A study of the relationship between semi-circular shear bands and pop-ins induced by indentation in bulk metallic glasses

In the present study, shear band circles obtained from Vickers indentations (microindentations) on bulk metallic glasses (BMGs) are used to establish the analytical model. Observations of the shear band circle morphologies indicate that the radius ratio of any two adjacent shear band circles is approximately a constant value (C). The modified expanding cavity model developed for the mechanics of shear band is then used to establish the relationship for the pop-ins formed during the loading process of nanoindentations and the shear bands. It was confirmed that the depths of pop-ins are a geometric series with a common ratio of C. The experimental results also indicate that the depth ratio of any two adjacent pop-ins is approximately equal to the radius ratio of two adjacent shear band circles. The ratio of the deformation zone to the contact radius induced by an indentation is a constant, which depends on the constraint factor of the material. The ratios predicted using the present model are consistent with experimental results. After indentation, the shear bands form terraces of various heights. The microstructure and the cause of these terraces are discussed.