Study of mechanical deformation in bulk metallic glass through instrumented indentation

Instrumented sharp indentation experiments at the nano- and micro-length sc ales were carried out in an attempt to quantify the deformation characteris tics of Vitreloy 1 (TM) bulk metallic glass. The experiments were accompani ed by detailed three-dimensional finite element simulations of instrumented indentation to formulate an overall constitutive response. By matching the experimentally observed continuous indentation results with the finite ele ment predictions, a general Mohr-Coulomb type constitutive description was extracted to capture the dependence of multiaxial deformation on both shear stresses and normal stresses. This constitutive response is able to provid e accurate predictions of the evolution of shear bands seen in uniaxial com pression tests. Constrained deformation of the material around the indenter results in incomplete circular patterns of shear bands whose location, sha pe and size are also captured well by the numerical simulations. The analys is is also able to predict the extent of material pile-up observed around t he indenter. The surface deformation features are also consistent with mech anisms such as localized shear flow, serrated yielding and adiabatic heatin g, which are observed during macroscopic mechanical tests. (C) 2001 Acta Ma terialia Inc. Published by Elsevier Science Ltd. All rights reserved.