Abstract
The effects of nanosecond laser peening on Zr41Ti14Cu12.5Ni10Be22.5 metallic glass were investigated in this study. The peening treatment produced an extra-deep shock-affected zone compared to crystal metal. As opposed to the conventional shear bands, numerous arc shear bands appeared and aggregated in the vertical direction of the laser beam, forming basic units for accommodating plastic deformation. The arc shear bands exhibited short and discrete features near the surface of the material, then grew longer and fewer at deeper peened layer depths, which was closely related to the laser shock wave attenuation. An energy dissipation model was established based on Hugoniot Elastic Limit and shear band characteristics to represent the formation of an extra-deep shock-affected zone. The results presented here suggest that the bulk modification of metallic glass with a considerable affected depth is feasible. Further, they reveal that nanosecond laser peening is promising as an effective approach to tuning shear bands for improved MGs ductility.
Highlights
Shot peening has been utilized on a variety of materials for surface strengthening in recent studies, and is especially popular for BMGs29
This paper reports an extra-deep shock-affected zone formed via nanosecond laser peening, that is much larger than the one in conventional crystal metal
Irrecoverable plastic deformation occurs if the laser-induced shock pressure is above the dynamic yield strength of the target material
Summary
Irrecoverable plastic deformation occurs if the laser-induced shock pressure is above the dynamic yield strength of the target material. The shock energy attenuates in BMGs owing to the formation of SBs. The shock pressure profile weakens in amplitude and stretches across time corresponding to an increased length and decreased number of SBs at deeper peened layer depths. The hardness in the shock affected region is smaller than that in the matrix region, and many dips or local extremes appear in the profile owing to the combined effect of both the induced residual stress and SBs. The energy dissipation density is an apparent parameter which reflects the ability of materials for accommodating the applied shear strain and plastic deformation during the laser shock peening. The results reveal that nanosecond laser peening is promising as an effective approach to tuning SBs for improved MGs ductility
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