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研究生:左啟和
研究生(外文):Chi-Ho Tso
論文名稱:鋁鎂合金5052塑性變形不穩定性之研究
論文名稱(外文):Plastic Instabilities of Al-Mg 5052 Alloy
指導教授:鄭憲清郭振明
指導教授(外文):Shian-Ching JangChen-Ming Kuo
學位類別:碩士
校院名稱:義守大學
系所名稱:材料科學與工程學系
學門:工程學門
學類:材料工程學類
論文種類:學術論文
論文出版年:2002
畢業學年度:90
語文別:中文
論文頁數:88
中文關鍵詞:鋁鎂合金5052動態應變時效塑性不穩定
外文關鍵詞:Al-Mg 5052 Alloydynamic strain ageingplastic instability
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本研究是於室溫下對鋁鎂合金5052O在應力率改變試驗中的塑性不穩定性加以探討,並以TEM觀察在不同停滯時間及不同最終應力下受力試驗片的顯微結構及變化。
在應力率改變的實驗中,可以明顯發現到應變延遲及塑性不穩定現象。實驗過程中,在塑性不穩定現象發生之前,試驗片應變的變化非常小,一直到塑性不穩定發生之後,試驗片才有顯著的大形變﹔如果試驗片沒有不穩定現象,則其應變幾乎沒有變化。塑性變形不穩定性現象的發生與應力率及停滯時間有關,藉由實驗結果討論分析,塑性變形不穩定性的現象是由動態應變時效所影響,也就是試驗片本身的固溶強化溶質鎂原子與差排氛圍交互作用的結果。
另本研究運用數值分析方法模擬應力率改變實驗,以運動變形原理及結構進化公式所組成的熱活化塑性變形理論來模擬金屬塑性變形機構。經由適當的參數值改變,所得到的理論值與實驗數據非常吻合,說明了以熱活化變形為基礎的金屬塑性變形理論,經由適當的參數值改變,可來描述在室溫下應力率改變實驗中各種的變形現象。
Plastic instability is observed during stress rate change test of aluminum-magnesium alloy 5052 at room temperature. TEM observations reveal the microstructure and dislocation morphology of specimens at different final stress level and retention time.
In the stress rate change tests, strain retardation and plastic deformation instability are observed. During the stress rate change test, plastic strain is insignificant until the plastic instability occurs. If there is no unstable phenomena, the plastic strain rate would practically have no changes from beginning to end. The occurrence of plastic instability is related to the applied stress rate and retention time. By the argument of dynamic strain ageing effect, the plastic instability could be justified as the interaction between solid solution element, magnesium, and dislocations.
In order to modeling the plastic deformation mechanisms, thermally activated kinetic flow theory coupled with structural evolution law has been employed. Numerical methods of these coupled nonlinear equations are utilized. By changing the values of suitable parameters to simulate the microstructure change of instability, plastic instability could be modeled. Excellent agreement between numerical simulations and experimental data is observed.
中文摘要 Ⅰ
英文摘要 Ⅱ
誌謝 Ⅲ
總目錄 Ⅳ
圖目錄 Ⅶ
表目錄 ⅩⅣ
符號 ⅩⅤ
第一章 緒論 01
第二章 實驗分法與步驟 04
2.1應力率改變實驗 04
2.1.1 實驗設備 04
2.1.2 試驗片 04
2.1.2.1 試驗片母材之金相組織觀察 05
2.1.2.2 試驗片退火前之金相組織 05
2.1.2.3 試驗片退火後之金相組織 06
2.1.3 實驗設計 07
2.1.4 MTS PID 微調 07
2.2 TEM顯微結構觀察 08
2.2.1 TEM試片製作 09
2.2.2 微硬度試驗 11
第三章 實驗結果 19
3.1 應力率改變實驗結果 19
3.1.1 實驗數據資料轉換 19
3.1.2 應力率改變實驗結果 20
3.1.3 固定應力率拉伸實驗結果 21
3.2 TEM顯微組織觀察結果 22
第四章 分析與討論 40
4.1 應力率改變實驗與固定應力率拉伸實驗結果討論 40
4.1.1 5052鋁合金的強化機構 40
4.1.2 氛圍的產生 41
4.1.3 氛圍對移動中差排的牽制 43
4.1.4 動態應變時效 45
4.1.5 與5005鋁鎂合金應力率改變實驗比較分析 46
4.1.6 提要 47
4.2 TEM顯微組織分析討論 47
4.2.1 由最終應力比較分析 48
4.2.2 由停滯時間比較分析 48
4.2.3 與微硬度實驗結果比較分析 48
4.2.4 討論 49
第五章 塑性變形理論模式及數值分析 55
5.1 變形理論 55
5.1.1 運動變形理論 55
5.1.2結構進化公式 57
5.2 數值分析方法 59
5.2.1 演算方式 60
5.2.2計算機程式 62
5.3 實驗數據與數值運算結果比較 62
5.3.1 利用固定應力率拉伸實驗結果求得 與 值 62
5.3.2 未發生不穩定現象的應力率改變實驗數值分析結果 63
5.3.3 發生不穩定現象的應力率改變實驗數值分析結果 63
5.3.4 不穩定性臨界點實驗及其數值分析結果 64
5.3.5 與 敏感度分析 65
5.3.6 討論 66
第六章 結論 78
參考文獻 80
附錄A 材質證明 84
附錄B 計算機程式 85
圖目錄
Figure 1:MTS servohydraulic material test system. 12
Figure 2:TestStar II close loop control block diagram. 12
Figure 3:Specimen dimensions according to ASTM E 8M — 94a standard sheet-types specimen. 14
Figure 4:Tensile stress-strain curve of 5052O Al-Mg alloy. 15
Figure 5:Polarized microscopic pictures of 5052F Al-Mg alloy; (a) normal direction, (b) longitudinal direction, (c) transverse direction, in respect of rolling surface. 16
Figure 6:Polarized microscopic pictures of 5052O Al-Mg alloy; (a) normal direction, (b) longitudinal direction, (c) transverse direction, in respect of rolling surface. 17
Figure 7:Input command for MTS controller. 18
Figure 8:PID tuning controls. 18
Figure 9:Time history plots of true stress and inelastic true strain at = 5 MPa/s, = 85 MPa, retention time T = 4s; no plastic instability occurs. 23
Figure 10:Time history plots of true stress and inelastic true strain at = 10 MPa/s, = 85 MPa, retention time T = 4s; plastic instability occurs. 23
Figure 11:Time history plots of true stress and inelastic true strain at = 10 MPa/s, = 85 MPa, retention time T = 4s; no plastic instability occurs. 24
Figure 12:Time history plots of true stress and inelastic true strain at = 10 MPa/s, = 85 MPa, retention time T = 40s; no plastic instability occurs. 24
Figure 13:Time history plots of true stress and inelastic true strain at = 20 MPa/s, = 85 MPa, retention time T = 1s; plastic instability occurs. 25
Figure 14:Time history plots of true stress and inelastic true strain at = 20 MPa/s, = 85 MPa, retention time T = 2s; plastic instability occurs. 25
Figure 15:Time history plots of true stress and inelastic true strain at = 20 MPa/s, = 85 MPa, retention time T = 3s; plastic instability occurs. 26
Figure 16:Time history plots of true stress and inelastic true strain at = 20 MPa/s, = 85 MPa, retention time T = 4s; plastic instability occurs. 26
Figure 17:Time history plots of true stress and inelastic true strain at = 20 MPa/s, = 85 MPa, retention time T = 10s; plastic instability occurs. 27
Figure 18:Time history plots of true stress and inelastic true strain at = 20 MPa/s, = 85 MPa, retention time T = 40s; plastic instability occurs. 27
Figure 19:Time history plots of true stress and inelastic true strain at = 5 MPa/s, = 120 MPa, retention time T = 4s; no plastic instability occurs. 28
Figure 20:Time history plots of true stress and inelastic true strain at = 10 MPa/s, = 120 MPa, retention time T = 4s; plastic instability occurs. 28
Figure 21:Time history plots of true stress and inelastic true strain at = 10 MPa/s, = 120 MPa, retention time T = 4s; no plastic instability occurs. 29
Figure 22:Time history plots of true stress and inelastic true strain at = 10 MPa/s, = 120 MPa, retention time T = 40s; no plastic instability occurs. 29
Figure 23:Time history plots of true stress and inelastic true strain at = 20 MPa/s, = 120 MPa, retention time T = 1s; plastic instability occurs. 30
Figure 24:Time history plots of true stress and inelastic true strain at = 20 MPa/s, = 120 MPa, retention time T = 2s; plastic instability occurs. 30
Figure 25:Time history plots of true stress and inelastic true strain at = 20 MPa/s, = 120 MPa, retention time T = 3s; plastic instability occurs. 31
Figure 26:Time history plots of true stress and inelastic true strain at = 20 MPa/s, = 120 MPa, retention time T = 4s; plastic instability occurs. 31
Figure 27:Time history plots of true stress and inelastic true strain at = 20 MPa/s, = 120 MPa, retention time T = 10s; plastic instability occurs. 32
Figure 28:Time history plots of true stress and inelastic true strain at = 20 MPa/s, = 120 MPa, retention time T = 40s; plastic instability occurs. 32
Figure 29:True stress vs. inelastic true strain at constant engineering stress rate 5MPa/s. 33
Figure 30:True stress vs. inelastic true strain at constant engineering stress rate 10MPa/s. 33
Figure 31:True stress vs. inelastic true strain at constant engineering stress rate 20MPa/s. 34
Figure 32:Time history plots of true stress and inelastic true strain at constant stress rate 5 MPa/s. 34
Figure 33:Time history plots of true stress and inelastic true strain at constant stress rate 10 MPa/s. 35
Figure 34:Time history plots of true stress and inelastic true strain at constant stress rate 20 MPa/s. 35
Figure 35:Dislocation morphology of {110} zone at undeformed condition, at (a) 20,000X, (b) 40,000X. 36
Figure 36:Dislocation morphology of {110} zone at different input command, at 40,000X . 37
Figure 37:Dislocation morphology of {110} zone at different input command, at 20,000X. 38
Figure 38:Dislocation morphology of {110} zone, at (a) 60,000X, (b) 40,000X. 39
Figure 39:Relative Stress at initial instability versus Retention Time diagram, at = 20 MPa/s, = 85 MPa and 120 MPa. 51
Figure 40:Thermally activated motion of dislocations past point obstacles. 68
Figure 41:Obstacle thermodynamics ( rectangular obstacles ). 68
Figure 42:Mechanism of strain hardening. 69
Figure 43:Mechanism of dynamic recovery. 69
Figure 44:Comparisons between experimental data and numerical simulations of inelastic true strain-time plot for constant stress rates at 5 , 10 and 20 MPa/s. 70
Figure 45:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations for stress rate change test at = 10 MPa/s, = 85 MPa, no plastic instability occurs. 70
Figure 46:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations for stress rate change test at = 10 MPa/s, = 120 MPa, no plastic instability occurs. 71
Figure 47:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations for stress rate change test at = 10 MPa/s, = 85 MPa, plastic instability occurs. 71
Figure 48:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations for stress rate change test at = 20 MPa/s, = 85 MPa, plastic instability occurs. 72
Figure 49:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations for stress rate change test at = 10 MPa/s, = 120 MPa, plastic instability occurs. 72
Figure 50:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations for stress rate change test at = 20 MPa/s, = 120 MPa, plastic instability occurs. 73
Figure 51:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations for stress rate change test at = 20 MPa/s, = 76 MPa, no plastic instability occurs. 73
Figure 52:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations for stress rate change test at = 20 MPa/s, = 77 MPa, no plastic instability occurs. 74
Figure 53:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations for stress rate change test at = 20 MPa/s, = 78 MPa, no plastic instability occurs. 74
Figure 54:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations for stress rate change test at = 20 MPa/s, = 79 MPa, plastic instability occurs. 75
Figure 55:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations for stress rate change test at = 20 MPa/s, = 79.5 MPa, plastic instability occurs. 75
Figure 56:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations of different ΔA with same LR for stress rate change test at = 20 MPa/s, = 79 MPa. 76
Figure 57:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations of different LR with same ΔA for stress rate change test at = 20 MPa/s, = 79 MPa. 76
Figure 58:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations of different LR with same ΔA for stress rate change test at = 20 MPa/s, = 79.5 MPa. 77
Figure 59:Comparisons of inelastic true strain-time plot between experimental data and numerical calculations of different LR with same ΔA for stress rate change test at = 20 MPa/s, = 85 MPa. 77
表目錄
Table 1:MTS TestStar II servohydraulic material test system components. 13
Table 2:Relative Stress at initial instability of Al-Mg 5005 and 5052 alloys. 52
Table 3:Width of strip-type cell at different input command. 53
Table 4:Microhardness at different input command. 54
符號
應力率改變實驗控制命令所設定的初始應力率值
應力率改變實驗控制命令所設定的應力率改變值
應力率改變實驗控制命令所設定最後維持的應力值
應力率改變實驗控制命令所設定最初維持的應力值
工程應力
Burgers向量
非彈性工程應變
彈性工程應變
全部的工程應變
Young模數
Boltzmann常數
阻擋差排運動障礙物之間的距離
應變硬化時差排運動的距離
數值分析中所分割的第 個時間
數值分析中所分割的第 個時間
絕對溫度
平均差排移動速率
與晶體結構有關的常數
與晶體結構有關的常數
在第 個時間下剪應變
真實剪應變率
在第 個時間下剪應變
在第 個時間下剪應變率
在第 個時間下剪應變率
Arrhenius關係式的冪指數前項
真實應變
剪力彈性模數
可移動的差排密度
差排密度
真實應力
真實剪應力
障礙物的強度
在第 個時間下剪應力
在第 個時間下剪應力
在第 個時間下障礙物強度
在第 個時間下障礙物強度
原子跳躍頻率
差排振盪頻率
動態回復時兩不同方向差排被消滅的範圍
動態回復時差排被消滅掉所移動的距離
應變硬化時差排密度增加量
動態回復時差排密度減少量
差排脫離障礙物束縛所須的擺動面積
障礙物的自由能
障礙物活化能
數值分析中所分割的時間間隔
外加應力所作的功
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