現較平滑的紋路。
Abstract：
	This study investigated the corrosion fatigue properties of 7050 aluminum alloys in different heat treatments. In particular, the fatigue life and fatigue crack growth rate in air and 3.5 wt% NaCl solution for specimens in various tempers were made a comparison. The effect of the fatigue and stress corrosion cracking mechanisms on the corrosion fatigue behavior was characterized. Fractograph and microstructure analyses with scanning electron microscoy (SEM) and optical microscoy (OM) were conducted to determine the corrosion fatigue crack initiation and propagation mode. Results showed that in all tempers both fatigue life and fatigue crack growth rate tended to be worse in corrosive environment than in air. The effect of NaCl solution facilitates the fatigue crack initiation at corrosion pits and enhances crack propagation by hydrogen embrittlement as compared to air alone. 7050 Aluminum alloy in T73 temper exhibited longer fatigue life in air but shorter fatigue life in 3.5 wt% NaCl as compared to that in T6 temper. This is attributed to the fact that fatigue crack growth rate in T73 is lower than that in T6 under air while fatigue crack initiation is easier from corrosion pits in T73 than in T6 under corrosive environment. Microstructural observations indicate that corrosion fatigue cracking is transgranular type and stress corrosion cracking is intergraular. Therefore, improvement of grain boundary characteristics by overaging treatment such as T73 to increase the stress corrosion cracking resistance did not guarantee the improvement of corrosion fatigue resistance. Fractography analyses indicate that corrosion fatigue cracks mostly initiated from corrosion pits followed by feathery river line features and striations as the cracks stably grew until final fracture. The striations observed in corrosive environment are brittle type in contrast to the ductile ones observed in air.