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|Authors: ||黃泳鋒;Huang, Yong-Fong|
|Keywords: ||摩擦攪拌固相積層製造;電子背向散射繞射分;織構分析;材料流動;機械性質;最佳製程參數表;Friction Stir Additive Manufacturing;Electron Back-Scattered Diffraction;texture analysis;materials flow;mechanical properties;parameter window|
|Issue Date: ||2019-05-23 12:52:44 (UTC+8)|
|Abstract: ||近年來，工業快速發展對能源消耗不斷增加，導致地球上的資源正在急遽銳減當中。節能減碳的綠色製造議題為近年機械工程研究趨勢指標，而許多航太應用之鋁基元件為複雜結構，其加工過程中費時與廢料且耗能對地球與環境極不友善，為了得到低成本之精細且均勻的複雜結構，所以航空、航太產業致力於新興3D積層製造技術的發展。積層製造技術(Additive Manufacturing, AM)其製造時由3D模型數據來堆積材料使物體成形的方法，有別於減法加工，是以逐層添加材料製造元件。但傳統金屬積層製造仍有積層速率、積層材料性質、積層體積與積層成本等待突破的重點。若以較新穎之技術:摩擦攪拌固相積層製造(Friction Stir Additive Manufacturing, FSAM)，將以固態積層之方式將材料堆疊成所需幾何形狀，不僅製備鋁鎂輕合金相變問題，也能有效避免積層材料內部孔隙與凝固缺陷，使積層材有優越之機械性質。本研究以耐腐蝕性優良且烤漆後強度較高之析出硬化型6系鋁合金作為底板，以晶粒細化型5系鋁合金作為補強肋，利用連續堆疊的方式製備T型結構件。探討其積層區材料流動現象，並測試其機械性質，最後以電子背向散射繞射分析其微結構與機械性質之關係，以闡述其強化機理。目前金相觀察顯示有鉤狀結構(hook)的產生，但是由於其並沒有蔓延入積層區，故不會影響積層材性質。硬度試驗結果顯示積層材硬度值由底部向頂部降低，且道次重疊區域會因重複攪拌而使其硬度降低。利用電子背向散射繞射分析可得知，於較高層數區域內有更好的晶粒細化效果，而底部區域會因製程中往覆的熱循環影響，使其發生類似於退火的現象，使其晶粒粗化。而Kernel average misorientation 分析發現，底部區域其再結晶比例較高，而道次重疊區域經重複攪拌後，亦能提高其再結晶比例。為了優化積層材其機械性質或製備功能梯度材料，繪製出摩擦攪拌固相積層製程參數範圍，利用積層區寬度、hook影響寬度與積層區平均硬度量化其積層區特性。由橫截面金相可發現當熱輸入量不足時，會因材料流動不及而導致缺陷的發生。且後退邊hook將會沿著接合線水平蔓延入積層區，隨著單位熱輸入量的增加，其鉤狀結構隨著熱機影響區生長的現象愈趨明顯。積層區平均硬度可得知，Al6061-T651若參數選擇適當，經製程後最高則可達105HV約為母材95%之硬度值。Al5052-H32經製程後則為65HV約為母材81%之硬度值，且可發現單位熱輸入量對其硬度趨勢並無太大影響。|
In recently year, the green manufacturing issue of energy conservation and carbon reduction is a trend indicator of mechanical engineering. However, many aluminum-based components for aerospace applications are complex structures. In order to obtain a low-cost, fine and uniform complex structure, the aerospace industries are committed to the development of 3D additive manufacturing technologies.Additive manufacturing (AM), defined as the process of joining materials to make objects from 3D model data, is a new generation of manufacturing processes in which some parts are fabricated by layer-by-layer addition of materials as opposed to traditional subtractive manufacturing methodologies. For the traditional metal-based additive technologies still have some specific characteristics waiting for breakthrough such as build rate, build volume, material properties and build cost. Friction stir additive manufacturing (FSAM), as a new environmentally friendly, energy-effective solid-state process technology. In FSAM process, the metal substrates such as aluminum/magnesium alloys are being processed but do not melt and recast, which can avoid efficiently some internal porosities and solidification defects.This research reports a solid state FSAM for producing a T-stringer structure. Grain refinement alloy 5052 and precipitation hardening alloys 6061 are chosen for similar and dissimilar material stacking. The macro-flow characteristics and mechanical properties of the laminated zone are studied. The microstructure evolution and recrystallization was also investigated using optical microscope (OM) and electron backscatter diffraction (EBSD).The transverse macrograph of FSAM specimen showing the hook characteristics, but it does spread into the laminated zone. Hardness test shows the hardness of the laminated zone decreases from the bottom to the top, and the hardness in the overlapped region is reduced by double stirring. EBSD analysis shows significant grain refinement in the additive zone of higher stacking layer. Due to the repeatable heat generation, the bottom region causes a phenomenon similar to annealing to coarsen the grains. Kernel average misorientation (KAM) analysis, the bottom region and overlap region have higher recrystallization ratio.To optimized the mechanical properties of the laminated materials or prepare the functionally graded materials. The parameter window of friction stir additive manufacturing was made. The characteristics of the laminated zone are quantified by using the width of the laminated zone, the width of the hook and the average hardness of the laminated zone. The macrograph shows that when the heat input is insufficient the defect occur and the hook spread horizontally into the laminated zone. Hardness test reveals that Al6061-T651 has a maximum hardness value 105HV which is about 95% of the base metal. Al5052-H32 is about 81% of the base metal and the unit heat does not have much influence on hardness distribution.
|Appears in Collections:||[機械工程學系] 學位論文|
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