本實驗研究鋁鋅合金的機械性質，探討其因不同鋅含量、晶粒尺寸及拉伸速率而展現的機械強度變化趨勢及其塑性變形機制為何。
研究用的實驗樣本以摩擦攪拌製程製作，在適當轉速下，以不同鋅含量的鋁鋅混合粉末為母材，在適當轉速下，共計製作晶粒尺寸為1.5μm、1μm及0.5μm，及鋅含量為2.5wt%、5wt%、7.5wt%、10wt%及15wt% 共15種不同實驗條件的樣本，前述樣本以3種不同拉伸速率(10-3s-1、10-4s-1及10-5s-1)進行拉伸實驗測試，共計得到45組的機械性質實驗數據。
各組數據接著用以製作相對應的工程與真實拉伸應力圖、流動應力-鋅含量圖、Hall-Petch關係圖、m值-鋅含量及m值-晶粒尺寸圖，數據分析後發現在適當實驗條件下，鋁鋅合金可展現固溶軟化效應及反Hall-Petch關係，在超細晶尺度，鋅含量大於11.7wt%的實驗條件下，此兩現象隨拉伸速率下降愈加明顯。
應變速率敏感係數的數據分析結果顯示，當鋁鋅合金展示固溶軟化效應及反Hall-Petch關係的同時，m值有隨鋅含量上升及晶粒尺寸下降而上升的趨勢，此間變化原因可能為鋅元素在晶界處的高擴散係數，其令鋁鋅合金的動態回復效率遠高於他種鋁基合金，隨著鋅含量增高、晶粒尺寸縮小及拉伸速率下降，動態回復效應隨之愈加明顯，使高鋅含量的鋁鋅合金於晶粒尺寸為1μm時，即因晶粒弱化機構而具有反Hall-Petch關係。

In this study, mechanical properties of Al-Zn alloys were conducted, with various parameters including Zn contents, grain size, and tensile strain rate. Experimental samples were all manufactured with friction stir processing method. Samples of Al-Zn alloys with the grain size of 1.5μm, 1μm, or 0.5μm and five Zn concentration were pulled in tension at strain rate of 10-3s-1,10-4s-1 and 10-5s-1 .
The data set were then used to draw engineering and true tensile stress vs. strain curves , flowing stress vs. Zn contents curves, Hall-Petch equation curves, m vs. Zn contents curves and m vs. grain size curves. Quantitative analysis were conducted to discover that solid solute softening and inverse Hall-Petch relation were present in Al-Zn alloys, which were more prominent at slower tensile strain rate when grain size was less than 1μm and the Zn contents was higher than 10wt%.
Quantitative analysis of strain rate sensitivity (m) showed the trends of increasing value of m with higher Zn contents and smaller grain sizes when solid solute softening and inverse Hall-Petch relation were present. The high grain-boundary diffusion coefficient of Zn which accelerates the efficiency of dynamic recovery are considered the main reason. The effect gets more prominent with increasing Zn contents , smaller grain size , and slower tensile strain rate. For Zn concentration higher than 10wt%, dynamic recovery may drive inverse Hall-Petch relation to appear when grain size is about 1μm large.

目錄

論文審定書 i
摘要ii
Abstract. iii
第1章 前言 1
1.1 背景說明 1
1.2 研究動機及目的 3
第2章 文獻回顧 4
2.1 摩擦攪拌製程用於製作超細晶材料 4
2.1.1 摩擦攪拌製程 4
2.1.2 摩擦攪拌製程晶粒尺寸 4
2.2 Al-Zn 合金的基本性質 5
2.2.1 Al-Zn 合金的機械性質 6
2.3 金屬基複合材料的機械性質 6
2.3.1 加工硬化 6
2.3.2 細晶強化 8
2.3.3 Hall-Petch 曲線偏差相關理論 8
2.3.4 應變速率敏感係數 11
2.3.5 動態回復效率之相關理論 14
第3章 實驗方法 16
3.1 實驗材料成分與製備 16
3.1.1 鋁粉與鋅粉 16
3.1.2 實驗塊材製作 16
3.2 摩擦攪拌製程 16
3.2.1 工具頭與夾具 16
3.2.2 摩擦攪拌製成機器簡介 17
3.2.3 摩擦攪拌製程步驟 17
3.3 巨觀結構與微觀組織分析 17
3.3.1 掃描式電子顯微鏡觀察試片的晶粒大小 17
3.3.2 X光繞射分析 17
3.3.3 電子微探儀 (EPMA) 定量分析 18
3.3.4 穿透式電子顯微鏡觀察差排分布情形 18
3.4 機械性質測量 18
3.4.1 拉伸試驗 18
第4章 實驗結果與討論 19
4.1 晶粒大小 19
4.2 X光繞射分析 19
4.3 電子微探儀定量分析結果 20
4.4 拉伸性質量測 20
4.4.1 應力應變曲線 20
4.4.2 鋅原子與拉伸速率的互動對機械性質的影響 21
4.4.3 鋅含量與Hall-Petch relation 關係曲線圖 23
4.4.4 m值變動與拉伸速率及晶粒尺寸關係 24
4.4.5 TEM觀察結果 27
第5章 結論 28
參考文獻 30
表 35
圖 45

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