Modeling Mechanical Behavior of Amorphous Metals

The mechanisms associated with deformation in an amorphous metal, or a metallic glass, present an interesting topic for research, as it has proven difficult to identify a single process as the underlying mechanism for the observed deformation behavior.  In elucidating the nature of the mechanisms associated with deformation in an amorphous metal, our group employs different modeling techniques to access different length scales.

Molecular statics simulation studies have focused on the pressure dependence of the deformation mechanism through molecular statics simulations.  Recent saddle-point search methods have been employed to investigate the influence of thermal activation on the mechanisms that account for plastic flow of a glass.  In an attempt to investigate larger time and length scales we have also developed mesoscale simulations, which approximate atomistic behavior by utilizing the ‘shear transformation zone’ as the primary carrier of plasticity.  These mesoscale studies are aimed at understanding the link between local deformation events and the shear banding and localization that is observed at a macroscopic scale.  Using these various techniques, we aim to provide information about deformation in a metallic glass across a wide range of time and length scales.

See also the review article:
Mechanical Behavior of Amorphous Alloys in Acta Materialia

a) b)

a) Displacement vectors and energy of a thermally-activated plastic event in a glass. b) A deformation map for a model metallic glass contructed from meso-scale deformation simulations over a range of loads and temperatures. The colored lines represent contours of different steady-state strain rates, where strain rates slower than 10-10 s-1 are considered to be elastic and are marked with an ‘‘x”. Other data points are shaded according to their respective strain rate sensitivity, m, as indicated by the color bar above the map. Further regions marked as Newtonian (lightly shaded) and non-Newtonian are differentiated. Samples which deformed inhomogeneously are marked in a darkly shaded region while the rest of the samples deformed homogeneously.

Published Articles:

Mesoscale modeling of amorphous metals by shear transformation zone dynamics
Homer ER, Schuh CA; ACTA MATERIALIA 57 (9): 2823-2833 MAY 2009 (PDF)

Initiation of a shear band near a stress concentration in metallic glass
Packard CE, Schuh CA; ACTA MATERIALIA 55 (16): 5348-5358 SEP 2007 (PDF)

New regime of homogeneous flow in the deformation map of metallic glasses: elevated temperature nanoindentation experiments and mechanistic modeling
Schuh CA, Lund AC, Nieh TG; ACTA MATERIALIA 52 (20): 5879-5891 DEC 2004 (PDF)

The Mohr-Coulomb criterion from unit shear processes in metallic glass
Lund AC, Schuh CA; INTERMETALLICS 12 (10-11): 1159-1165 OCT-NOV 2004 (PDF)

Yield surface of a simulated metallic glass
Lund AC, Schuh CA; ACTA MATERIALIA 51 (18): 5399-5411 OCT 2003 (PDF)

The transition from localized to homogeneous plasticity during nanoindentation of an amorphous metal
Schuh CA, Argon AS, Nieh TG, Wadsworth J; PHILOSOPHICAL MAGAZINE 83 (22): 2585-2597 AUG 2003 (PDF)

Atomistic basis for the plastic yield criterion of metallic glass
Schuh CA, Lund AC; NATURE MATERIALS 2 (7): 449-452 JUL 2003 (PDF)