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Investigation of the Effects of Various Parameters on Microstructure and Mechanical Properties of Nano-Composite Al-Al2O3 and Al-Sic Produced by Accumulative Roll Bonding

Rezayat, Mohammad | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41429 (07)
  4. University: Sharif University of Technology
  5. Department: Material Science and Engineering
  6. Advisor(s): Akbarzadeh Changiz, Abbas
  7. Abstract:
  8. Accumulative roll bonding has been used as novel method to produce the composite with ultra fine grain microstructure. This method has two steps, impose the particles as reinforcement between the layers by roll bonding process and then distribute the particles in matrix and generat an ultra fine grain microstructure during the ARB passes. In the present work, ARB process was performed to produce the Al/SiC and Al/Al2O3 nano-composites with various particles size and different volume fraction of reinforcement. Microscopic observations such as OM, SEM and TEM and XRD analyses were used to investigate the microstructure of produced composites and the distribution of the particles in matrix and then the mechanical properties of the composites were inspected by tensile test and Vickers micro hardness. The effects of processing parameters on bond strength were studied to specify the best condition in roll bonding step. Furthermore an analytical model was generated to predict the threshold reduction in presence of powder layer at interface in roll bonding. It was found that ARB can be useful to product the metal matrix composite that reinforced by nano particles. Indeed results show that presence of particles in matrix can enhance the ultimate tensile strength up to 1.5 times higher than of unreinforced accumulative roll bonded sample, because of simultaneity activity of strengthening mechanisms in nano-composites and strengthening mechanisms during the ARB. Also investigation of fracture surfaces illustrated the suitable bond strength at interface of particle-matrix. It was indicated that Al/SiC composite due to low expansion coefficient of SiC particles, has better mechanical properties rather than Al/Al2O3 composite. The interaction between the possibility of formation of defects and improvement of the mechanical properties justifies formation of a maximum point in the tensile strength versus renforcement content. It was also observed that increase in ARB temperature caused to improve all of the mechanical properties especially in Al/SiC composite. XRD analyses revealed that by increasing the ARB temperature, cell size reduced and, moreover, shear texture developed in microstructure. To improve the ductility of fabricated composites, annealing process was carried out and by 37% decrease in UTS, fracture strain increased up to 100%
  9. Keywords:
  10. Roll Bonding ; Accumulative Roll Bonding (ARB) ; Al-5vol%Al2O3 Nanocomposite (Al2o3) ; Aluminum-Silicon Alloy ; Mechanical Properties

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