本研究選用AZ31鎂合金軋延板材，以等徑轉角擠製(Equal Channel Angular Extrusion, ECAE)，採用通道交角Φ為90°及120°，外側弧角Ψ皆為0°的模具，在擠製溫度為115℃至225℃之間，應變率在0.068 /s至1.218 /s之間，分別以路徑A、Bc、C擠製不同道次。
研究結果顯示，AZ31經ECAE後的晶粒細化機制為動態再結晶，與傳統ECAE鋁、銅合金不同，而且經ECAE後的晶粒尺寸，由擠製溫度和擠製應變率來決定，當擠製溫度下降或擠製應變率增快時，可得到較小的晶粒，而擠製道次只影響動態再結晶的比例，不會改變最終的晶粒尺寸。但是在擠製過程中，若擠製溫度過低，或擠製應變率過快，皆會使試棒產生裂縫，此外，起始晶粒尺寸與起始texture也是影響試棒能成功擠製的關鍵因素。本研究發展出多重降溫擠製程序，即先在較高擠製溫度、以較快的擠製應變率進行ECAE，先將鎂合金晶粒初步均勻細化，以便能在較低擠製溫度、以較慢的擠製應變率成功擠製ECAE，繼續細化晶粒，如此擠製出極細晶的鎂合金。
(1) 研究中也發現，無論初始texture為何，以路徑A進行擠製，鎂合金之basal plane隨擠製道次增加，而逐漸旋轉至與Z面平行。ECAE鎂合金的機械性質則是受晶粒尺寸與texture的影響，晶粒尺寸愈小或是basal plane愈平行拉力軸方向，降伏強度愈高。在相同晶粒尺寸條件下，以不同路徑擠製，因為texture的影響，使得路徑A的降伏強度高於路徑Bc、路徑C。利用多重擠製程序可使晶粒細化至 0.37μm，其強度高達372MPa。

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目錄 頁次
表目錄………………………………………………………………….Ⅳ
圖目錄………………………………………………………………….Ⅵ
壹 前言…………………………………………………………………1
貳 文獻回顧……………………………………………………………2
2-1 等徑轉角擠型 (ECAE)…………………………...…………..2
2-1-1 ECAE之原理………………...…………….…………...2
2-2 影響ECAE變形之參數………………………...……...……..2
2-2-1 模角效應…………………………..……….….…...…..2
2-2-2 擠製道次的影響…………………..……….….……..5
2-2-3 擠製路徑的影響……………………………………..8
2-2-4 擠製應變率的影響…………………….……………..11
2-2-5 擠製溫度的影響……………...………….……...…...12
2-3 ECAE變形後的機械性質………………………...…..…….14
2-3-1 晶粒細化對機械性質的影響……………...….…….14
2-3-2 Texture對機械性質的影響……………...………….15
2-4 鎂合金的變形機制與微觀組織…………….………...……...17
2-4-1 低溫下的變形機制………………………..….……..17
2-4-1-1 變形雙晶的機制……………………..…....17
2-4-2 高溫下的變形機制………………………..……...….19
2-4-2-1 動態再結晶的機制………………………...19
2-4-3 低溫下的微觀組織………………………..…..….….20
2-4-4 高溫下的微觀組織………………………..……...….22
2-5 ECAE對鎂合金微觀組織的影響………...………….….……25
2-5-1 ECAE的成功條件……………..…..………….…….26
2-5-2 ECAE的晶粒細化條件……...….………...………...27
2-5-2-1 擠製道次的影響…………………………...27
2-5-2-2 擠製溫度的影響…………………...……...28
2-5-3 ECAE的晶粒細化機制……...….…………..………...29
2-5-4 ECAE擠製後的texture變化..………………………32
2-5-4-1 Basal plane平行剪平面?………….……...32
2-5-4-2 擠製溫度的影響…………………………...34
2-5-4-3 擠製路徑的影響………………….…..…...34
參 研究目的………………………………………………….………37
肆 實驗方法………………………………………………….………38
4-1 材料及ECAE設備…………………….…………….………38
4-2 ECAE試棒製作………….………….……….….…..……38
4-3 OM與SEM的試片製備…………………….……..……39
4-4 TEM的試片製備...…………………………….…….……40
4-5 SEM與TEM的晶粒尺寸量測……….…….…….……40
4-6 Texture的試片製備….……….…..………….………..….41
4-7 EBSD的試片製備….……….……………….…………….41
4-8 拉伸試片的試片製備….………….………….……………42
伍 實驗結果……………………………………………………….…43
5-1 擠製道次的影響…….…………………………….……….43
5-2 擠製路徑的影響…….…….….…………………………...….44
5-3 擠製應變率的影響….……………………….…………….45
5-4 擠製溫度的影響………………………...……………………45
5-5 模角效應的影響…………...…….……..………………….…46
5-6 起始晶粒大小的影響………….……………………………47
5-7 起始texture的影響…………………………………….……48
陸 討論…………………………………………………………….…50
6-1 ECAE的晶粒細化機制….…….……..…………………….50
6-2 ECAE擠製參數對晶粒細化的影響…….………….…...…51
6-2-1 擠製道次的影響……………..…..………….....…….51
6-2-2 擠製路徑的影響……………..…..…………….…….52
6-2-3 擠製應變率的影響…………..…..………………….53
6-2-4 擠製溫度的影響……………..…..…………....…….53
6-2-5 模角效應的影響……………..…..…………..…….54
6-3 ECAE的晶粒細化條件….…………….………………...…54
6-4 ECAE的成功條件……...………………………….…………55
6-5 ECAE後的texture變化..………………………….…………57
6-6 ECAE後的機械性質……….…………………………………61
柒 結論………………………………………………………….……65
捌 參考文獻………………………………………………………….67

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