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No.165,陈江华教授,9月21日报告

报告题目:The hardening precipitates in high strength aluminum alloys studied by atomic-resolution electron microscopy

  人:陈江华,“长江学者”特聘教授,“千人计划”特聘专家,湖南大学材料科学与工程学院

报告时间:2015年9月21日 下午14:00

报告地点:材料学院A楼308室

  人:曾小勤老师
 
报告人简介:
   陈江华教授1983年毕业于中南大学金属物理专业,后到中科院金属研究所跟随郭可信院士学习电子显微学,获硕士学位。在四川大学从事超硬材料合成研究8年后,到世界著名的比利时安特卫普大学电子显微镜实验室从事博士学位和博士后研究工作。随后到德国Juelich研究中心世界著名电子显微镜实验室做德国自然科学基金会博士后研究员。2000年后成为荷兰Delft理工大学国家高分辨电镜中心核心成员(Staff member)和荷兰皇家金属研究所永久高级研究员,博士生导师。2005年到2006年在中科院物理研究任特聘研究员,入选中科院“引进国外杰出人才(百人计划)”。2006年底加盟湖南大学材料科学与工程学院,任教授,“985工程”首席科学家和院长。2008年获聘材料物理与化学学科教育部“长江学者”特聘教授;2010年获聘国家(千人计划)特聘专家。陈江华长期从事电子显微学的研究工作,在Science,Nature Materials,Acta Materialia等二十多种著名期刊发表论文。
 
报告摘要:
     Developments of high-strength aluminum alloys have always faced a difficult problem: owing to their small size, the early-stage strengthening precipitates are difficult to characterize in terms of composition, structure and evolution. Here we employ atomic-resolution transmission electron microscopy (TEM) imaging and first-principles energy calculations to address these problems. Recent years, we have investigated tens of typical high strength aluminum alloys, such as 2xxx (AlCuMg) and 7xxx (AlZnMgCu) alloys, with different compositions and with varying thermal processes for their property-structure-process correlations. Using advanced aberration-corrected high-resolution TEM (HRTEM) and aberration-corrected scanning TEM (STEM), much of our attention has been paid to revisit the strengthening precipitates in these important alloys and to clarify the controversies left in the past about their precipitation behaviors. Our study demonstrates the followings:
(1)     Atomic-resolution imaging in HAADF-STEM can provide straightforward structure models at the atomic-scale, whereas atomic-resolution imaging in HRTEM with rapid quantitative image simulation analysis can provide the refined structures with high precision beyond the resolution limitation of the microscope. The combination of the two techniques can be more powerful in solving difficult structure problems in materials science.
(2)     Most of the early-stage precipitates are highly dynamic in both composition and structure. Typically, having their characteristic genetic skeletons to guide their evolution, these dynamic precipitates initiate, mature and grow with thermal aging following characteristic evolution paths. The fine precipitation scenarios revealed are rather different from previous understandings in the textbooks and literatures published thus far.
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