Characterization of inelastic deformation in metallic glass using instrumented indentation

The plastic flow behavior of bulk metallic glasses (BMGs), which is difficult to determine by uniaxial tensile tests, was characterized by instrumented spherical indentation tests. Apparent flow stress–indentation strain curves were obtained by analyzing the contact depth and induced pressure based on an established analysis. However, a work-hardening index of 0.18 (or rapid increase in the apparent flow stress from 1170 to 2020 MPa with indentation strain) was measured, significantly different from typical BMG flow properties. We suggest a new parameter, defined as the ratio of intercept depth to peak depth, for predicting the plastic constraint factor, and recalculate the flow stresses using this parameter. The recalculated flow curve of the Zr-based BMG yielded more reasonable work-hardening index of 0.048, and the validity of this modification was verified empirically.