Guiding and Deflecting Cracks in Bulk Metallic Glasses to Increase Damage Tolerance

Abstract

Pre‐existing shear bands (PESBs) are introduced at stress concentration of bulk metallic glasses. Such PESBs channel and guide cracks to deflect beyond plastic zone in which stress is concentrated while cavitation is inhibited during crack propagation. As a result, the fracture resistance of bulk metallic glasses is improved significantly.

Improvement of dynamic notch toughness for the Zr 56 Co 28 Al 16 bulk metallic glass by local pre-deformation

“…In comparison, upon dynamic loadings, the variation of the notch toughness with the pre-compressive force exhibits a similar tendency, and the value of the notch toughness under dynamic loadings is apparently larger than that under quasistatic cases. The present results demonstrate that the pre-compression can effectively enhance the fracture resistance of ZC BMGs, mainly due to the fact that the pre-existing shear bands can guide and deflect cracks under quasi-static and dynamic conditions [26]. Fig.…”

“…Fig. 3(d) reveals the comparison between quasi-static [26] and dynamic notch toughness of as-cast and pre-compressed ZC BMGs with different pre-compressive loads. It can be clearly seen that upon quasistatic loadings, the notch toughness of as-cast specimens is increased with the pre-compressive force [26].…”

“…3(d) reveals the comparison between quasi-static [26] and dynamic notch toughness of as-cast and pre-compressed ZC BMGs with different pre-compressive loads. It can be clearly seen that upon quasistatic loadings, the notch toughness of as-cast specimens is increased with the pre-compressive force [26]. In comparison, upon dynamic loadings, the variation of the notch toughness with the pre-compressive force exhibits a similar tendency, and the value of the notch toughness under dynamic loadings is apparently larger than that under quasistatic cases.…”

“…Pre-deformation process was also utilized to improve the fracture toughness of BMGs [10,26,27]. In order to promote numerous shear bands along the main crack, crack bifurcation, and a tortuous crack path, cold rolling is used to improve the mode I fracture toughness of the Zr-based BMG [10].…”

“…In order to promote numerous shear bands along the main crack, crack bifurcation, and a tortuous crack path, cold rolling is used to improve the mode I fracture toughness of the Zr-based BMG [10]. Indeed, pre-deformation by the compression can improve the notch toughness of both brittle and tough BMGs under quasi-static conditions, Yi et al [26] fabricated pre-existing shear bands ahead of the notch to provide internal weak interface in a bulk material that guide and deflect the evolving cracks, thereby increasing the crack resistance. Furthermore, the controlled stress wave loading experiments induced sub-critical levels of damage in a notched tough Zr-based BMG show several attempts of the blunting at the moment of crack initiation.…”