Cooperative Shear in Bulk Metallic Glass Composites Containing Metastable <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>β</mml:mi></mml:math>-Ti Dendrites
Long Zhang, R. Lakshmi Narayan, Baoan Sun, Tianying Yan, Upadrasta Ramamurty, J. Eckert, Haifeng Zhang
Abstract
We report a novel plastic deformation mechanism of bulk metallic glass composites (BMGCs) containing metastable $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Ti}$ dendrites. Plastic deformation of the BMGCs beyond the ultimate tensile strength is mediated by cooperative shear events, which comprise a shear band in the glassy matrix and a continuous $\ensuremath{\omega}\text{\ensuremath{-}}\mathrm{Ti}$ band with a thickness of $\ensuremath{\sim}10\text{ }\text{ }\mathrm{nm}$ in the $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Ti}$ dendrite. The cooperative shear leads to serrated shear avalanches. The formation of narrow $\ensuremath{\omega}\text{\ensuremath{-}}\mathrm{Ti}$ bands is caused by high local strain rates during the cooperative shear. The cooperative shear mechanism enriches the deformation mechanisms of BMGCs and also deepens the understanding of $\ensuremath{\omega}\text{\ensuremath{-}}\mathrm{Ti}$ formation.