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標題: | AA7075系列鋁合金之機械性質與奈米級析出物演化研究 A Study on Mechanical Property and Evolution of nano-scale Precipitates in the AA7075 Series Aluminium Alloys |
作者: | Yo-Ming Pua 潘有銘 |
指導教授: | 楊哲人(Jer-Ren Yang) |
關鍵字: | AA7075鋁合金,回復再時效處理,小角度X-ray散射,穿透式電子顯微鏡-高解析影像,GPI zone,T6時效,η'析出物,η析出物, AA7075 Aluminium alloys,Retrogression and Re-Aging (RRA) treatment,Small Angle X-ray Scattering (SAXS),High Resolution-TEM (HRTEM),GPI zone,T6 aging,η' precipitates,η precipitates, |
出版年 : | 2021 |
學位: | 碩士 |
摘要: | 本研究採用目前強度最高之7系列(Al-Zn-Mg-Cu)鋁合金,以AA7075成分適度添加不同含量之Mn元素,探討七系列鋁合金中前期析出物GPI zone的形成條件,以及於類似退化再時效處理(Retrogression and Re-Aging, RRA)中,各時效階段機械性質與析出物之間的關係。對於前期析出物的研究,藉由in-situ小角度X-ray散射(Small Angle X-ray Scattering, SAXS)鑒定GPI zone的最佳形成條件,並利用穿透式電子顯微鏡(Transmission Electron Microscope, TEM)與硬度試驗,觀察GPI zone其尺寸大小、形貌與分佈於晶粒內部之情況而對材料強度產生的貢獻。而對於探討機械性質與析出物之間的關係,透過拉伸試驗測試不同時效處理條件,如T4、T6、模擬溫成型與最後階段高溫烘烤各階段之機械性質,並利用TEM觀察上述熱處理各階段之顯微結構與統計析出物之尺寸,同時搭配SAXS計算η'與η的體積分率與數量密度,從而分析對機械性質產生影響的主要因素,再結合穿透式電子顯微鏡-高解析影像(High Resolution-TEM, HRTEM)進行析出物的鑒定。 由前期析出物的實驗結果得知最適合GPI zone的生成溫度為90 °C,並且於90 °C持溫10分鐘相比於60 °C持溫30分鐘更有利於GPI zone的生成。此外,不論於[100]或[110]晶帶軸觀察,GPI zone皆為圓形,因此GPI zone的形貌應為球狀。 由析出物的量化實驗結果得知鋁合金的機械強度於T6時效階段達到最高值,模擬溫成型之熱處理階段大幅度下降,而最後的高溫烘烤階段則有所回升。從對應的各項析出物參數之變化結果,可以得知析出物的平均尺寸、η析出物的體積分率、η'析出物與η析出物的數量密度對機械強度沒有直接的影響,而η'析出物的體積分率方為影響機械強度的主要因素。另外,於T6時效階段後的η析出物種類主要為η1與η2。 In this study, the high strength AA7075 Aluminium alloys, combining with proper Mn content, are carried out to investigate the formation condition of early-stage precipitates in 7xxx series Aluminium alloys, GPI zone, and examine the relationship between mechanical properties and precipitates in different aging treatments, which are similar to the retrogression and re-aging treatment. For the study of early stage precipitates, the best formation condition of GPI zone is confirmed by in-situ Small Angle X-ray Scattering (SAXS). The nano-scaled microstructural evolution of the GPI zone is observed by Transmission Electron Microscopy (TEM) for analyzing their influence on hardness. To investigate the relationship between mechanical properties and precipitates, materials are conducted by tensile test to verify the mechanical properties of different aging treatments such as T4, T6 and for molding the warm forming and paint baking processes. During the aging treatment, the evolution of microstructures and statistics of precipitates size is determined by TEM. Furthermore, volume fraction and number density of η' and η precipitates are assisted by SAXS for analyzing the main influencing factor on the mechanical properties. Moreover, the identification of precipitates could be characterized by High Resolution-TEM (HRTEM). According to the results of early-stage precipitates, the optimal generation temperature of the GPI zone is 90 °C, and holding at 90 °C for 10 minutes is more conducive to the generation of the GPI zone than holding at 60 °C for 30 minutes. In addition, the GPI zone is observed to be circle in shape, no matter from [100] or [110] zone axis, so the morphology of GPI zone should be spherical. The results of the quantification part show that the mechanical strength reaches a maximum value at the T6 aging stage, then decreases greatly at the warm forming stage, and rises at the final paint baking stage. From the quantification results of precipitates, it is known that the average size of precipitates, the volume fraction of η precipitates, the number density of η' and η precipitates do not affect the mechanical strength directly. In contrast, the volume fraction of η' precipitates is the main influencing factor on the mechanical properties. The type of η precipitates are mainly η1 and η2 after T6 aging stage. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/49887 |
DOI: | 10.6342/NTU202100625 |
全文授權: | 有償授權 |
顯示於系所單位: | 材料科學與工程學系 |
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