Structural aspects of elasto-plastic deformation of a Zr-based bulk metallic glass under uniaxial compression

The structural rearrangements occurring during compressive deformation of a plastically deformable Zr52.5Ti5Cu18Ni14.5Al10 bulk metallic glass have been investigated in situ using high energy synchrotron X-rays. It was found that in the elastic regime, the atomic distances at both short and medium range order vary linearly with macroscopic stress where the atomic bonds in short range order appear significantly stiffer than medium range order. Upon elastic loading, a small fraction of bonds in the first shell is broken in the loading direction whereas some new bonds are formed in the transverse direction. Atomic strain-stress correlation at medium range order deviates from linearity at the onset of plastic deformation which was correlated to the activation of irreversible STZs. This was confirmed by quantifying the amount of atomic shear strain value during loading. The length scale of 12.5 Å indicated the largest shear strain and is thought to be the most effective length scale in the formation of STZs. The typical fracture angle of this BMG was explained by the orientation of maximum atomic shear strain at the onset of major shear band formation.