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【百家大讲堂】第312期:先进电子显微学在物理冶金方面的应用

发布日期:2020-01-07

讲座题目:先进电子显微学在物理冶金方面的应用

报 告 人:陈江华

时   间:2020年1月9日(周四)9:00-11:30

地   点:中关村校区5号教学楼502-1

主办单位:研究生院、材料学院

报名方式:登录10bet体育大学微信企业号---第二课堂---课程报名中选择“【百家大讲堂】第312期:先进电子显微学在物理冶金方面的应用”

【主讲人简介】

  湖南大学教授、博士生导师、材料科学与工程学院院长,教育部“长江学者”特聘教授,国家千人计划特聘专家,教育部首批“黄大年式教师团队”负责人,教育部科技委材料学部委员,亚太材料科学院院士,湖南省政协常委。
  陈江华长期从事材料的微结构表征研究和先进电子显微学技术的理论和方法学研究,是国内外知名电子显微镜专家和材料学家。他曾是世界上第一台球差矫正电镜样机的测试研究员,为推动该先进电镜的蓬勃发展作出过实质贡献和建议。曾是欧洲波函数重构(电子全息)技术发展的参与者,回国后在湖南大学建立起有自己特色优势的软件矫正电镜技术平台并成功应用于铝合金微结构测量表征。陈江华在电子显微学理论和技术以及材料研究方面发表过150余篇论文和10项发明专利,其中以第一和通讯作者在Science发表过关于汽车车身用铝合金材料的论文。主持过国家重大仪器研究、“973”研究计划、高铁列车车身材料可靠性和国产化等重大重点科研项目和课题。2016年获“全国优秀科技工作者”称号。担任和曾担任众多全国学术组织的常务理事和国内外学术杂志编委。

 

Dr. Jianghua Chen has engaged in the field of transmission electron microscopy (TEM) for materials science for 35 years and mainly focuses on the development of TEM theories and methods for diffraction and imaging techniques, and on the TEM applications to materials research. Currently, he is the dean of the college of materials science and engineering and the director of the Center for High-Resolution Electron Microscopy (CHREM) at Hunan University, China.  Previously, he worked as a lecturer at Sichuan University for 8 years (1986--1994). Then he had worked in Europe for 14 years. Firstly in Belgium he did his Ph.D study and a postdoc job in the Electron Microscopy Lab at the University of Antwerp (1994--1998). Then in Germany he worked at Research Center Juelich for two years on the world first prototype Cs-corrected TEM. He then worked as a permanent senior scientist of the Netherlands Institute for Metals Research. After 2007, he gradually transferred his position from Holland to China.


Dr. Jianghua Chen established a few theories and methods for accurate and quantitative analysis of diffraction and imaging in TEM, and also developed a few techniques for achieving atomic-resolution imaging in modern TEM. Having mastered the advanced TEM instruments, he demonstrated as a pioneer how to determine the structures of small precipitates in aluminum alloys using quantitative atomic-imaging techniques. Based on the precisely determined precipitate structures, he revealed the quick-bake-hardening mechanism of the automotive AlMgSi alloys at the atomic-scale. Since then he solved many structure problems in metals. 


Dr. Chen holds 10 patents and has published more than 160 papers.  Due to his great contribution to electron microscopy for materials science, he has won many awards including the prestigious Distinguished Scientists Award 2016, granted by China Association for Science and Technology, and the honorable title of Chang Jiang Scholar Professor, granted by China Ministry of Education in 2008.

【讲座信息】

  高强铝合金中尺寸细小的早期强化相的成分、结构以及演变的表征尚存在难度,这一直以来限制着高强铝合金的发展。我们的研究通过采用原子分辨率的透射电镜(TEM)成像技术和第一性原理计算来解决这些问题。近年来,我们研究了大量典型的高强铝合金,例如2xxx系、6xxx系和7xxx系合金,采用了不同的合金成分,并进行了不同的热处10bet体育艺,以便理解“性能-结构-工艺”之间的关系。结合球差矫正的高分辨TEM和球差矫正的扫描TEM(STEM),我们的主要关注点在于重新认识在这些重要的合金中出现的强化相以及阐明过去遗留下来的关于它们的析出行为的争议。我们的研究表明:
  (1) STEM的原子分辨率成像技术可以在原子尺度提供直观的析出相结构模型,但是HRTEM的原子分辨率成像技术具备快速定量的图像模拟分析可能,可以提供超出电镜的分辨率极限精度的精细的析出相结构。这两种技术的结合可以更有效地解决材料科学中的显微结构难题。
  (2) 铝合金中大多数早期析出相的成分和结构都是高度动态的。随着时效的进行,这些动态析出相的形核,成熟和生长通常遵循特定的演变路径,并且有特征的基因骨架来引导它们各自的演变。我们的研究所揭示的精细的析出规律与目前所发表的教科书和文献中的理解非常不同。

 

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 (AlCu, AlCuMg and AlCuLiMg), 6xxx (AlMgSi and AlMgSiCu) and 7xxx (AlZnMg and AlZnMgCu) alloys, with different compositions and with varying thermal processes for understanding their property-structure-process correlations. Using 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 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 in aluminum alloys 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 in our studies are rather different from previous understandings in the textbooks and literatures published thus far.


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