本實驗將 Al-5wt%Zn合金在室溫下以路徑Bc經等徑轉角擠型（Equal Channel Angular Extrusion, ECAE）擠製4~16道使晶粒細化，探討材料微結構演化與機械性質之關係。並取相同條件製備超細晶4N純鋁(99.99%)比較兩者的拉伸變形行為，以了解添加Zn對超細晶Al-Zn合金拉伸變形行為的影響。
隨著ECAE擠製道次增加，Al-5wt%Zn晶粒細化，晶粒型態(morphology)趨於等軸狀，部分晶粒內部差排密度降低，擠製4~12道，高角度邊界(high angle grain boundarys, HAGBs)比例由16.4%增加到53.7%；擠製4道後硬度值幾乎維持定值；擠製12道時，Al-5wt%Zn高角邊界比例比4N純鋁高約24%。
於相同擠製道次之下，Al-5wt%Zn合金的強度大於4N 純鋁，因此添加Zn可產生固溶強化改善Al-Zn合金的強度。而在延展性方面，擠製12道的Al-5wt%Zn優於4N純鋁，比較兩者的表面變形差異，隨擠製道次增加，Al-5wt%Zn晶界滑移(Grain boundary sliding,GBS)的現象越明顯，進而提升均勻變形後的延展性。
Al-5wt%Zn合金在室溫進行strain rate jump拉伸測試，擠製道次增加，應變速率敏感值(strain rate sensitivity, m )變大，相對地均勻變形後的延展性(post-uniform elongation, PUE)也跟著提升，m值的增加可能與晶粒細化、晶界滑移有關。
Al-5wt%Zn的活化體積(activation volume, υ*)比4N純鋁小，Al-5wt%Zn活化體積約在32b3~76b3之間，4N純鋁的活化體積(υ*值)範圍在57 b3~122b3之間。推論影響超細晶Al-Zn差排移動的關鍵機制主要來自晶界處差排的生成與吸收之外還有差排在晶界處與Zn原子之間的作用。

In this work, ultrafine-grained (UFG) Al-5wt%Zn alloy was produced by equal channel angular extrusion (ECAE). The microstructure evolution during ECAE and the mechanical properties of the UFG Al-Zn alloy were investigated. In order to identify the effect of Zn in the Al-Zn alloy, pure aluminum (4N, 99.99%) was also studied for comparison. The grains of the Al-Zn alloy could be refined effectively by increasing the ECAE passes. However, as the ECAE passes increased, the microhardness increased initially but maintained constant after 4 ECAE passes. The dislocation density within grain interior was decreased gradually with increasing ECAE passes. After being processed to twelve ECAE passes, the UFG Al-Zn alloy exhibited 53.7% of the grain boundaries being high angle grain boundaries (HAGBs).
The UFG Al-5wt%Zn alloy exhibits superior tensile strength and elongation as compared with pure aluminum fabricated by the same ECAE process. Experimental results indicated that adding Zn in aluminum alloy could provide solid-solution strengthening and considerable enhancement in tensile ductility which might be related to an improved post-uniform elongation (PUE). The strain rate sensitivity (SRS) of the UFG Al-Zn alloy also increased with increasing the ECAE passes, which might be related to the fine grain size and the contribution of grain boundary sliding. The activation volume of the UFG Al-Zn alloy was in the range of 32b3~76b3, and the pure aluminum was in the range of 57b3~122b3. Because of the small value of the activation volume, it is suggested that the controlling mechanism for dislocation glide in the UFG Al-Zn alloy might be related to the generation and absorption of dislocations in grain boundary, as well as the interaction between dislocations and solute Zn atoms in the grain boundary.

論文審定書.....................................................................................................................i
致謝................................................................................................................................ii
摘要...............................................................................................................................iii
Abstract.........................................................................................................................iv
表目錄...........................................................................................................................ix
圖目錄............................................................................................................................x
一、前言........................................................................................................................1
二、文獻回顧................................................................................................................2
2-1 等徑轉角擠型(equal-channel angular extrusion,ECAE) 2
2-1-1 ECAE的發展與原理 2
2-2 影響ECAE 之製程參數 2
2-2-1 模角的影響 2
2-2-2 路徑的影響 3
2-2-3 擠製溫度的影響 5
2-3 超細晶金屬之機械性質 5
2-3-1 超細晶金屬之拉伸變形行為 5
2-3-2 超細晶金屬的強度 7
2-3-3 超細晶金屬的低延展性 8
2-3-4 超細晶金屬的應變速率敏感值(strain rate sensitivity, m) 9
2-3-5 超細晶金屬的晶界形成與特性 10
2-4 Al-Zn合金..................................................................................................11
2-4-1 Al-Zn合金之介紹 11
2-4-2 Al-Zn 合金經摩擦攪拌製程之機械性質 11
2-4-3 Al-Zn 合金經高壓扭轉法(HPT)後形成之結構 12
2-4-4 Al-15wt%Zn合金經ECAE製程之特性 13
三、研究目的..............................................................................................................15
四、實驗方法..............................................................................................................16
4-1 實驗材料 16
4-2 均質化處理 (Homogenization) 16
4-3 等徑轉角擠型 (ECAE) 16
4-4 微硬度測試 (Microhardness test) 17
4-5 X-Ray繞射分析 17
4-6 金相觀察 18
4-7 微結構分析 18
4-8 拉伸測試（tensile test） 18
4-9 電子背向散射繞射(EBSD)分析 19
五、實驗結果..............................................................................................................20
5-1 微硬度測試 20
5-2 XRD繞射分析 20
5-3 ECAE擠製後微結構觀察 20
5-3-1 Al-5wt%Zn 經路徑Bc 擠製後的微結構觀察（Y 面） 20
5-3-2 4N純鋁經路徑Bc 擠製後的微結構觀察（Y 面） 21
5-4 電子背向散射繞射(EBSD)分析 21
5-5 拉伸性質 22
5-5-1 擠製道次對拉伸性質的影響 22
5-5-2 4N純鋁、Al-5wt%Zn和Al-15wt%Zn[2]之拉伸性質比較 23
5-6 拉伸後的表面變形型態 23
5-6-1 拉伸後以OM觀察Al-5wt%Zn表面變形 23
5-6-2 拉伸後以OM觀察4N純鋁表面變形 24
5-6-3 拉伸後以SEM觀察Al-5wt%Zn表面 25
5-6-4 拉伸後以SEM觀察4N純鋁表面 25
5-6-5 Al-5wt%Zn與4N純鋁拉伸表面變形差異 26
5-7 應變速率改變(strain rate jump)測試 27
5-7-1 不同擠製道次之應變速率改變測試 27
5-7-2 不同拉伸應變量之應變速率敏感值 28
5-8 活化體積(activation volume) 29
5-8-1 不同擠製道次與應變速率之活化體積 29
5-8-2 比較Al-5wt%Zn與4N 純鋁之活化體積 30
六、討論......................................................................................................................31
6-1 Al-5wt%Zn經ECAE擠製後對變形組織的影響 31
6-2 Al-5wt%Zn經ECAE擠製後的硬度值與拉伸性質影響 32
6-4 ECAE應變量對Al-5wt%Zn應變速率敏感值與活化體積的影響 34
6-4-1 應變速率敏感值 34
6-4-2 活化體積 35
七、結論......................................................................................................................40
參考文獻......................................................................................................................41

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