Indenter Size Effect In High-Pressure Torsion Deformed Pd-Based Metallic Glass

We performed nanoindentation measurements on as-cast and high-pressure-torsion deformed Pd-based metallic glass samples with spherical indenters of radius 1, 5 and 8 mu m. The different serrated behaviors observed during nanoindentation were connected to the microstructural changes evidenced indirectly by differential scanning calorimetry and directly by electron microscopy. On the deformed sample, the discontinuities remained with the 1-mu m indenter, decreased in intensity with the 5-mu m indenter and disappeared with the 8-mu m indenter. The different plastic zone sizes below the indenters can explain this effect since a larger plastic zone offers more possibility for interactions with pre-existing shear bands.