Investigation of Sputter Deposition and Mechanical IndentationBehavior of Zr-based Multi-Component Amorphous Nano-ScaleThin Films via Molecular Dynamics Simulation

• Main Authors: Chun-Yi Wu, 吳俊毅
• Other Authors: Yun-Che Wang
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/56768935871041112860

碩士 === 國立成功大學 === 土木工程學系碩博士班 === 97 === Molecular-dynamics (MD) models of the Zr-based metallic-glass film (Zr47Cu31Al13Ni9, in atomic percent) were constructed via simulating sputter depositions. The as-deposited films were used as initial structures for subsequent nano-indentation simulations. For the deposition simulations, a many-body, tight-binding potential was adopted for interatomic interactions among the multiple species of atoms. Interactions between the metallic atoms and working gas (Ar+) were modeled with the pair-wise Moliere potential. The deposition simulations revealed an amorphous morphology of the as-deposited films. Indentation simulations with a right-angle conical indenter tip showed a homogeneous flow to form pile-ups on the surface of the metallic glass around the indent. The pileup index calculated from MD is consistent with that obtained from the experiment. Moreover, our MD results show that the pileup index exhibits anomalies, defined as unusual changes in the values of the pileup index, around the glass-transformation temperature (758 K) through in situ indentation simulations. From indentation load-displacement curves at various temperatures, it is found that indentation modulus and hardness obtained from MD simulations are in agreement with experimental findings in terms of their decreasing rates with respect to the temperature. The hardness in experiment is 5.2GPa and in MD simulation is 7GPa. The decreasing rate of hardness is about 2MPa/K. The Young’s modulus in experiment is 80GPa and in MD simulation is 40GPa. The decreasing rate of Young’s modulus is about 22MPa/K. Since the formation and propagation of shear bands in metallic glasses dominate their mechanical properties, we perform three-dimensional atomic-strain calculations, and study the connections between the strain localization and propagation of shear bands under the indenter tip. In addition, higher loading rates decrease hardness, and cause larger disturbed regions under the indent, and enlarge shear-banding patterns.