Topic: Universal Parameter to Quantitatively Predict Metallic Glass Properties

Speaker: Professor E. Ma
             Department of Materials Science and Engineering,
             Johns Hopkins University,
             Baltimore, MD 21218, USA

Time: 10:00-11:30, Monday, July 18, 2016

Venue: Room 403, Shi Changxu Building, IMR, CAS

Welcome to attend!

Abstract

Quantitatively correlating the amorphous structure in metallic glasses with their physical properties has been a long-sought goal. Here we introduce “flexibility volume” as a universal indicator of the structural state, to correlate with properties on both atomic and macroscopic levels. The flexibility volume is assessed via atomic vibrations that probe local configurational space and interaction between neighboring atoms, and is defined in a simple form to be measurable both computationally and experimentally. We show that this indicator deterministically predicts the shear modulus, which is at the heart of key properties of metallic glasses. The flexibility volume correlates strongly on the one hand with atomic packing topology, and on the other hand with the activation energy for thermally activated relaxation and the propensity for stress-driven shear transformations. As such, the flexibility volume provides a structural underpinning of the spatial mechanical heterogeneities. The concrete structure-property correlations discovered are robust and prognostic for all metallic glass compositions, processing conditions and length scales. All these advantages advocate flexibility volume as a useful single-parameter indicator, in lieu of the widely cited but ambiguous “free volume”, to bridge the configurational state metallic glass is in with its properties.