Toughening a bulk metallic glass through mode II fracture under mode I loading

•Mode II fracture under mode I loading was discovered in a bulk metallic glass.•Mode II fracture was induced by pivoting of the rigid ends of sample around circular arc shear bands.•Cavitation through which solids fractures was totally suppressed.•The pivoting increased energy dissipation and diminished hydrostatic tension ahead of crack tip. High fracture toughness is vital for resisting catastrophic fracture of engineering structural materials which break through cavitation instability. We report a new toughening mechanism which totally suppressed cavitation through pure mode II fracture which was induced by pivoting around circular arc shear bands in a bulk metallic glass under mode I loading. We demonstrated that the mode II crack propagated along the outmost circular arc shear band along Prandtl slip line which is the orientation of maximum shear stress ahead of crack tip. Our theoretical investigation revealed that enhanced critical hydrostatic tension for cavitation which changed the stress field ahead of fatigue crack tip would be the trigger for pivoting which would increase energy dissipation and prevent hydrostatic tension ahead of crack tip from increasing. The present work would assist in guiding microstructure design to produce monolithic and composite materials with enhanced fracture toughness. Materials fracture through cavitation. We developed a bulk metallic glass which undergoes pure shear fracture instead of cavitation with high toughening rate and toughness. The toughening rate is even higher than the slope of KI-COD curve in elastic region. This should be caused by pivoting of the rigid ends of the specimen around circular arc shear bands which is along the direction of Prandtl slip line. Our theoretical investigation revealed that enhanced critical hydrostatic tension for cavitation would be the trigger for pivoting which would increase energy dissipation and prevent hydrostatic tension ahead of crack tip from increasing. [Display omitted]