At temperatures well below their glass transition, the deformation properties
of bulk metallic glasses are characterised by a sharp transition from
elasticity to plasticity, a reproducible yield stress, and an approximately
linear decrease of this stress with increasing temperature. In the present work
it shown that when the well known properties of the under-cooled liquid regime,
in terms of the underlying potential energy landscape, are assumed to be also
valid at low temperature, a simple thermal activation model is able to
reproduce the observed onset of macro-scopic yield. At these temperatures, the
thermal accessibility of the complex potential energy landscape is drastically
reduced, and the statistics of extreme value and the phenomenon of kinetic
freezing become important, affecting the spatial heterogeneity of the
irreversible structural transitions mediating the elastic-to-plastic
transition. As the temperature increases and approaches the glass transition
temperature, the theory is able to smoothly transit to the high temperature
deformation regime where plasticity is known to be well described by thermally
activated viscoplastic models.Comment: 43 pages, 9 figures, Appears in Philosophical Magazin
