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Investigation of Heat Treatment on Microstructure of Bulk Metallic Glass By Molecular Dynamics

Naseri Karimi, Vahid | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51982 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ashouri, Hossein; Tavakoli, Rouhulla
  7. Abstract:
  8. Metallic glasses have been applied in industry owing to their attractive mechanical, physical, and chemical properties. such as high electrical resistivity, soft-type superconductivity, good magnetic softness, high strength and large elastic strain. These unusual properties make the amorphous alloys potentially useful for various applications, which originate from the intrinsic random atomic configuration. but their plasticity is low and this disadvantage limites their applicable range as a engineering material. In this study we try to improve plasticity of metallic glasses by structural rejuvenation. Structural rejuvenation in metallic glasses by a thermal process (i.e. through recovery annealing) was investigated theoretically by molecular daynamics simulations for Cu64Zr36 BMG as a Cu-Zr BMG with low plasticity. An increase in the potential energy, a decrease in the density (increasing volume or creation of free volumes), and a change in the local structure as well as mechanical softening were observed after thermal rejuvenation. The glassy structure transforms into a more disordered state with the decomposition of icosahedral short-range order within a temperature range above glasstransition temperature. Therefore, a new glassy structure (rejuvenation) depending on the subsequent quenching rate is generated. We investigated the influence of the thermal treatment parameres on the structural rejuvenation . increasing annealing temperature, cooling rate or annealing time in an aproperiate temperature range, improving plasticity , decreasing elastic modulus are observed.we also investigated Cu-Zr BMG formation was studied
  9. Keywords:
  10. Molecular Dynamics ; Thermal Rejuvenation ; Structural Relaxation ; Voronoi Analysis ; Uniaxial Compression Test ; Mechanical Properties ; Bulk Metallic Glass

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