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Physical Modeling of Metal Matrix Composite Sheets With Second Phase Manufactured by Accumulative Roll Bonding (ARB) of Al-Ni Laminations

Rezaei Anvar, Behrouz | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40965 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Akbarzadeh, Abbas
  7. Abstract:
  8. Metallic multilayer composites provide remarkable mechanical, electrical and magnetic properties. These kinds of composites have been recently processed by severe plastic deformation (SPD) methods. Accumulative roll bonding (ARB) is one of the SPD processes in which accumulation of strain by repeating cycles, leads to the ultra fine grained materials. The goal of this research is manufacturing of Al/Ni composite sheets by ARB process considering the effects of thickness and number of initial sheets on their mechanical properties and microstructures. The initial composites were produced by commercially pure Al and Ni as the matrix and the reinforcement, respectively. Thickness of the Al layers was 0.5 mm and the thickness of Ni layers were selected as 0.60, 0.46 and 0.40 mm in 3, 5 and 7 initial layers composites, respectively, providing constant volume fraction of reinforcements. For production of initial layered composites, the stacked laminations of Al and Ni sheets were rolled down to 0.5 mm (by 3, 79 and 84% reduction in initial 3, 5 and 7 layers composites, respectively) at ambient temperature. The 3, 5 and 7 layers sandwiches, then, ARBed up to 7, 7 and 8 cycles, respectively. Interfacial strength of the Al and Ni layers were investigated by peeling and bending tests. Structural and microstructural evaluations of initial layers and ARBed composites were carried out by optical and SEM microscopes. Interfacial zones of different composites are studied by line scan analysis of energy dispersive spectroscopy. The tensile properties of composites are measured at 0, 45 and 90 degrees with respect to the rolling direction. Microhardness tests were carried out on Al and Ni layers of composites. It is observed that by increasing the ARB cycle numbers, in addition to homogenous distribution of the Ni phase, the morphology of Ni layers gradually changes from layer to particle type. And, by increasing ARB cycles, grain size of the Ni layers decrease. Remarkable diffusion of Al and Ni atoms under processing condition, indicates formation of non-equilibrium solid solution. The results indicate that yield strengths of composite sheets increase by ARB cycles. Total elongation of the composites after the initial decrease is also increased by ARB cycles. Due to variation of morphological anisotropy of reinforcing phase along different directions, the final sheet exhibits lower strength along the RD comparing to other directions. Increase of the number of initial layers results in better properties of composites, because of larger initial strain in addition to better and more uniform dispersion of the reinforcing phase.

  9. Keywords:
  10. Microstructure ; Mechanical Properties ; Anisotropy ; Ultra Fine Grain Structure ; Accumulative Roll Bonding (ARB) ; Multilayered Composite ; Laminated Sheets

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