题　目：Quantitative size effects in the mechanical response of metallic glasses probed through in-situ bending and compression

报告人：Changqiang Chen（陈常强）
　　　　　　Department of Applied Physics, Materials Innovation Institute,
　　　　　　University of Groningen, The Netherlands

时　间：1月15日（周五）9:30-11:00

地　点：李薰楼468室

Welcome to attend!

 

ABstract

Understanding and controlling shear localization in metallic glasses (MGs), especially with respect to the process by which shear bands accumulate in a specific microscopic location and propagate, both spatially and temporally, is one of the major tasks in the research of metallic glasses. Study of the deformation behavior of small volume metallic glass is an interesting route for the exploration of shear localization in MGs and is the topic of this presentation.

Quantitative bending and compression tests on tapered and taper-less micro-/nano- pillars made of two amorphous alloys were performed in-situ in a Transmission Electron Microscope (TEM). Under microcompression each pillar shows an intermittent plastic flow accommodated by inhomogeneous shear banding. However, the individual shear banding events are strongly size-dependent, i.e. in larger pillars the deformation is controlled by nucleation of shear bands, but in smaller pillars it becomes propagation controlled. On the other hand, the yield stress is essentially size-independent. Microbending tests show further advantages by amplifying size effects and minimizing artifacts. An interesting finding is that by microbending, a switch from highly inhomogeneous to fully homogeneous deformation is observed at an experimentally accessible size regime near 200 nm, whereas it is not accessible under microcompression even not at sub-100 nm scale. These size effects are well interpreted by a micromechanical model, leading to a deformation map in the stress-size space. A physical picture of nanoscale shear localization process is provided.

About Dr. Changqiang Chen

Changqiang Chen graduated from Nanjing University of Science and Technology with a Bachelor degree in 1998. Afterwards, he came to Institute of Metal Research, CAS, and became a PhD candidate working in Division of Materials Fatigue and Fracture of Shenyang National Lab for Materials Science. He got his PhD degree in Materials Physics and Chemistry in 2004. He continued thereafter his research in Tsinghua University, National Center of Electron Microscopy as a postdoctoral researcher before he moved to University of Groningen, the Netherlands, in Jan. 2007, where he worked till now.　

Dr Chen’s research is mainly on the structure and mechanical properties, and deformation physics of advanced materials and structures, either in bulk form or in the form of small volumes. Many of his efforts have been put on underlying micro-/nano- structures probed by transmission electron microscopy (high resolution and analytical TEM). He has been working on material systems like coarse-grained and nanostructured metals, amorphous alloys, multilayers, nanocomposite films, nanowires/tubes, and so on. He has a number of publications on peer reviewed scientific journals like, Phys. Rev. Lett, Appl. Phys. Lett., Acta Mater, Nanotechnology etc. His work has been cited for more than 220 times so far.

He is a recipient of the "ChangXu Shi" award (rank 1, 2004) from Institute of Metal Research, Chinese Academy of Sciences. His work on "Mechanical properties of ZnO nanowires" was nominated for Top 10 Breakthroughs in Chinese Fundamental Research by Ministry of Science and Technology of China, 2007. And he was awarded the “Prize of Outstanding Reviewer for Scripta Materialia” by Acta Materialia Inc., Elsevier, May, 2009.