Flow and fracture of bulk metallic glass alloys and their composites

The fracture and plastic deformation mechanisms of a Zr-Ti-Ni-Cu-Be bulk me tallic glass and a composite utilizing a crystalline reinforcement phase ar e reviewed. The relationship between stress state? free volume and shear ba nd formation are discussed. Positron annihilation techniques were used to c onfirm the predicted increase in free volume after plastic straining. Strai n localization and failure were examined for a wide range of stress states. Finally, methods for toughening metallic glasses are considered. Significa nt increases in toughness are demonstrated for a composite bulk metallic gl ass containing a ductile second phase which stabilizes shear band formation and distributes plastic deformation.