Atomistic simulation of mechanical properties of metallic-glass thin films

  • 吳 俊毅

Student thesis: Doctoral Thesis


Metallic glass is a promising class of materials that provide sufficient hardness and other superior properties for coating purposes In order to know the materials mechanical properties provide a better understanding of structure-property relations and provide more solutions to industry for widely use metallic glass-formers We adopt the molecular dynamics simulation methodology to simulate sputter deposition hence to ‘manufacture’ the (Cu50Zr50)100-xAlx (x = 0 2 4 5 6 8 10 12 atomic percent) metallic-glass thin films on the titanium substrate in the computer The same idea has been used to manufacture Zr-based metallic glasses The sputter deposition simulation includes the interaction between argon ions as the working gas and metallic atoms that are modeled by the tight-binding interatomic potential It is identified that the as-deposited films are amorphous as verified by calculated radial distribution functions of the film calculated being compared with synchrotron experimental data And XRD analysis with a peak at 40 degrees and MSD diffusion mechanism The interface between the titanium substrate and metallic-glass thin film contains penetrated copper zirconia and aluminum atoms that are embedded in the substrate due to sputter kinetic energy In order to characterize the mechanical properties of the metallic-glass film nano-indentation simulations with a right-angle conical indenter tip is adopted and a procedure similar to the experimental Oliver-Pharr method is utilized to extract modulus are 80-120 GPa and hardness 6-8 GPa of the films under normal temperature and pressure by simulation Our calculated quantities are qualitatively in agreement with experimental data In addition the pileup index under different depth-to-thickness ratios are quantitatively obtained to indicate the nature of homogeneous flow at this length scale Then discuss 5%Al under different temperature The decreasing rate of Young’s modulus is about 96 7 MPa/K The decreasing rate of hardness is about 1 1 MPa/K and 9 3 MPa/K Around the glass-transformation temperature 650 K-750 K has some unusual changes and the pileup index also has some unusual issue Furthermore atomic strain calculation reveals deformation localization to identify shear bands Moreover elastic anisotropy is calculated to identify structural anisotropy at the atomic scales and the phenomenon of structural relaxation has been observed which is qualitatively correlated to experimental observables Several calculated indicators show evidence of glass transition of the metallic glasses which are previously un-noticed
Date of Award2014 Sept 1
Original languageEnglish
SupervisorYun-Che Wang (Supervisor)

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