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Metallic Glasses: Different Deformation Properties Underpinned by the Same Trigger

ORNL Image
Different macroscopic deformation behaviors in metallic glasses originate from the same trigger. Each local minimum in the figure represents a deformation trigger. For materials with different cooling histories, all individual triggers have the same curvature on the potential energy landscape and are thus governed by the same mechanism. The trigger density is very high in the quickly quenched system (front) but low in the better annealed system (back).
A novel simulation approach demonstrates that a universal deformation trigger exists in metallic glasses and that the spatial organization of these triggers is closely related to the dynamics and stabilities of the system. This work demonstrates that a universal trigger initiates deformation and the organization of such triggers significantly affects bulk behavior. This study suggests a manner to manipulate and improve the materials’ mechanical properties, e.g. the ductility, which is a long-standing challenge in metallic glasses.

Atomistic modeling shows that the trigger consists of only a few highly localized atoms. In stark contrast to prior expectations, the size of the trigger is independent of the system’s overall stabilities and mechanical properties. The manners of organization between the triggers are sensitively related to the materials’ processing conditions. The distributions of the triggers are very dense in a system that underwent a fast cooling history, while relatively sparse in a more slowly quenched system. The different organizations of microscopic triggers naturally build up different patterns of potential energy landscapes at larger scales, leading to the different macroscopic properties observed in experiments.

 

Yue Fan, Takuya Iwashita, and Takeshi Egami, “How thermally activated deformation starts in metallic glasses,” Nature Communications 5, 5083 (2014).  DOI:10.1038/ncomms6083

 

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