|About this Abstract
||2011 TMS Annual Meeting & Exhibition
||Bulk Metallic Glasses VIII
||Study of Activation Parameters of Deformation by Broadband Nanoindentation Creep in Structural Relaxed Zr-Cu-Al Bulk Metallic Glasses
||Zenon H. Melgarejo, Joseph E. Jakes, Jonathan Puthoff, Hongbo Cao, Chuan Zhang, Donald S. Stone, Paul M. Voyles
|On-Site Speaker (Planned)
||Zenon H. Melgarejo
Models of plastic deformation in BMGs hypothesize shear transformation zones (STZs) as the elementary units of plastic deformation. Activation energy for shear of an STZ depends on stress; activation parameters should vary systematically with atomic structure including short and medium range order and should be sensitive to composition, quenching rate, and annealing.
In the present work we employ broadband nanoindentation creep (BNC) to characterize activation volume and energy for plastic deformation in Zr-Cu-Al BMGs. BNC measures hardness across 5-6 decades of strain rate, and is therefore capable of mapping out the shape of the activation barrier. BMGs studied include Zr54Cu38Al8, Zr45Cu49Al6, and Zr36Cu58Al6. STZ sizes estimated from activation volume measurements vary between 170 and 600 atoms depending on composition and annealing. Annealing generally increases both activation energy and STZ volume. Structural relaxation of Zr54Cu38Al8 is studied in detail by measuring BNC in specimens annealed in a differential scanning calorimeter (DSC).