报告题目：

Atomic-scale characterization of shear bands in metallic glasses: tracer diffusion, free volume and nanocrystal development

报告人:             Prof. Gerhard Wilde

University of Münster, Institute of Materials Physics, Münster, Germany                     

时间：2014年11月24日(周一)   10:00

地点：中国科学院力学研究所主楼344会议室

报告摘要：

Deformation in glasses proceeds differently than in crystalline materials due to the absence of defined lattice planes and due to the absence of line defects with discrete Burgers vectors. Experiments have shown that deformation exceeding the elastic range is mostly localized in plate-like mesoscopic defects, so-called shear bands. Although the occurrence of shear bands during plastic deformation of metallic glasses is well known, their actual physical properties remain fairly unknown. Here, experimental data on the rate of atomic diffusion within shear bands has been obtained using the radiotracer method on post-deformed specimens. The experimental results indicate unambiguously that the diffusivity is largely enhanced as compared to volume diffusion in the same metallic glass at identical temperatures. This result is also discussed with respect to nanocrystal formation in shear bands.

In order to analyze the local properties of glassy matter within the shear band regions, a new approach based on analytical transmission electron microscopy methods has been developed. In fact, this approach allows to quantitatively determine the local mass density, composition and structural states with nanometer resolution. Thus, shear bands and the surrounding matrix can be analyzed separately and comparatively. In addition, to analyze the shear band propagation and interaction on a mesoscopic scale, digital image correlation in combination with the application of nanoscale marker patterns and scanning electron microscopy detection have been utilized. For further property characterization, low-temperature heat capacity measurements that measure the Boson-peak contribution have also been performed on as-quenched, deformed and partially relaxed samples. The experimental results are discussed with respect to the underlying mechanism during the early stages of shear band activation and on the properties characterizing these “defects” in deformed metallic glasses.

报告人简介：

Scientific Career

2001-2004  Emmy-Noether Fellowship of the DFG, Research Center Karlsruhe and University of the Saarland

2004-2006  Group leader, Research Center Karlsruhe and Full Professor (W2) at University of the Saarland

Since 2006   University Professor W3 (University of Münster); Director of the Institute of Materials Physics

Since 2007   Scientific Member of the Center of Nanotechnology (CeNTech), Münster.

Since 2013   Member of the Rectorat’s Commission on Internationalization

Since 2013   Permanent Member of the Board of Reviewers of the DAAD

 Scientific Output

> 240 scientific publications , > 2800 citations, h = 32 (Scopus) , > 400 conference contributions , >145 invited lectures for scientific colloquia (incl. plenary- keynote and invited lectures at international conferences including TMS, MRS and different conference series) , Host for > 10 Humboldt fellows, 2 Humboldt research prize winners, 1 Mercator Professor

报告联系人：沈楠  (office@lnm.imech.ac.cn 82543935)