Understanding aging in metallic glasses at the atomic scale

V.M. Giordano(team (nano)materials for energy), in collaboration with a colleague from ESRF, has published an article entitled «Unveiling the structural arrangements responsible for the atomic dynamics in metallic glasses during physical aging» in the journal Nature Communications. This article has been highlighted by the INP.

Despite their outstanding mechanical and elastic properties, the widespread use of metallic lasses is at this day still limited by their intrinsic out-of-equilibrium nature, giving raise to irreversible phenomena like ageing. A microscopic understanding of ageing is fundamental for better controlling the glasses properties and ultimately designs new more stable amorphous materials. The two authors haves combined advanced synchrotron radiation techniques for directly connecting, for the first time, atomic structural rearrangements and atomic motion in a hyper-quenched metallic glass, during successive annealing. This approach has allowed them to gain insight into the microscopic origin of the different ageing regimes recently reported in these glasses. glasses at the atomic level, such as a peculiar fast ageing. This process appears related to atomic rearrangements aiming to release internal residual stresses, giving rise to a cascade mechanism of relaxation. When these stresses are released, ageing at the atomic scale abruptly stops (while macroscopically the system is still aging), and the atomic rearrangements do not affect density but increase the medium range order, ultimately preparing crystallization. The transition between the two ageing regimes is probably at the origin of a ductile-to-brittle transition.

28/02/2016