Understanding the tensile fracture of deeply-notched metallic glasses

[摘要] Deeply-notched metallic glasses can achieve significantly enhanced nominal tensile strain and strength under tension, and show the characteristics of dimples and cup-and-cone morphology on the fractographs. It has been expected that this deep-notch enhancement effect is resulted from the suppressed shear banding. In this study, we provided another interpretation for this effect through stress/strain field analyses based on the ellipse criterion. The results revealed the existence of relatively low but highly dispersed stress/strain instead of highly enhanced and localized stress/strain in deeply-notched metallic glasses, and therefore the actual stress is much lower than the nominal value. Owing to the positive third principal stress condition, the failure angle predicted by the ellipse criterion shifted from 45 degrees at the edge of the notch to 90 degrees at the center of the specimen, which was consistent with the cup-and-cone fracture morphology. These findings clarify the very high nominal stress/strain and special fracture process in deeply-notched metallic glasses. Our work provides a useful method to predict the shear-to-tensile failure mode transition of metallic glasses under complex loading conditions. (C) 2020 Published by Elsevier Ltd.

[发布日期] 2020-12-15

[关键词] Metallic glasses;Deep notch;Shear band;Ellipse criterion;Fracture