原子級解析七系列鋁合金奈米析出物顯微結構演化之回顧
Other Title
Review on a Atomic-scale Investigation of the Microstructure Evolution of Nanoscale Precipitates in 7xxx Series Aluminium Alloys
Journal
科儀新知
Journal Issue
232
Start Page
9
End Page
25
ISSN
1019-5440
Date Issued
2022-09
Author(s)
Abstract
前瞻性高強度七系列（Al-Zn-Mg-Cu）鋁合金，經由人工時效熱處理衍生出多型態奈米η析出物，透過高解析穿透式電子顯微鏡影像（HR-TEM）與高角度環形偵測器之掃描透射電子顯微鏡影像（Cs-corrected HAADF STEM），進一步解析主要析出相η_1、η_2和η_4之顯微結構。搭配快速傅立葉轉換法與模擬相對應繞射圖譜，可清楚鑑定析出物與鋁合金基地的晶體方位關係。進一步，透過真實原子布局影像，釐清相對應（1120）η_1、（1010）η_2和（0001）η_4晶面上，所呈現zig-zag、sandwiched和six-fold原子排列結構情況。此外，巨觀下，奈米析出物的形貌、尺寸大小與體積百分率可藉由小角度X-ray散射，加以定量分析。微觀角度中，奈米析出物之間的演化，如：GPII zones或多型態奈米η析出物，亦可藉由sympathetic成核成長機制，於第二相AlMn_6界面孕育而出。此外，3D針尖電子顯微鏡影像重構是未來更能進一步點出傳統以二維投影影像的盲點。然而，高端儀器的重裝備，更需搭配良好的試樣準備與後續影像重構的尖端技術，才能為材料晶體結構演化展開下一個序章。
Multi-types of η precipitates are created in the advanced and high-strength 7xxx series (Al-Zn-Mg-Cu) aluminium alloys, subjected to the artificial ageing treatment. Employed high-resolution transmission electron microscopy (HR-TEM) and Cs-corrected high angle annular dark-field scanning transmission electron microscopy (Cs-corrected HAADF STEM), it can further elucidate the microstructures of η precipitates, such as η_1, η_2 and η_4. Furthermore, the orientation relationships between the aluminium matrix and η precipitates are clearly identified by the fast Fourier transform (FFT) diffractogram and the simulated diffraction pattern. In the present work, it has been found that the atomic edge-on configurations of η_1, η_2 and η_4 are characterized as the zigzag, sandwiched and six-fold atomic arrangements, grown on the (1120)η_1, (1010)η_2 and (0001)η_4 planes, respectively. Additionally, the size, morphology and volume fraction of precipitates can be estimated by small-angle X-ray scattering. We also indicate the nucleation of GPII zones and multi-types of η precipitates on the interface of the AlMn_6 second phases. The 3D electron microscopy imaging is presumably to shed light on the 2D microstructures. The beginning of the crystal structure in materials would be supported by the high-end instruments but also the good sample preparation and the cutting-edge image reconstruction.
Type
journal article