Abstract
Metallic glasses exhibit not only multiple failure modes but also differences in ultimate strength, plastic strain to fracture and asymmetric deviation of failure angles from 45° between tension and compression. The available failure theories cannot fully characterize these phenomena and the underlying physics has not been completely clarified. Here, based on the short-range order structure in metallic glasses, we derive an inherent law that determines when metallic glasses might yield or fracture. A unified failure criterion is constructed which satisfactorily predicts the complex failure behavior observed in metallic glasses. We show that the shear-to-normal strength ratio and the strength-differential factor
, characterizing shearing resistance between atomic layers and shear-caused dilatation, respectively, have dual control over whether metallic glasses yield in a ductile manner or fracture in brittleness.
Acknowledgements
Financial support from the NSFC (Grants Nos. 10725211, 11002144 and 11021262), the National Natural Science Foundation of China-NSAF (Grant No. 10976100), the National Basic Research of China (Grant No. 2009CB724401), and the Key Project of Chinese Academy of Sciences (Nos. KJCX2-YW-M04) is acknowledged.