Synthesis, microstructure, and deformation mechanisms of CuZr-based bulk metallic glass composites

.............................................................................................................................................V Kurzfassung.....................................................................................................................................IX 1 Theoretical background ........................................................................................................ 1 1.1 Development of metallic glasses.................................................................................... 1 1.2 Formation of metallic glasses.......................................................................................... 3 1.2.1 Thermodynamic considerations............................................................................ 5 1.2.2 Kinetic considerations............................................................................................... 7 1.2.3 Structural considerations.......................................................................................10 1.3 Mechanical properties of metallic glasses................................................................14 1.4 Deformation mechanisms of metallic glasses.........................................................18 1.4.1 Shear transformation zone theory......................................................................18 1.4.2 Free volume model ...................................................................................................20 1.4.3 Potential energy landscape theory.....................................................................21 1.4.4 Cooperative Shearing Model .................................................................................22 1.5 Strategies to improve the ductility of metallic glasses........................................24 1.5.1 Nano-scaled microstructural inhomogeneities .............................................25 1.5.2 Micro-scaled microstructural inhomogeneities ............................................28 1.5.3 CuZr-based BMG composites ................................................................................31 2 Experimental techniques ....................................................................................................37 2.1 Sample preparation ..........................................................................................................37 2.1.1 Arc melting/suction casting ..................................................................................37 2.1.2 Centrifugal casting ....................................................................................................38 2.1.3 High-frequency melting/injection casting.......................................................39 2.1.4 Melt spinning...............................................................................................................39 2.1.5 Ball milling and powder consolidation .............................................................40 2.2 Structure characterizations ...........................................................................................41 2.2.1 X-ray diffraction.........................................................................................................41 2.2.2 Optical microscopy and scanning electron microscopy.............................41 2.2.3 Transmission electron microscopy ....................................................................