Microscopic description of plasticity of metallic glasses – experiment and modeling
Abstract: Metallic glasses exhibit very high strength and elastic limit, making them attractive candidates for structural applications. However, they pose a significant challenge as they often undergo work softening, which results in strain localization and macroscopic brittle behavior. Unlike in crystalline materials, the defects that accommodate plasticity in metallic glasses are not well understood, and there is no known mechanism of imaging them. Based on prior work on bubble rafts, these defects, termed shear transformation zones (STZs), are known to be equiaxed clusters of atoms, which undergo shear transformations under stress. Anelastic relaxation provides a powerful tool for exploring STZ properties. We have conducted experiments spanning ten orders of magnitude of time. Combined with modeling, these have enabled us to resolve STZs by the number of atoms they comprise. The insights gained have led to a new level of atomic-scale understanding of plasticity and other atomic transport processes in glasses, and the effect of subtle structural changes induced by thermal treatment.
Bio: Michael Atzmon is Professor in the Departments of Nuclear Engineering and Radiological Sciences and Materials Science and Engineering at the University of Michigan. He is also the faculty advisor of the Engineering Physics undergraduate degree program. Prior to joining the University of Michigan as assistant professor, he was post-doctoral fellow at Harvard University. He received his B.Sc. In Mathematics and Physics at Hebrew University in Jerusalem, and his MS and Ph.D. in Applied Physics at Caltech. Professor Atzmon’s research has focused on basic materials science, including phase transformations and mechanical properties of nanocrystalline and amorphous metals, and radiation effects in metals. He is By-Fellow of Churchill College at the University of Cambridge, UK, and Senior Fellow, Michigan Society of Fellows.