Cryogenic thermal cycling rejuvenation in metallic glasses: Structural and mechanical assessment

Rejuvenation in metallic glasses (MGs) can be achieved by means of thermal cycling treatments at cryogenic temperatures. Here, atomic scale studies were carried out to explore thermal cycling in CuZr MGs at different species contents. Enhanced ductility was observed due to several factors. All samples presented higher potential energy and less-dense structures upon treatments, indicating rejuvenated states. Furthermore, populations of high-centrosymmetric Voronoi polyhedra decreased, while liquid-like structures increased, which are usually related to low rigidity. Atomic connectivity was explored as a measure of the medium range order, revealing that thermal cycling reduced the fraction of 3-atom connections, while increased 2-atom and 4-atom connections. Since 3-atom connections are associated to more-ordered structures, its weakening explains the enhanced plasticity achieved by MGs upon thermal cycling treatments. This study provides new insights into rejuvenation of MGs, delivering atomic scale descriptions at both the short range and medium range order.