Enhancing ductility in bulk metallic glasses by straining during cooling

Most of the known bulk metallic glasses lack sufficient ductility or toughness when fabricated under conditions resulting in bulk glass formation. To address this major shortcoming, processing techniques to improve ductility that mechanically affect the glass have been developed, however it remains unclear for which metallic glass formers they work and by how much. Instead of manipulating the glass state, we show here that an applied strain rate can excite the liquid, and simultaneous cooling results in freezing of the excited liquid into a glass with a higher fictive temperature. Microscopically, straining causes the structure to dilate, hence “pulls” the structure energetically up the potential energy landscape. Upon further cooling, the resulting excited liquid freezes into an excited glass that exhibits enhanced ductility. We use Zr44Ti11Cu10Ni10Be25 as an example alloy to pull bulk metallic glasses through this excited liquid cooling method, which can lead to tripling of the bending ductility. Bulk metallic glasses typically display limited ductility. Here, straining a bulk metallic glass during cooling from the supercooled region is shown to enhance bending ductility, attributed to the structure being pulled up the potential energy landscape.