Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/9958
標題: On Evolution of Precipitates in AA 6061 T6 Alloy during Thermal cycling and its Mechanical properties
AA6061 T6鋁合金經長時間熱循環之機械性質及其析出物演進過程之研究
作者: 陳志銘
關鍵字: 鋁;AA 6061;熱循環;穿透式電子顯微鏡;析出物;機械性質;thermal cycling;TEM;precipitate;mechanical property
出版社: 材料工程學研究所
摘要: 
本研究主要探究T6處理後之AA 6061鋁合金經60℃熱循環過程其機械性質的表現以及其析出物於熱循環過程之演進。主要之實驗內容與方法分別為:(a)在機械性質測試方面其測試方法選擇硬度實驗(洛氏硬度,HRB)及拉伸試驗;(b)顯微結構分析方面,以穿透式電子顯微鏡(TEM)觀察AA 6061在熱循環過程中其析出物之析出演進過程。
機械性質測試的實驗結果顯示AA 6061 T6鋁合金經60℃熱循環過程後,其硬度值隨著熱循環有不規則起伏變動的現象。有鑑於此現象,另外對AA 6061分別進行70℃與110℃的熱循環之硬度實驗,實驗結果顯示硬度值也有起伏變動的情形產生,但變動的幅度較T6-60℃的實驗結果小。因此經過熱循環的AA 6061鋁合金其機械性質呈現波動起伏的現象,且在不同溫度熱循環有不同的起伏程度,其中以60℃熱循環最為明顯,循環溫度70℃次之,而110℃之熱循環最為平穩。據此實驗結果觀察到隨著熱循環溫度提高,機械性質起伏的程度有較為趨緩的趨勢。
在TEM分析T6-60℃ AA 6061的顯微結構後觀察到:經T6處理完畢(熱循環數0,0 cycle)之微觀組織由對稱短針狀β"相與少量的細長針狀β"相所組成,隨著熱循環數增加(0 ~ 35 cycles),短針狀β"相的數量有逐漸減少,而細長針狀β"相數量及尺寸有逐漸增加的趨勢。在55 cycles 時觀察到已有少量的桿狀β''相析出,55 ~ 90 cycles組織中析出物為短針狀、細長針狀 β"相與桿狀 β''相,其中短針狀的β"相在90 cycles 時數量已經相當稀少。熱循環數進行到100 cycles 時觀察到析出物β相的出現,組織中以細長針狀之β"居多、桿狀β''次之,而β相數量最少。因此AA 6061 T6鋁合金在60℃熱循環中析出物演進程序為:
β" β" + β'' β" + β'' + β
0 ~ 35 cycles 55 ~ 90 cycles 100 cycles

Abstract
The use of aluminum alloy for light vehicle applications has been known. Aluminum panel or automotive body skin is one of the examples. The Al-Mg-Si AA6061 series alloys are promising for mass production in automotive industry in the near future, partly because they can be hardened during paint-curing process. The present paper considers the precipitate's stability and microstructure evolution of aged Al-Mg-Si alloy especially under the circumstance of environmental temperature changing. The schedule for each cycle is that the specimens are staticly held at 60 ± 5℃ for 9 hours, followed by being kept at room temperature for 15 hours. The total cycle lasted until 100 times. Detail transmission electron microscopy (TEM) examinations were performed for the specimens subjected to thermal cycling with different cycle times. The microstructure of T6 AA6061 consists of short needle-shaped β" (length : 5~10 nm) and fine needle-shaped β" (length : 20~40 nm). As the number of thermal cycle increasing to 35, the amounts of shorter β" decreased but amounts of finer β" increased. Some rod-shaped β''(length : 30~70 nm) begin to precipitate at 55 cycles. Precipitates in the specimens of 55 to 90 cycles include short needle-shaped β", finer needle-shaped β" and rod-shaped β''. The β phase can be observed at 100 cycles. Hence, the precipitation sequence during 60℃ thermal cycling in AA6061 T6 alloy is:
Main phase observed: β" β" + β'' β" + β'' + β
Cycles: 0~ 35 55 ~ 90 100
URI: http://hdl.handle.net/11455/9958
Appears in Collections:材料科學與工程學系

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