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姓名 陳學億(Hsueh-I Chen) 查詢紙本館藏 畢業系所 機械工程學系 論文名稱 半固態鎂合金流動行為之研究分析
(The Research of the Flow Behavior of the Semi-Solid State Magnesium Alloy)相關論文 檔案 [Endnote RIS 格式]
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摘要(中) 研究的目的在於探討鎂合金AZ91D在半固態時的流動行為。實驗中，利用可在高溫下量測黏度的同心圓柱黏度計，觀測半固態鎂合金黏漿的視黏度與剪應變和溫度之間的關係。由實驗結果發現，黏漿的視黏度隨著溫度的上升而降低，隨著剪應變率的增加而減少，具有剪變薄流體的特性。並根據本實驗數據，知道數學冪次式中的n值為接近於0.84。鎂合金AZ91D半固態黏漿觸變程度會隨著恆定剪應變率作用時間的增加而變大，但是，剪應力減少比例的曲線會越趨平緩，因為晶粒被球化至一定程度之後，更長的恆定剪應變率作用時間對剪應力將不會有顯著的影響。長時間的攪拌效應會讓視黏度先減少後逐漸增加，由於內部結構從樹枝狀結構破壞成顆粒較小的非樹枝狀結構，晶粒尺寸也會跟著減少，隨著攪拌時間的持續增加，晶粒會因為粗化效應逐漸長大，尺寸也會逐漸增大。不同的固相分率、預先攪拌時間與停留時間對流動性質也會產生影響，當預先攪拌時間固定時，較高固相分率的視黏度會隨著停留時間的增加而增加，這是由於顆粒聚合主導粗化機制並讓包覆液體維持在晶粒裡面；較低固相分率的視黏度會隨著停留時間的增加而減少，因為晶粒內部的包覆液體會藉由奧斯特瓦爾德成長主導的粗化作用被釋放，這將會導致流動性變佳。當固相分率固定時，較短預先攪拌時間的視黏度會隨著停留時間的增加而增加，較長預先攪拌時間的視黏度會隨著停留時間的增加而減少，這都是因為顆粒聚合與奧斯特瓦爾德成長等粗化機制對包覆液體產生不同影響所導致流動性的變化。
摘要(英) In this study, the flow behavior of the semi-solid AZ91D magnesium alloy is investigated by a high-temperature coaxial-cylinder viscometer. The relations between the steady-state apparent viscosity, shear rate and temperature of the magnesium alloy are observed. According to the results, the apparent viscosity decrease as the isothermal temperature and shear rate increase. The semi-solid AZ91D magnesium alloy shows the shear-thinning behavior. Basing on the experimental data, the power-law constant n is around 0.84. As the shearing time of maintained shear rate increase, the thixotropic behavior of magnesium slurry is more obvious. But the curve of reducing ratio is gradual, and the longer shearing time of maintained shear rate would not affect the shear stress. As the stirring time increases, the apparent viscosity initially decreases, and then it follows increasing curve. It is because that the dendritic structure is destroyed into the smaller non-dendritic one. As the stirring time continuously increases, the coarsening effect causes the particle size to increase. The solid fraction, pre-stirring time and resting time have influence on the flow behavior. When the pre-stirring time is fixed, the apparent viscosity increases as the resting time increases at high solid fraction. At the low solid fraction, the apparent viscosity decreases as the resting time increases. When the solid fraction is fixed, the apparent viscosity increases for shorter pre-stirring time as the resting time increases, and the apparent viscosity decreases for longer pre-stirring time as the resting time increases.
關鍵字(中) ★ 鎂合金
★ 半固態
★ 流動行為關鍵字(英) ★ Magnesium Alloy
★ Semi-Solid State
★ Flow Behavior論文目次 目錄
頁碼
中文摘要.........................................................................................................................i
英文摘要........................................................................................................................ii
誌謝...............................................................................................................................iii
符號說明.......................................................................................................................iv
目錄................................................................................................................................v
表目錄.........................................................................................................................viii
圖目錄...........................................................................................................................ix
第一章 緒論..............................................................................................................1
1.1 背景.........................................................................................................................1
1.2 文獻回顧.................................................................................................................2
1.3 研究動機.................................................................................................................3
1.4 研究目的.................................................................................................................4
1.5 研究方法.................................................................................................................5
圖....................................................................................................................................9
第二章 理論基礎...................................................................................................17
2.1 凝固結構...............................................................................................................17
2.2 半固態材料成形之原理.......................................................................................18
2.3 半固態材料之流動特性.......................................................................................20
2.3.1 固相分率對流動的影響................................................................................21
2.3.2 晶粒形狀對流動的影響................................................................................22
2.3.3 包覆液體對流動的影響................................................................................22
2.3.4 攪拌因素對流動的影響................................................................................22
2.3.5 時間因素對流動的影響................................................................................23
2.4 半固態材料的觸變行為.......................................................................................24
2.5 鎂合金AZ91D的流變特性..................................................................................24
圖..................................................................................................................................27
第三章 實驗設備與流程.....................................................................................46
3.1 實驗設備...............................................................................................................46
3.1.1 實驗材料........................................................................................................46
3.1.2 傳動感應系統................................................................................................48
3.1.3 測矩系統........................................................................................................49
3.1.4 恆溫系統........................................................................................................50
3.2 實驗流程...............................................................................................................50
3.2.1 穩態實驗........................................................................................................51
3.2.2 觸變實驗........................................................................................................51
3.2.3 暫態實驗........................................................................................................51
3.2.4 攪拌時間之影響............................................................................................52
3.2.5 固相分率、預先攪拌時間與停留時間之影響............................................52
圖表..............................................................................................................................53
第四章 結果與討論..............................................................................................67
4.1 半固態溫度及剪應變率對鎂合金黏漿穩態流動的影響...................................67
4.1.1 由冪次數學式觀察鎂合金黏漿的穩態流動.................................................68
4.1.2 實驗結果與其他文獻作比較.........................................................................69
4.2 鎂合金AZ91D的觸變行為.................................................................................70
4.2.1 不同剪應變率對鎂合金AZ91D觸變行為的影響.......................................71
4.2.2 剪應變率改變速率對鎂合金AZ91D觸變行為的影響...............................72
4.2.3 不同恆定剪應變率作用時間對鎂合金AZ91D觸變行為的影響...............72
4.2.4 鎂合金AZ91D觸變行為的分析...................................................................73
4.3 鎂合金AZ91D的暫態行為.................................................................................73
4.3.1 剪應變率的瞬間改變對鎂合金AZ91D暫態行為的影響...........................74
4.3.2 鎂合金AZ91D暫態行為的分析...................................................................75
4.4 攪拌時間之效應...................................................................................................75
4.5 鎂合金AZ91D固相分率、預先攪拌時間與停留時間之影響.........................77
4.5.1 固定預先攪拌時間，不同固相分率與停留時間之影響.............................77
4.5.2 固定固相分率，不同預先攪拌時間與停留時間之影響.............................78
圖..................................................................................................................................80
第五章 結論..........................................................................................................109
5.1 穩態流動.............................................................................................................109
5.2 觸變行為.............................................................................................................109
5.3 暫態行為.............................................................................................................110
5.4 攪拌時間之效應.................................................................................................110
5.5 固相分率、預先攪拌時間與停留時間之影響.................................................111
5.6 實驗設備之設計與改良.....................................................................................111
參考文獻.................................................................................................................113
表目錄
頁碼
表3-1 鎂合金AZ91D的化學組成(wt%)..................................................................53
表3-2 鎂合金AZ91D的物理性質............................................................................54
圖目錄
頁碼
圖1-1 三種主要鑄造方法的流程圖............................................................................9
圖1-2 半固態射出成型機之示意圖[6].....................................................................10
圖1-3 半固態黏漿視黏度與模具充填速度關係圖[7].............................................11
圖1-4 鎂鋁合金二元相圖[4].....................................................................................12
圖1-5 毛細管黏度計示意圖[10]...............................................................................13
圖1-6 落球黏度計示意圖[10]...................................................................................14
圖1-7 擠製法黏度計示意圖......................................................................................15
圖1-8 同心圓柱黏度計示意圖..................................................................................16
圖2-1 熔液為正溫度梯度時對固液界面生長的影響[18].......................................27
圖2-2 固液界面的生長(a)平面生長(b)樹枝狀生長[18]..........................................28
圖2-3 熔液為負溫度梯度時對固液界面生長的影響[18].......................................29
圖2-4 二元相圖之偏析效應分析[18].......................................................................30
圖2-5 組成過冷在固液界面凝固處的原由(a)偏析效應造成熔液濃度的不均勻(b)熔液濃度不均勻造成平衡凝固溫度為曲線而與熔液溫度線形成組成過冷[18]...31
圖2-6 不同組成過冷程度對固液界面的影響[18]...................................................32
圖2-7 溫度對合金壓縮變形阻抗的影響..................................................................33
圖2-8 晶粒結構(a)樹枝狀結構(b)球狀結構[2]........................................................34
圖2-9 半固態材料不同固相分率示意圖[2].............................................................35
圖2-10 半固態金屬的流動機制................................................................................36
圖2-11 不同結構的碰撞及結合所產生包覆液體的影響(a)樹枝狀結構(b)球狀[11]...............................................................................................................................37
圖2-12 攪拌對晶粒結構破壞的演化過程[2]...........................................................38
圖2-13 不同固相分率的剪應變率與視黏度關係圖[16].........................................39
圖2-14 Joly等人[14]實驗流程圖...............................................................................40
圖2-15 錫鉛合金黏漿的遲滯現象[14] ....................................................................41
圖2-16 各種觸變性流體的剪應力與剪應變率關係圖(a)假塑性的觸變性流體(b)牛頓性的觸變性流體(c)塑性的觸變性流體(d)黏塑性的觸變性流體[10]..............42
圖2-17 剪應力與剪應變率關係圖[19].....................................................................43
圖2-18 AZ91D的流變鑄造演化過程[17] .................................................................44
圖2-19 Ghosh等人[4]所架構的同心圓柱黏度計.....................................................45
圖3-1 實驗設備示意圖..............................................................................................55
圖3-2 傳動感應系統之內外坩堝尺寸圖..................................................................56
圖3-3 各種材質的坩堝(a)SKD61鋼材(b)石墨材質................................................57
圖3-4 荷重元的樣式與尺寸圖..................................................................................58
圖3-5 訊號放大器的規格與尺寸圖..........................................................................59
圖3-6 滾珠式軸承......................................................................................................60
圖3-7 加熱爐(a)示意圖與(b)實體圖.........................................................................61
圖3-8 穩態實驗流程圖..............................................................................................62
圖3-9 觸變實驗流程圖..............................................................................................63
圖3-10 暫態實驗流程圖............................................................................................64
圖3-11 攪拌時間實驗流程圖....................................................................................65
圖3-12 固相分率、預先攪拌時間與停留時間實驗流程圖....................................66
圖4-1 溫度及剪應變率與鎂合金黏漿視黏度的關係圖..........................................80
圖4-2 在不同剪應變率下，固相分率與視黏度值的關係圖..................................81
圖4-3 在不同固相分率下，剪應變率與視黏度的對數關係圖..............................82
圖4-4 固相分率與冪次式中的n值關係圖..............................................................83
圖4-5 研究結果與文獻的視黏度值比較..................................................................84
圖4-6 實驗過後的內圓錐照片(a)整支(b)前段(c)後段.............................................85
圖4-7 不同剪應變率的觸變行為結果......................................................................86
圖4-8 不同剪應變率改變速率的觸變行為結果......................................................87
圖4-9 不同恆定剪應變率作用時間的觸變行為結果..............................................88
圖4-10 不同恆定剪應變率作用時間的最低剪應力與減少比例............................89
圖4-11 不同剪應變率的暫態行為結果(驟升).........................................................90
圖4-12 不同剪應變率的暫態行為結果(驟降).........................................................91
圖4-13 不同固相分率的暫態行為結果(驟升).........................................................92
圖4-14 不同固相分率的暫態行為結果(驟降).........................................................93
圖4-15 半固態合金剪應變率與剪應力示意圖by H. Peng[34]..............................94
圖4-16 視黏度與攪拌時間關係圖............................................................................95
圖4-17 晶粒結構發展示意圖....................................................................................96
圖4-18 不同攪拌時間的SEM圖(a)10 (b)20 (c)40 (d)90 (e)120(分鐘)...................97
圖4-19 晶粒尺寸與攪拌時間的關係圖....................................................................98
圖4-20 不同固相分率下，視黏度與停留時間關係圖............................................99
圖4-21 晶粒結構發展示意圖..................................................................................100
圖4-22 高固相分率不同停留時間的SEM圖(a)10(b)40(c)90(min)......................101
圖4-23 低固相分率不同停留時間的SEM圖(a)10(b)40(c)90(min)......................102
圖4-24 不同固相分率下，晶粒尺寸與停留時間的關係圖...................................103
圖4-25 不同預先攪拌時間下，視黏度與停留時間關係圖...................................104
圖4-26 晶粒結構發展示意圖..................................................................................105
圖4-27 短預先攪拌時間不同停留時間的SEM圖(a)10(b)40(c)90(min)..............106
圖4-28 長預先攪拌時間不同停留時間的SEM圖(a)10(b)40(c)90(min)..............107
圖4-29 不同預先攪拌時間下，晶粒尺寸與停留時間關係圖...............................108
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指導教授 陳志臣(Jyh-Chen Chen) 審核日期 2009-1-12 推文 plurk
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