Investigation of the relationship between primary and secondary shear bands induced by indentation in bulk metallic glasses

This present study is aimed to establish an analytical model for investigating primary shear band (PSB) and secondary shear band (SSB) circles of bulk metallic glasses (BMGs) obtained from Vickers indentations and those reported in the literatures. Using the force balance for an arbitrary PSB annulus, the spacing of a shear band is expressed as a linear function of its inner radius, and the radius ratio of any two adjacent PSB circles is approximately a constant value. The radii of orthogonal SSB circles are root 2 times as large as the radius of its corresponding PSB circle. Good agreement between the shear band circles predicted by the proposed model and the experimental results was obtained for both PSB and SSB. The proposed model can be employed to evaluate the ratio of the deformation zone to the half-diagonal contact length (or the contact radius in spherical and conical indentation) of BMG materials. The microstructures of the Zr53Cu30Ni9Al8 BMG material remained amorphous before and after the appearance of shear bands. The formation of shear bands is mainly dominated by cracking rather than crystallization. (C) 2010 Elsevier Ltd. All rights reserved.