本實驗將Al-15wt%Zn及Al-5wt%Zn合金經等徑轉角擠型(Equal Channel Angular Extrusion)以模角120°擠製16道次得到超細晶，探討擠製溫度及路徑對材料微結構和機械性質的影響。
隨著擠製溫度增加，Al-15wt%Zn平均晶粒尺寸變大，晶粒內部差排密度降低，比較100 °C及200 °C擠製結果，高角度晶界由67%下降至26%，硬度則從74.8 Hv下降至49 Hv，由增加溫度提升材料回復速率造成材料內部差排相消機率增加可以合理解釋這些結果。
比較路徑Bc與路徑C擠製後微結構的差異，在路徑Bc中，晶粒形狀幾乎成等軸狀，高角度晶界平均分布於晶粒間，而在路徑C中晶粒呈現長軸狀，其長軸平行於ECAE擠製中之剪變帶，高角度晶界較少且集中分布於平行長軸方向。
提升擠製溫度，由於晶粒細化的結果，降低Al-15wt%Zn的強度，但晶界特性的差異造成延展性大幅增加。而改變擠製路徑則對材料的強度沒有太大影響，主要的差異在最大抗拉強度後的非均勻伸長率部分，受材料的應變速率敏感值不同所影響。

Ultrafine-grained (UFG) Al-15wt%Zn and Al-5wt%Zn alloys were produced by equal channel angular extrusion (ECAE) with 120° die and 16 extrusion passes. The influence of extrusion temperature and deformation route on the microstructure and mechanical properties of these Al-Zn alloys were investigated.
As the extrusion temperature increases, the average grain size of the Al-15wt%Zn increases, and the dislocation density within the grains decreases. As the extrusion temperature increase from 100 °C to 200 °C, the fraction of high angle grain boundary (HAGB) reduces from 67% to 26%, and the hardness decreases from 74.8 Hv to 49 Hv, which could be attributed to an increased recovery rate with increasing extrusion temperature.
Comparing the microstructures resulted from route Bc and route C, it is noted that route Bc produces higher proportion of equiaxed grains, and route C results in more elongated grains. In terms of the efficiency of generating HAGB, route Bc produces higher proportion of HAGBs, which are uniformly distributed, while route C produces less HAGBs, which are mainly distributed in direction parallel to the extrusion direction.
As the extrusion temperature increases, the tensile strength of Al-15wt%Zn decreases due to increasing grain size, but a substantial increase in ductility is realized, which might be due to an increased proportion of HAGBs. Different extrusion route causes little difference in the strength of the Al-Zn alloy, but it affects the tensile elongation.

論文審定書 i
致謝 ii
摘要 iii
Abstract iv
目錄 v
表目錄 viii
圖目錄 viii
第一章 前言 1
第二章 文獻回顧 2
2-1 大量塑性變形與晶粒細化 2
2-2 等徑轉角擠型 3
2-3 影響ECAE製程之參數 4
2-3-1 擠製模角影響 4
2-3-2 擠製路徑影響 5
2-3-3 擠製溫度影響 6
2-3-4 擠製道次影響 8
2-3-5 合金效應 9
2-4 超細晶金屬的晶界形成與特性 10
2-5 超細晶金屬之機械性質 12
2-5-1 超細晶金屬之拉伸變形行為 12
2-5-2 超細晶金屬的強度 13
2-5-3 超細晶金屬的延展性 13
2-6 Al-Zn合金 14
2-6-1 Al-Zn合金簡介 14
2-6-2 超細晶Al-Zn合金近期研究結果 15
第三章 研究目的 18
第四章 實驗方法 19
4-1 實驗材料 19
4-2 均質化處理 19
4-3 等徑轉角擠型(ECAE) 19
4-4 微硬度測試 20
4-5 X光繞射分析 20
4-6 微結構分析 21
4-7 電子背向散射繞射(EBSD)分析 22
4-8 拉伸測試(tensile test) 22
第五章 實驗結果 24
5-1 擠製溫度對ECAE擠製後影響 24
5-1-1 微硬度變化 24
5-1-2 固溶量 24
5-1-3 微結構觀察 25
5-2 擠製路徑對ECAE擠製後影響 26
5-2-1 微硬度變化 26
5-2-2 微結構觀察 26
5-3 拉伸性質 28
5-3-1 擠製溫度對拉伸性質的影響 28
5-3-2 擠製路徑對拉伸性質的影響 29
第六章 討論 30
6-1 添加Zn對Al-Zn合金經ECAE擠製後變形組織的影響 30
6-2 擠製溫度對ECAE擠製後微結構演化的影響 31
6-3 擠製路徑對ECAE擠製後微結構演化的影響 32
6-4 機械性質 33
6-4-1 擠製溫度對ECAE擠製後機械性質的影響 33
6-4-2 擠製路徑對ECAE擠製後機械性質的影響 34
第七章 結論 36
參考文獻 37

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