Investigation of softening induced indentation size effect in Nanoglass and Metallic glasss

Abstract

In this work, binary Cu60Zr40 nanoglasses (NGs) and melt spun ribbons (MGs) are synthesized by using magnetron sputtering in an inert gas condensation (IGC) system and standard melt-spinning, respectively. The bonded interface experiments through micro-indentation, and nanoindentation experiments at different peak loads are conducted on both glasses. In addition, complementary finite element (FE) simulations are performed using finite strain viscoplastic constitutive theory for amorphous metals. The bonded interface experiments reveal smooth and almost semi-circular shaped shear bands in MG, while the formation of wavy shear bands is observed in NG. Further, the primary shear band densities in the MG is higher than that in NG, while the plastic zone size below the indenter is larger in the latter than the former. Furthermore, nanoindentation experiments show that the hardness in NGs as well as MGs decreases with increase in indentation depth signifying both alloys exhibiting the indentation size effect (ISE). However, the ISE is found to be more pronounced in MGs than NGs. The FE simulations show that the less pronounced ISE in NGs is due to the slower softening primarily because of higher friction coefficient, μ in them.