Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 38: Liquid and Amorphous Metals
MM 38.4: Vortrag
Mittwoch, 28. März 2012, 15:45–16:00, H 1029
A model for superplastic deformation of metallic glasses — •Jonas Bünz1, Gerhard Wilde1, and K. Anantha Padmanabhan2 — 1Institut für Materialphysik, WWU Münster — 2University of Hyderabad
The deformation behaviour of bulk metallic glasses is different from that of crystalline materials in that no restriction is placed on it that the displacement vector should be relared to the lattice parameter. Applied stresses get localized, lead to shear band formation and cause catastrophic failure after little or no plastic strain. In the supercooled liquid region, however, bulk metallic glasses can experience large strains; even superplasticity. We present a model for superplastic deformation of bulk metallic glasses, subjected to deformation in the supercooled liquid region. The model is based on the formation of shear transformation zones on a microscopic scale and the consequential development of mesoscopic glide planes of several nm. The model has been validated using experimental stress / strain rate data petaining to eight different glassy systems and is able to estimate the experimental strain rates within a factor of two. Based on this analysis the activation energy for rate controlling deformation and the threshold stress needed for the onset of interfacial sliding can be determined. Comparison with results obtained through other measurements reveals that the deductions based on the model are physically very meaningful.