本研究主要目的為探討熱處理對極細晶(ultrafine grain, UFG)Al-15Zn合金機械性質之影響。極細晶Al-15Zn合金是透過等徑轉角擠型(ECAE)以路徑Bc進行擠製。為了在室溫擠製，在均質化結束後，先利用前熱處理來調整Al-15wt%Zn的強度，ECAE擠製12道次後的Al-15Zn在150 ⁰C~250 ⁰C進行後熱處理。接著透過穿透式電子顯微鏡及電子背向散射繞射分析來觀察極細晶Al-15Zn合金在不同處理條件下的微結構，然後利用微硬度測試及拉伸測試來分析機械性質。
隨著擠製道次增加晶粒尺寸縮小，Zn析出物粗化，同時也會有小的Zn析出物析出。擠製道次對極細晶Al-15Zn合金的影響是，前2道次硬度上升，後續的道次硬度下降。
針對後熱處理的影響可以歸納為以下幾點：
(1)在小於完全固溶溫度(200 ⁰C以下)進行後熱處理時，Al晶粒成長、Zn析出物粗化。與ECAE後相比，降伏強度與最大抗拉強度下降，而均勻伸長率及總伸長率則只有些微變化。
(2)在接近完全固溶溫度(約200 ⁰C~225 ⁰C)進行後熱處理時，Al晶粒成長，同時伴隨著相當多的低角度晶界出現。與ECAE後相比，此合金具有較低的降伏強度，加工硬化率提高，伸長率大幅增加。
(3)在大於完全固溶溫度(225 ⁰C以上)進行後熱處理時，Al晶粒尺寸明顯成長。與225 ⁰C後熱處理相比，此合金最大抗拉強度和伸長率較低。

In this work, the effect of heat treatment on mechanical properties of ultrafine grained (UFG) Al-15Zn alloy is studied. The UFG Al-15Zn alloy was processed by equal channel angular extrusion (ECAE) with route Bc. A pre-heat treatment after homogenization was applied to adjust the hardness of the Al-15Zn alloy so that it could be extruded at room temperature. The Al-15Zn alloy processed by 12 ECAE passes was subjected to post-heat treatment at 150-250 ⁰C. The microstructure of the UFG Al-15Zn alloy after various processing conditions was revealed by using transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD), and mechanical properties were studied by using microhardness test and tensile test.
Increasing ECAE passes, the aluminum grain size was reduced, and there were coarsening of large Zn particles and precipitation of fine Zn particles at the same time. The effect of increasing ECAE passes on the hardness of the UFG Al-15Zn alloy is hardening in the first two passes and softening in the following passes.
The effect of post-ECAE heat treatment can be summarized as follows:
(1) After post-heat treatment at temperatures below 200⁰C, the fully solution temperature for Al-15Zn, the size of Zn particles and the aluminum grain size increased. As compared with the as-ECAE condition, both yield stress and tensile strength decreased with little change in elongation.
(2) After post-heat treatment at temperatures near the fully solution temperature (200-225 ⁰C), the aluminum grain size increased and considerable amount of low angle boundary (LAB) appeared. The alloy exhibited lower yield stress, enhanced work-hardening rate and superior elongation comparing with the as-ECAE condition.
(3) After post-heat treatment at 250 ⁰C, above the fully solution temperature, the aluminum grain size increased considerably. The alloy exhibited lower ultimate tensile strength and elongation as compared with that being heat treated at 225 ⁰C.

致謝 i
摘要 ii
Abstract iii
目錄 iv
表目錄 vii
圖目錄 ix
第一章 前言 1
第二章 文獻回顧 3
2-1 等徑轉角擠型 3
2-1-1 ECAE的發展與原理 3
2-1-2 其他ECAE技術 3
2-2 影響ECAE之製程參數 4
2-2-1 模角的影響 4
2-2-2 路徑的影響 5
2-2-3 擠製道次的影響 6
2-2-4 擠製溫度的影響 6
2-3 超細晶金屬之機械性質 7
2-3-1 超細晶金屬之拉伸變形行為 7
2-3-2 超細晶金屬的強度 8
2-3-3 超細晶金屬的延展性 8
2-3-4 超細晶金屬的應變速率敏感值 11
2-3-5 超細晶金屬的晶界形成與特性 12
2-4 Al-Zn合金 14
2-4-1 Al-Zn合金之介紹[1] 14
2-4-2 Al-Zn 合金經摩擦攪拌製程之機械性質 14
2-4-3 Al-Zn合金經大量塑性變形後之軟化現象 15
2-4-4 Al-15wt%Zn合金經ECAE製程之特性 17
2-5 Al合金經熱處理與大量塑性變形後的性質 18
2-5-1 熱處理簡介 18
2-5-2 Al合金經熱處理後的晶粒成長 18
2-5-3 Al合金經熱處理與大量塑性變形後的機械性質 19
第三章 研究目的 20
第四章 實驗方法 22
4-1 實驗材料 22
4-2 均質化處理 22
4-3 前熱處理 22
4-4 X光繞射分析 23
4-5 等徑轉角擠型 23
4-6 後熱處理 24
4-7 微硬度測試 24
4-8 穿透式電子顯微鏡分析 25
4-9 電子背向散射繞射分析 25
4-10 拉伸測試 26
第五章 實驗結果 28
5-1 前熱處理之影響 28
5-1-1 前熱處理後的微硬度測試 28
5-1-2 前熱處理對Zn固溶量的影響 29
5-1-3 前熱處理對晶粒尺寸的影響 29
5-2 ECAE的影響 29
5-2-1 ECAE後的微硬度測試 30
5-2-2 ECAE對晶粒尺寸與晶界差角分布的影響 30
5-2-3 ECAE後的TEM微結構觀察 31
5-2-4 ECAE後的拉伸測試 32
5-3 後熱處理的影響 32
5-3-1後熱處理完的微硬度測試 32
5-3-2後熱處理對晶粒尺寸與晶界差角分布的影響 33
5-3-3後熱處理完之TEM微結構觀察 34
5-3-4 後熱處理完的拉伸測試 34
5-3-5 後熱處理對Zn固溶量的影響 35
第六章 結果討論 36
6-1 均質化處理及前熱處理的影響 36
6-2 ECAE擠製的影響 37
6-2-1 ECAE擠製對晶粒形貌之影響 37
6-2-2 ECAE擠製對析出物的影響 39
6-2-3 ECAE擠製對機械性質的影響 40
6-3 後熱處理之影響 41
6-3-1 後熱處理對晶粒形貌的影響 41
6-3-2 後熱處理對析出物的影響 43
6-3-3 後熱處理對機械性質的影響 43
第七章 結論 46
參考文獻 47

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