Synchrotron Radiation and Instrumented Indentation Studies of Compressive Plastic Deformation in Zr-Based Bulk Metallic Glasses

Abstract

X-ray diffraction using synchrotron radiation and instrumented indentation experiments has been carried out to trac k free volume changes and local reodering following plastic straining by indentation below the glass transition temperature Tg in the Zr60Ni10Cu20Al10, Zr 65 Ni 10 Cu 15 Al 10 and Zr 65 Ni 10 Cu 7.5 Al 7.5 Pd10 metallic glass forming systems. A quantitative diffraction line profiles modifications are observed during scanning strained and unstrained zones of the same specimen. We have found that the first diffractogram maximum intensity in transmission and the average inter-atomic spacing position are significantly affected in the overlapping shear bands around impressions. The surface uplift of the pile-up around indents has been assessed using a profilometer. It is shown that the inhomogeneous deformation results in an inhomogeneous distribution of free volume concentration. Substantial plastic deformation is determined form hysteresis loops recorded during nanoindentation experiments. While the ratio of the dissipated energy to total indentation work is quite similar for Zr-based metallic glasses, continuous stiffness measurements showed an appreciable difference in the evolution of the elastic modulus and hardness as function of penetration depth.