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系統識別號 U0026-2406202013504300
論文名稱(中文) 應變速率及電流密度在鋁合金(7075-T6)高速撞擊特性與微觀組織之效應分析
論文名稱(英文) Effects of current density and strain rate on the dynamic impact response and microstructural evolution of 7075-T6 aluminum alloy
校院名稱 成功大學
系所名稱(中) 機械工程學系
系所名稱(英) Department of Mechanical Engineering
學年度 108
學期 2
出版年 109
研究生(中文) 陳彤
研究生(英文) Tong Chen
學號 N16074962
學位類別 碩士
語文別 中文
論文頁數 91頁
口試委員 指導教授-李偉賢
口試委員-王俊志
口試委員-黃永茂
中文關鍵字 霍普金森試驗機  電流輔助成形  電塑效應  鋁合金7075-T6  高應變速率  差排 
英文關鍵字 7075-T6 aluminum alloy  Hopkinson pressure bar  strain rate  current  dislocation density 
學科別分類
中文摘要 本實驗透過霍普金森高速撞擊試驗機結合電流輔助成形裝置(EAM),來分析鋁合金7075-T6在高應變速率下對於有無通電之塑性變形行為的改變以及微觀結構的探討。分別於實驗條件在不同應變速率(2200s-1、2800s-1、3000s-1)及有無通電電流(0A、5.05A)下進行本實驗,以利深入的探討在塑性變形行為的巨觀機械性質和維氏硬度的分析,以及透過掃描式電子顯微鏡(SEM)和穿透式電子顯微鏡(TEM)來進行微觀結構分析,以釐清應變速率以及電塑效應在微觀結構的改變是如何影響巨觀之機械性質。
透過實驗之分析,可以從應力-應變曲線觀察到在所有實驗條件下皆有應變速率強化之效應,且塑性變形行為後期熱軟化效應皆大於應變硬化效應,而在達到應變速率為3000s-1時,電塑效應才有顯著的影響;在應變速率敏感性係數以及熱活化體積分析下,應變速率2200s-1到2800s-1區間電塑效應皆不明顯,而在應變速率到達2800s-1到3000s-1的區間時,電塑效應的影響十分明顯。在硬度的測試下,所有實驗條件皆比未撞擊之母材硬度值來得高,而未通電的硬度值也皆比通電下的硬度值來的高,但在應變速率為2800s-1到3000s-1的區間時,其通電下的硬度值逐漸下降,因此在應變速率超過2800s-1是一個轉折點,在此應變速率之後之成形性上升。
透過掃描式電子顯微鏡(SEM)觀察應變速率3000s-1且未通電之破斷面,可以發現在此實驗條件下之塑性變形中為延性破壞;在穿透式電子顯微鏡下(TEM)觀察到差排密度在應變速率為3000s-1時,通電下的密度小於未通電,符合應力-應變曲線之結果。
英文摘要 This study investigates the deformation behavior and dislocation substructure of 7075-T6 aluminum alloy under different strain rate and electric current by using split–Hopkinson pressure bar equipped with the electrically-assisted manufacturing system at strain rates ranging from 2200s-1 to 3000s-1and at constant current of 0A and 5.05A, respectively. The effects of strain rate and electric current on the mechanical properties and dislocations substructure were evaluated, and the relationships between mechanical properties and dislocations substructure were also discussed.
The experimental results show that the strain rate and current play a key role on the mechanical response. For a given strain rate, the flow stress increases with increasing current, except for the specimen deformed at strain rate of 3000s-1. Under a constant current, the increase of the flow stress with strain rate was observed. An obvious variation of the strain rate sensitivity and thermal activation volume with strain rate and current was also found。The Vickers hardness measurement show that the micro-hardness was affected strongly by the strain rate and current.
SEM observation results show that the fracture of the specimens occurs only for the specimen deformed at 3000s-1 and 0A and was dominated by a ductile mode. Moreover, the TEM observations results show that for a given current, the dislocation density increases with increasing strain rate. Under the constant strain rate, the dislocation density increases with increasing current for the specimen deformed at 2200s-1, but decreases with increasing current at 3000s-1. The relationship between work-hardening stress and square root of the dislocation density can be described by the Bailey-Hirsch equation.
論文目次 中文摘要 I
ABSTRACT III
致謝 XI
總目錄 XII
表目錄 XV
圖目錄 XVI
符號說明 XIX
第一章 緒論 1
第二章 理論探討與文獻回顧 4
2-1 鋁合金簡介 4
2-1-1 鋁與鋁合金 4
2-1-2 鋁合金分類與熱處理製程 5
2-1-3 鋁合金7075-T6介紹與應用 8
2-2 電流輔助成形(Electrically-Assisted Manufacturing) 9
2-2-1 電流輔助成形簡介 9
2-2-2 焦耳熱效應 10
2-3 塑性變形機械測試類別 11
2-3-1 靜態或極低之應變速率(〖10〗^(-8)<ε ̇<〖10〗^(-5) s^(-1)) 12
2-3-2 低速之應變速率(〖10〗^(-5)<ε ̇<〖10〗^0 s^(-1)) 12
2-3-3 中速之應變速率(〖10〗^0<ε ̇<〖10〗^2 s^(-1)) 12
2-3-4 高速之應變速率(〖10〗^2<ε ̇<〖10〗^4 s^(-1)) 12
2-3-5 極高速之應變速率(〖10〗^4<ε ̇<〖10〗^7 s^(-1)) 12
2-4 一維波傳理論 13
2-5 霍普金森高速撞擊試驗機之原理 15
2-6 材料塑性變形機制 18
2-6-1 恆溫機制 19
2-6-2 熱活化機制 19
2-6-3 差排黏滯機制 20
2-7 電塑效應對於差排之影響 21
第三章 實驗方法及步驟 35
3-1 實驗流程 35
3-2 實驗儀器與設備 35
3-2-1 霍普金森撞擊試驗機 35
3-2-2 電流輔助成型裝置 37
3-2-3 慢速切割機 37
3-2-4 研磨拋光機 38
3-2-5 震動拋光機 38
3-2-6 維氏硬度機(Vickers hardness test) 38
3-2-7 高階三束型聚焦離子束顯微鏡 39
3-2-8 掃描式電子顯微鏡(SEM) 39
3-2-9 穿透式電子顯微鏡(TEM) 39
3-3 實驗步驟 40
3-3-1 實驗試件製備 40
3-3-2 動態衝擊試驗 40
3-3-3 硬度測試試片製備 41
3-3-4 掃描式電子顯微鏡(SEM)試片製備 41
3-3-5 穿透式電子顯微鏡(TEM)試片製備 42
第四章 實驗結果與討論 45
4-1 應力-應變曲線 45
4-2 應力、應變與應變速率之關係 46
4-3 應變速率敏感性係數 47
4-4 熱活化體積 48
4-5 維氏硬度觀察 49
4-6 掃描式電子顯微鏡(SEM)斷面觀察 50
4-7 穿透式電子顯微鏡(TEM)結構觀察 51
第五章 結論 80
參考文獻 83
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