Structural aspects of deformation defects in bulk metallic glasses
Materials Science and Technology Division, Oak Ridge National Laboratory, USA
报告摘要：Metallic glasses have liquid-like structure without well-defined topological defects like dislocations in metals and alloys. My presentation will address three critical issues related to the mechanical behavior of metallic glasses: (a) Identification of deformation defects in metallic glasses. High energy X-ray diffraction experiment was conducted—using anisotropic pair distribution function—to characterize the size and stress relaxation ability of defects in metallic glasses activated by external stresses; (b) Identification of two local stress relaxation modes that control macroscopic mechanical properties in metallic glasses. Using the defect characterization method based on high energy X-ray diffraction, two different local stress relaxation modes was observed in defect regions, which are responsible for inhomogeneous and homogeneous deformation, respectively; (c) Structural rejuvenation method was developed to improve and recover the compressive plasticity. The microscopic mechanism of structural rejuvenation was unveiled by structural study and molecular dynamics simulation. Our findings are discussed in the context of pre-yield structural excitations, structural relaxation and rejuvenation, as-well as mesoscopic effects of shear banding during plastic flow.
报告人简介：Dr. Yang Tong received his Bachelor and Master in Physics from Central South University in 2007 and 2010, respectively. In 2015, he obtained his PhD in Materials Science and Engineering from the University of Tennessee-Knoxville under the supervision of Prof. Wojciech Dmowski and Prof. Takeshi Egami, in which he utilized in situ and ex situ high energy X-ray diffraction in his studies of deformation behaviors of bulk metallic glasses. After PhD study, Yang joined City University of Hong Kong as a research fellow under the direction of Prof. Ji-Jung Kai, in which he designed high-entropy alloys for applications in extreme environments. He is now a post-doctoral in the Energy Frontier Research Center, Energy Dissipation to Defect Evolution, at Oak Ridge National Laboratory, USA, where he works on the design of next-generation radiation resistant nuclear structural materials. He has published about 30 articles in peer-reviewed journals including but not limited to Science, Acta Materialia, Materials Research Letters, and Journal of Nuclear Materials.