An investigation of contact deformation,fracture, and fatigue behavior in bulk metallic glasses

This article presents the results of a study of the contact-induced deformation, fracture/resistance-curve behavior, and fatigue-crack-growth behavior of two bulk metallic glasses (BMGs), one in the fully amorphous condition and the other containing a dispersion of microscale crystallites. Hertzian contact indentation experiments were performed on both materials under monotonic loading conditions. The contact-induced deformation characteristics observed in the Hertzian experiments are then compared with the stress distribution determined from finite-element analyses. In addition, the cracking patterns associated with resistance-curve behavior in single-edge notched bend (SENB) specimens are incorporated into a fracture-mechanics framework for the estimation of toughening due to microcrack shielding. The predicted steady-state toughness values are shown to be comparable to the measured values obtained from resistance-curve experiments. Subsequently, fatigue-crack-growth rare data obtained at stress ratios of 0.1 and 0.5 are presented and analyzed using a crack-tip opening displacement (CTOD) model. The implications of the results are then discussed.