Characterization of In-Situ Shear Band Formation in Metallic Glas

The deformation behavior of metallic glasses is very different from crystalline metals; the lack of a dislocation network prohibits large plastic stains to be manifest during the deformation of metallic glasses. Metallic glasses undergo deformation through the formation and propagation of shear bands. The deformation behavior of metallic glasses is also sensitive to stress states exemplified by the formation of a single catastrophic shear band in tension, yet by multiple shear band formation in compression or bending. With the increased focus on metallic glasses as structural materials further characterization of their deformation behavior is warranted. A variety of techniques to characterize and study shear band formation have been employed, yet few quantitative results have been obtained, and there is no widely accepted mechanism for the formation of shear bands, or how atoms rearrange to form crystallites along shear bands formed in compression. Detection techniques range from acoustic emission [Vinogradov and Khonik 2004], in-situ scanning electron microscopy [Li et al. 2003], transmission electron microscopy [Chang et al. 2006; Jiang and Atzmon 2003], xray diffraction (synchrotron) [Ott et al. 2005], and, most recently, electrical characterization [Yang and Liaw 2006]. With the exception of transmission electron microscopy, the above listed techniques cannot accurately discern atomistic structural changes occurring during the deformation process. Thus, the current proposal outlines experiments that will use neutron scattering to probe atomic rearrangement in shear bands in-situ in order to characterize their structure evolution with mechanical stressing. Successful completion of this project will have direct impact on the understanding of shear band formation in metallic glasses, and allow better design and use of metallic glasses in engineering applications. The results will be published in peer reviewed journals and will help researchers at the University of Kentucky seek local and federal funding to establish a strong research team exploiting neutron diffraction to characterize mechanical behavior of advanced nanoscale engineering materials.