An investigation of fatigue in an Fe-based metallic glass by nanoindentation

Abstract

An Iron-based bulk metallic glass was studied using nanoindentation to examine the effects of fatigue on the onset of plasticity. Experiments were performed on samples in an as received and 0.8Tg 12-hour annealed condition. The nanoindentation testing procedure focused on investigating fatigue of these samples through cyclic loading as well as investigating the maximum shear stress induced through varied loading in the as-received sample. With respect to the maximum induced shear stress, no clear correlation between induced stress and the onset of plasticity in this material was observed. The results of fatigue in the as-received sample demonstrate material strengthening upon repeated loading, while the effect is absent in the annealed sample. The results are discussed in relation to material structure and free volume, and analysis suggests that structural relaxation during annealing serves to inhibit material strengthening by fatigue in metallic glasses, while cycling in the as-received sample likely strengthens due to a local effect.