Giordano VM, Ruta B. Unveiling the structural arrangements responsible for the atomic dynamics in metallic glasses during physical aging.
Nat Commun 2016;
7:10344. [PMID:
26787443 PMCID:
PMC4735801 DOI:
10.1038/ncomms10344]
[Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 12/03/2015] [Indexed: 12/03/2022] Open
Abstract
Understanding and controlling physical aging, that is, the spontaneous temporal evolution of out-of-equilibrium systems, represents one of the greatest tasks in material science. Recent studies have revealed the existence of a complex atomic motion in metallic glasses, with different aging regimes in contrast with the typical continuous aging observed in macroscopic quantities. By combining dynamical and structural synchrotron techniques, here for the first time we directly connect previously identified microscopic structural mechanisms with the peculiar atomic motion, providing a broader unique view of their complexity. We show that the atomic scale is dominated by the interplay between two processes: rearrangements releasing residual stresses related to a cascade mechanism of relaxation, and medium range ordering processes, which do not affect the local density, likely due to localized relaxations of liquid-like regions. As temperature increases, a surprising additional secondary relaxation process sets in, together with a faster medium range ordering, likely precursors of crystallization.
Glass aging is one of unsolved problems during glass processing and annealing, partly due to the lack of the mechanistic understanding on microscales. Here, the authors show how local stresses and their evolution affect structural relaxation at an atomic level in a metallic glass system.
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