Abstract
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.
Highlights
Most of the known bulk metallic glasses lack sufficient ductility or toughness when fabricated under conditions resulting in bulk glass formation
The extent to which straining enhances the fictive temperature depends on the difference between the time scales set by the strain rate, which increases the potential energy, and by structural relaxation, which decreases the potential energy
The sample is air cooled whilst simultaneously applying a load of 1–100 N which rapidly strains the sample, and by varying the load, the strain rate can be manipulated (Fig. 1)
Summary
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, 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. A summary of previous results can be found in the Supplementary Table 1 Among these methods addressing the glass are some that offer practical methods to enhance ductility in BMG forming alloys[25]. An increase in fictive temperature is reflected in an increase in ductility which we measure in bending
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