臺灣博碩士論文加值系統

近來，越來越多研究是使用方向性凝固來進行，其如此受歡迎的主要原因有可以藉此來探討凝固偏析的行為，因為在方向性凝固中其枝蔓晶會長大許多這會有利於我們進行分析，而另一個原因則是方向性凝固常被利用來改善材料的顯微組織，並希望藉此改善其機械性質
，特別是在共晶材料裡，一般利用共晶材料來進行方向性凝固我們可以得到in suit的複合材料其通常具有良好熱穩定性及機械性質，也因此方向性凝固通常被利用來製造良好排列及細小散佈相的結構。
本實驗主要是去探討方向性凝固中溫度梯度、拉伸速率及化學成分調節對材料顯微結構的影響。在A356鋁合金及其添加1wt. % Mn的合金裡我們可以明顯發現其Al的枝蔓晶比一般自然冷卻的顯微組織要大的很多，這有利於我們去進行定量分析。而改變拉伸速率對其枝蔓晶方向的影響我們可以藉由A356鋁合金來探討，在A356鋁合金降低拉伸速率可發現枝蔓晶的方向會逐漸平行熱流，但再添加1wt % Mn時則較沒有規則，另外降低速率時我們也可以發現Si的析出相會由板狀轉換成球狀。而添加1wt % Mn時我們主要可以發現白色針狀的Al5FeSi會轉換成白色碎布狀的Al15(Fe,Mn)3Si2。
另外本實驗也對Al-Si共晶合金及Al-Si-Cu共晶合金進行方向性凝固研究，由於目前實驗所設溫度梯度，我們得到的顯微組織結構並不如預期，其推測最主要的原因為溫度梯度太小，造成其冷卻速率過低產生類似時效行為。

Directional solidification technique applied to investigate the dendrite alloy segregation and the phase identification in multiple phases co-precipitation. Because the large size dendrite could form in directional solidification which would provide large scale to investigate the dendrite segregation from dendrite center region to edge region. For the eutectic type alloys, several phases formed together and have the difficulty to identify these fine phases. These alloys could solidify under slower directional solidification condition and form larger phase.

A356 aluminum alloy and add 1 wt.%Mn alloy were applied in this study. The influence of thermal gradient, extruding rate and chemical composition to microstructure were investigated. In A356 aluminum alloy and it add 1wt.% Mn we found the Al dendrite is larger than nature cooling then it is good to carry out quantitative analysis, we also can find the Al dendrite grow paralleled with heat in A356 but not in A356 with 1wt.% Mn, and the precipitate will convert to fibrous from plates when the extruding rate reduced. When A356 alloy addition 1 wt.% Mn the Al5FeSi IMC would convert to Al15(Fe,Mn)3Si2.

We also take Al-Si and Al-Si-Cu eutectic system, due to the current temperature parameter, the microstructure is not as expected. Because the
lower thermal gradient caused the lower cooling rate, and generated ageing behavior. Thus the change of extruding rate is not affecting the microstructure.

論文審查書 i
致謝 ii
中文摘要 iii
英文摘要 v
目錄 vi
表目錄 viii
圖目錄 ix
一、 前言 1
1-1 研究背景 1
1-2 研究動機 2
二、 文獻回顧 3
2-1 Al-Si系鋁合金簡介 3
2-1-1 化學成分調節對亞共晶系之Al-Si系鋁合金的影響 3
2-1-2 冷卻速率對顯微組織的影響 5
2-1-3 Al-Si共晶組織的成核成長 6
2-2 凝固理論 6
2-2-1 金屬凝固 7
2-2-2 方向性凝固 7
2-3 共晶合金的方向性凝固 8
三、研究方法與步驟 10
3-1研究方法 10
3-2實驗步驟 10
3-2-1合金試片準備 10
3-2-2方向性凝固實驗設計 12
3-2-3 試片分析 12
四、實驗結果與討論 13
4-1 STA分析 13
4-2-1 A356鋁合金之方向性凝固組織 14
4-2-2 A356鋁合金添加1wt. % Mn之方向性凝固組織 15
4-2-3 Al-Si共晶合金之方向性凝固組織 15
4-2-4 Al-Si-Cu共晶合金之方向性凝固組織 17
4-3 定量分析 18
4-4 A356鋁合金凝固偏析分析 18
五、結論 20
六、參考文獻 22

表目錄
表2-1 A356鋁合金成分表 (開南金屬工業股份有限公司) 28
表2-2 Al-Si-Cu之Invariant Equilibria 28
表4-1 各組試片之STA分析與實際量測溫度 29
表4-2 圖片4-33之定量分析結果 29
表4-3 圖片4-34之定量分析結果 30
表4-4 圖片4-35之定量分析結果 30
表4-5 圖片4-36之定量分析結果 31
表4-6 圖片4-37之定量分析結果 31
表4-7 圖4-38的定量分析結果 32
表4-8 圖4-39的定量分析結果 33
表4-9 圖4-40的定量分析結果 34

圖目錄
圖2-1 Al-Si二元相圖[3] 35
圖2-2 Al-Si-Cu三元相圖[3] 35
圖2-3 亞共晶系之Al-Si合金的共晶Si型態比較(a) 未調節 (b) 添加Sr(300 ppm Sr) (c) 添加Sb (2400ppm Sb)[6] 36
圖2-4 Al-Fe二元相圖[3] 36
圖2-5 Al-5%Si-1%Cu-0.5%Mg-(Fe)合金之各種常見的含鐵介金屬相 (a) β-Al5FeSi platelets (b) script-like α-Al8Fe2Si (c) π相(Al8FeMg3Si3) 從β長出 (d) script-like π相[8] 37
圖2-6 Al-7%Si-0.2

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