本實驗選用AA7075-T6鋁合金，藉由摩擦攪拌製程所產生的巨量塑性變形以達到細化微結構的效果，以及產生的高摩擦熱致使基材中的析出物回溶至基材中。以製備具有固溶之極細晶析出硬化型鋁合金，並透過人工時效，達到析出硬化的效果。經摩擦攪拌製程後，鋁晶粒由原材的200 μm細化至1~5 μm。實驗結果中發現，在高冷卻速率的條件下，基材有較高的固溶度，經人工時效後，降伏強度與抗拉強度為534±4 MPa、629±3 MPa，延展性為19±1 %。摩擦攪拌製程在冷卻的過程中所發生的再析出現象，此現象受到製程參數中的走速及冷卻氛圍影響甚為顯著，而轉速及道次的影響次之。

In this study, friction stir processing was used to fabricate the ultrafine grained microstructure from AA7075-T6 plate, and then, the artificial aging was applied to improve the mechanical properties. In the observations, the grain size is refined to micron sized. the degree of re-solution is proportional to the cooling rate, which was significant influenced by traverse speed and cooling surrounding. The result also indicates the re-precipitate phenomena is controlled by the cooling rate. In high cooling rate case, the degree of re-solution is large, after the artificial aging, yield strength and ultimate tensile strength are 534±4 MPa and 629±3 MPa, elongation is 19±1 %.

論文審定書 i
摘要 ii
Abstract iii
目錄 iv
表目錄 vii
圖目錄 viii

第一章 前言 1
1.1 背景說明 1
1.2 研究目的 2
第二章 文獻回顧 3
2.1 熱處理型鋁合金 3
2.2 極細晶鋁合金研究 5
2.3 摩擦攪拌製程 8
2.3.1 摩擦攪拌製程 8
2.3.2 微觀結構特徵 10
2.3.3 製程參數 12
2.3.4 冷卻氛圍 13
第三章 實驗方法 15
3.1 實驗材料 15
3.2 摩擦攪拌製程 15
3.3 人工時效處理 16
3.4 微結構分析 16
3.4.1 X光繞射分析 16
3.4.2 掃描式電子顯微鏡 16
3.4.3 穿透式電子顯微鏡 17
3.4.4 背向散射電子繞射分析 17
3.5 機械性質 18
3.6 試片代號 19
第四章 實驗結果 20
4.1 微結構分析 20
4.1.1 工具頭尺寸 20
4.1.2 道次 20
4.1.3 轉速 21
4.1.4 走速 21
4.1.5 微結構觀察 22
4.2 機械性質 23
4.2.1 道次 23
4.2.2 轉速 25
4.2.3 走速 27
4.3 冷卻氛圍 29
第五章 討論 31
5.1 摩擦攪拌熱輸入量影響對再析出現象之影響 31
5.2 析出行為 32
5.3 強化機構 33
第六章 結論 36
第七章 參考文獻 37
表次 40
圖次 47

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