|About this Abstract
||2011 TMS Annual Meeting & Exhibition
||Bulk Metallic Glasses VIII
||Nanoscale Mechanics and Medium Range Order in Bulk Metallic Glasses
||Don S Stone, Zenon Humberto Melgarejo, Jinwoo Hwang, Jon B Puthoff, Joseph E Jakes, Hongbo Cao, Chuan Zhang, Eren Kalay, Matthew J Kramer, Paul M Voyles
|On-Site Speaker (Planned)
||Don S Stone
Broadband nanoindentation creep (BNC) measures hardness of Cu-Zr and Cu-Zr-Al metallic glasses across 5-6 decades in deformation rate. The experiments generate activation volume data across a wide enough range of flow stress to test atomistic theories of plastic deformation and to detect subtle differences in behavior depending on composition and annealing. For instance, BNC-based estimates place the shear transformation zone (STZ) size at between about 150 and 600 atoms, depending on composition, which falls in the regime of medium range order (MRO). Additional information about MRO is gained from fluctuation electron microscopy (FEM), which reveals the “graininess” of the structure at nanometer length scales. FEM experiments demonstrate an ordering length scale of 1.7-2.5 nm in Zr-Cu metallic glass. Annealing experiments demonstrate quantitatively the structural relaxation of our metallic glass samples including an increase in STZ size.