http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/35 2026-04-04T23:35:36Z http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/46585 標題: 黃銅退火雙晶與高碳麻田散鐵相變雙晶之奈米顯微組織研究; Studies on nanostructure for annealing twin in α-brass and transformation twin in high-carbonic martensite 作者: Hsin-Yi Lee; 李欣怡 摘要: 退火雙晶經常發生在f.c.c金屬或合金中，它是由於在再結晶成長的過程中，偶發的堆疊錯誤所造成的。因此，退火雙晶對材料機械性質的影響甚是重要。我們需要更加地了解退火雙晶的晶界與一般晶粒的晶界對強度的貢獻是否有差異。本實驗的硬度量測顯示雙晶晶界的平均硬度值比一般晶粒晶界的平均硬度值僅稍微低了5Hv。而且從TEM的圖片也可以看出雙晶晶界除了有橫滑移的現象產生外，也可以阻擋差排的滑移，並在晶界上產生階梯狀的凸起。此階梯狀的凸起可視為差排在雙晶晶界上分解的證據。由於差排在雙晶晶界上分解是能量不利的，且分解後的差排可留在晶界上合併釋放，因此致使雙晶晶界的存在可維持一定的強度和極優異的韌性。所以，雙晶的密度也是影響機械性質的另一個重要因素。我們做一連串不同溫度的熱處理去量測雙晶的密度。發現雙晶的密度跟晶粒的大小成正比。這個結果符合Pande所提出的經驗式：N=Kt ln(D/ D0)。本實驗以C2600黃銅(α-brass)為材料量測到Kt值接近0.3。 相變雙晶通常是為了維持麻田散鐵相變時所需的非均質晶格不變應變而形成的。板片狀麻田散鐵最特殊的特徵就是在中心由非常高密度的相變雙晶所組成的中脊面區域。中脊面從以前就被視為是相變最先產生的區域，但相關文獻卻不太普及。因此，本實驗利用DSC實驗及TEM觀察thin plate和lenticular麻田散鐵內部中脊面的細部特徵以及它最初的形貌。由DSC實驗和試片在液態氮中經由不同時間的深冷處理觀察到thin plate麻田散鐵比lenticular麻田散鐵先形成。因此，我們可以推斷thin plate麻田散鐵可以轉變為lenticular麻田散鐵。TEM照片顯示thin plate麻田散鐵內佈滿了跨越整個板片的雙晶，而lenticular麻田散鐵則是由中脊區、雙晶擴展區和非雙晶區所組成。所以，前者是藉由雙晶來達到晶格不變應變，而後者是同時藉由雙晶和滑移兩種形式來達到麻田散鐵相變所需維持的晶格不變應變。此外，在回火實驗中觀察到由許多密集雙晶所構成的中脊區域提供了碳化物最有利的析出位置。且由回火後麻田散鐵內的基地在中脊區域有一小角度的旋轉，可推測中脊區為一高應力集中區，回火後會在此產生應力釋放使得中脊區的兩旁晶格有一個小角度的旋轉。高碳高鉻的不鏽鋼合金在600˚C回火0.5 ~ 2小時先產生M3C碳化物而後再形成M23C6碳化物。實驗發現前者和麻田散鐵基地維持Bagaryatsky方位關係，後者則接近Kurdjumov-Sashs方位關係。; Annealing twins usually form as a consequence of growth accidents or are presumed to form on stacking faults during the recrystallization of fcc metals and alloys. Therefore, the effects of annealing twins on mechanical properties are very important. It is desirable to determine the difference in strength contributions between general grain and twin boundaries. The results of hardness measurements have shown that the hardness of the twin boundary is a little lower (about 5Hv) than that of the general grain boundary. TEM micrographs indicated that slip lines can penetrate twin boundaries by cross-slip, or if obstructed, form ledges at the twin boundaries. The observations of the ledges at twin boundaries provided evidence for the dislocation dissociations. The energetically unfavorable dissociated reactions and the coalescent partial dislocations released at the twin boundary contribute to the maintained strength and excellent ductility of the twin boundaries. Additionally, a series of annealing treatments at different temperatures were carried out to measure twin density. The results show that annealing twin density depends on grain size. Pande's experiential equation for calculating the annealing twin density (N=Kt ln(D/ D0)) agrees well with our experimental results. The material depending value (Kt value) in Pande's experiential equation for C2600 brass was measured at about 0.3. Transformation twins usually form in the high carbonic martensite transformation to maintain the inhomogeneous lattice - invariant. A typical characteristic of lenticular martensites is the appearance of an obvious high density twinned region (i.e., a midrib region). The midrib is considered to be the region where martensite transformation starts. In this work, it has been found that thin-plate and lenticular martensites co-existed in the specimens of Fe-1C-17Cr stainless steel. The substructures of thin plate martensites and lenticular martensites were examined using TEM, focusing on the details of the midrib region. The results of the DSC experiment and the course of the isothermal holding in the liquid nitrogen (-196˚C) indicated that the thin plate martensite formed first and lenticular martensite later. These results provide evidence to suggest that thin plate martensite can be transformed into lenticular martensite. Transmission electron microscopy revealed that thin plate martensite is composed of a set of internal transformation {112} twins crossing through the interior plate, while the lenticular martensite contained three subzones: the midrib region, extended twinned region, and untwinned region. The results obtained from TEM observations suggest that the transformations of thin plate martensite and lenticular martensite are initiated at the same midrib region. During the growth, the former keeps the lattice-invariant deformation mode of twinning, whereas the latter combines both twinning and slip modes. Additionally, the result of tempering experiments indicated that the midrib region of the martensite contained a large amount of twinned boundaries, which is the preferential position for carbide precipitations. TEM observation showed that tempering treatment resulted in the release of stress at the midrib region, i.e., the stress-concentrated region, and caused the martensite crystal to rotate slightly. TEM results indicated that M3C type carbide was dominant after tempering at 600˚C for 0.5 hours, but M23C6 type carbides was frequent after tempering for 1 and 2 hours. Analysis of diffraction patterns revealed that in this Fe-1C-17Cr alloy, Bagaryatsky OR was found between ferrite and M3C carbide, and Kurdjumov-Sashs OR was found between ferrite and M23C6 carbide. 2010-01-01T00:00:00Z http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/6691 標題: 黃銅退火雙晶與機械雙晶之顯微組織研究; Studies on Microstructure of Annealing Twin and Deformation Twin in α-brass 作者: I-Cheng Chang; 張以澄 摘要: 雙晶是指材料中兩個晶體其方位具有鏡面對稱關係。此論文將針對以下兩種型態的雙晶加以討論：退火雙晶發生在退火時再結晶成長過程中，偶發的堆疊錯誤造成，而機械雙晶則是當基地受到應力應變，為了減少系統總能而產生。較早期的文獻認為機械雙晶僅僅發生在體心立方晶體內，但近期的實驗證明面心立方晶體中不僅有退火雙晶，也可能產生機械雙晶；因此，此篇論文中將介紹較廣為接受的理論及模型來解釋退火雙晶以及機械雙晶的生成原因。 由於雙晶晶界是由Shockley 部分差排以及疊差生成，在某些情況下可以阻礙差排的前進，其往往被視為增強材料機械性質的要素之一；但有時候在雙晶介面附近會有差排滑移現象，因此雙晶材料的延展性可比其他加工硬化材料來得佳。若雙晶晶界附近產生滑移，差排分解成部分差排，則僅有特定方向的部分差排可以繼續往前滑動，晶界會阻礙剩下的差排，因此晶界處會有階梯狀特徵。實驗中我們將以光學顯微鏡以及穿透式電子顯微鏡來觀察退火雙晶、機械雙晶、階梯狀特徵、滑移現象。 此外，本實驗也以電子背向散射繞射儀進行退火雙晶結晶面方位分析，同時以矩陣來計算晶體之間的misorientation；最後利用電子背向散射繞射的結果，施打不同方位的結晶面硬度，以及不同結晶面之間的雙晶晶界硬度。; The term of twin in materials represents two crystals with a mirror symmetry relationship. In this thesis, two types of twins will be discussed: one is the annealing twin, and the other is the deformation twin. The formation of annealing twin, as a result of annealing treatment, can be traced back to growth accidents or stacking faults during recrystallization. The deformation twin, on the other hand, is the accommodation to the deformation in matrix owing to the energy minimums. Additionally, some previous studies show that not only in BCC materials but also in FCC materials do deformation twins exist. Some conceivable models and mechanisms will be presented for the formation of annealing twins and deformation twins. The twin boundary, formed by Shockley partial dislocations and stacking faults, is believed to enhance the mechanical property of materials because it can obstruct the movement of dislocations; therefore, the interaction of them and the incoming dislocations are noticeable. However, not every twin boundary will hinder the dislocation; unlike other strengthening method, the existence of twin boundary will improve the ductility. Some of dislocations may cross-slip at the twin boundary, and thus the ductility is maintained. One of the trace of cross-slipping is the ledge of twin. When dislocation dissociates into Shockley partials, only part of incoherent twin boundary can glide continuously, while the other part stops and forms a “step” on boundary. In this thesis, the morphology of annealing twin, deformation twin, the ledge, cross-slipping will be shown by optical microscopy and transmission electron microscopy. Besides, the orientation of annealing twins will be manifested by EBSD, and the identification of misorientation will be identified by orientation matrices. The result of EBSD will be used in the hardness test, which considers the effect of twin boundary in different orientation. 2012-01-01T00:00:00Z http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/79851 標題: 麻時效鋼 Custom 475 之相變態與晶體學研究; Study on Transformation Crystallography in Custom 475 Maraging Steel 作者: Cheng-Yao Huang; 黃正堯; f05527001 摘要: " 本研究旨在探討低碳麻時效鋼 Custom 475 的相變態與晶體學性質。為了揭露其原沃斯田鐵於高溫時之結構，本研究開發出一全新的演算法「Gamma OR 1.0」來針對母相相位重構運算。該重構方法由三個步驟所組成：(1) 方位關係精煉 (2) 方位整併 (3) 區域投票。此程式可藉由讀取電子背向繞射的原始資料來決定出最有可能的高精度母相方位，而其重構結果則藉由包含有殘留沃斯田鐵的原始資料來驗證。藉著適當選擇用於母相相位重構的參數，亦可達到低誤判率與更好的計算效率。本演算法已與商用的電子背向繞射資料分析軟體做整併，並將於近期上市發佈。 然而，Gamma OR 1.0在形變後的沃斯田鐵數據之運算結果並不理想。為了進一步研究熱壓後的Custom 475 之母相資訊，「Gamma OR 2.0」因而被發展出來。與1.0版本不同的是，此新演算法藉著邊界投票的方式來強化麻田散鐵的次條束塊(sub-block)邊界上之計算靈敏度。從結果可展現出熱壓過程中再結晶沃斯田鐵與雙晶介面崩塌的資訊。除此之外，2.0版本也在雙晶晶界上有更好的重購品質。總的來說，Gamma OR 2.0 可以在更通用的情況下提供更全面的重構結果。 接著，本研究探討在不同原沃斯田鐵晶粒大小與不同形變量的影響下，其變體選擇現象的差異。結果顯示，原沃斯田鐵的晶粒尺寸對方位關係並沒有影響。而當原沃斯田鐵的晶粒尺寸足夠小(＜10 微米)或是施加足夠大的應變(～50%)時，僅有較少的包束(packet)會產生。至於次條束塊的分布，當原沃斯田鐵晶粒尺寸很小時，僅有一組雙晶類的次條束塊傾向於在同一個包束中生成藉以調適應變。相對的，當原沃斯田鐵晶粒被施加很大的形變後，同一組Bain方位的次條束塊會佔主要地位，這是由於滑移平面做為成核點使特定變體的麻田散鐵相變態。 此外，本研究亦討論Custom 475中的析出物演化過程。結果顯示在熱處理溫度520度且持續4小時的時效條件下，可達到時效峰值600HV。兩種主要的析出物分別為B2相與R相結構。其中，最佳強度的條件是發生在小尺寸(2至5奈米)的B2相與中尺寸(10至20奈米)的R相之組合。更高的時效溫度將會導致沃斯田鐵逆相變及析出物粗化，使硬度降低。而在時效處理前施加熱壓製程的狀況下，高密度的差排則會作為擴散途徑使析出物粗大。另外，本研究亦檢定出R相與麻田散鐵的方位關係為(1 4 -5 0)_R//(1 -1 0)_BCC ,[0001]_R//[111]_BCC。且8個不同方位之變體可在R相自體心立方相中析出時所產生。 " 2021-01-01T00:00:00Z http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/68235 標題: 高阻水氣性之石墨烯/環烯烴共聚物奈米複合膜; Graphene/Cyclic Olefin Copolymer Nanocomposite Films as High-Performance Moisture Barriers 作者: Guo-Cyuan Fang; 方國權 摘要: 阻氣的目的為減少氣體的侵蝕，以達到保存與展現內容物的性質，阻氣的應用非常的廣泛，從食品到電子元件的包裝，尤其近年來，隨著軟性電子元件的發展，使得軟性基板上的阻氣更為受到重視。 石墨烯，為已知中最強韌且最薄的高比表面積之材料，已被應用在各項領域當中，在高分子奈米複材的領域當中，由於單層的石墨烯是完全隔絕氣體，再者，水氣滲透的路徑能被擁有巨大的比表面積之石墨烯拉長，故亦適合做為阻氣的奈米複合材料，以期均勻的分散石墨烯在高分子當中，藉此降低水氣滲透率。 然而石墨烯的片與片之間有著π-π作用力，故容易聚集成多層的石墨烯，因此很難均勻的分散在大部分的介質當中，而聚集的程度將使得奈米複合材料的阻氣性質無法充分的展現，由於目前透過溶液態製程的高分子複材阻氣膜離電子等級的阻氣封裝還有一大段距離，故本研究致力於開發高阻水氣性之石墨烯/環烯烴共聚物奈米複合膜，透過溶劑的選擇與溶液態製程的調控以解決現有技術之問題。 在此研究中，我們系統性的選擇表面能與石墨烯匹配的溶劑作為介質與調控溶液製程的參數，成功地將高濃度(6.25 wt%)石墨烯分散在環烯烃共聚物當中，製備奈米複合膜作為阻氣應用，其水氣滲透率(water vapor transmission rate)達到0.00352(g/m^2·day)，超越現有溶液態製備之薄膜阻水氣性。; Gas barrier has gained much attention in recent year, it dominates a variety of application ranging from food industry to electronic devices as a means of preventing them from moisture and dust to extend the life-time of perishable goods and electronic devices. Graphene is the strongest and thinnest material ever known with ultra-large aspect ratio, and therefore it has been shown to yield greatly enhanced mechanical properties in graphene/polymer nanocomposites. Moreover, it has also been shown that graphene is impermeable to oxygen, water and even helium. The dispersion of graphene elongates the diffusion path of water molecules and thus improves water vapor barrier property. This promises the realization of gas barriers from graphene/polymer nanocomposites, as long as pristine graphene can be uniformly and orderly dispersed in the polymer matrix. However, the strong π-π interactions between pristine graphene sheets make them difficult to disperse in most media, thereby greatly limiting the gas-barrier performance of graphene/polymer nanocomposites. In this study, by systematically testing solvents with various surface properties (including surface energy and Hansen solubility parameter and conditions of the solution blending process. We successfully dispersed pristine graphene uniformly in cyclic olefin copolymer (COC). The result of COC/graphene nanocomposite exhibited low water vapor permeability (0.00276 g·mm/m^2·day·atm) and interesting thermo-mechanical properties. 2017-01-01T00:00:00Z