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Investigation of Structure, Microstructure and Mechanical Properties of Al/AZ31 Composite Produced by ARB

Sabeti, Ali | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39133 (07)
  4. University: Sharif University of Technology
  5. Department: Materials science and Engineering
  6. Advisor(s): Akbarzadeh Changiz, Abbas
  7. Abstract:
  8. Metallic multilayer composites provide remarkable mechanical, electrical and magnetic properties. These kinds of composites are recently processed by severe plastic deformation methods. Accumulative roll bonding (ARB) is one of the SPD processes in which accumulation of strain by repeating cycles, leads to the ultra fine grains structures. The goal of this research is manufacturing of Al/AZ31 composite and investigating the relation between the rolling process parameters and the mechanical and physical properties of the final sheet. The initial composite was carried out by cladding of 1mm thick AZ31 sheet in between two commercially pure aluminum sheets with the same thickness (57% reduction at 375oC). The composite sheet was then processed through 7 cycles of ARB. The structural and microstructural evolutions were analytically studied by means of microscopic images. EDX and Line scan analysis of SEM were conducted to study the interface of Al and AZ31 layers. Tensile and microhardness tests were also utilized to evaluate mechanical properties. It is observed that by increasing the ARB cycle numbers, in addition to homogenous distribution of AZ31 phase, the morphology of AZ31 layers gradually change from layer to particle shape. Furthermore, remarkable diffusion of Al and Mg atoms were observed under the processing conditions, which results in formation of Al3Mg2 and Al12Mg17 intermetallic phases at Al/AZ31 interface. The results indicate that yield strength of the composite sheets increase through ARB cycles. It is unexpectedly observed that the gradual decrease in elongation is changed to an increase during the last two ARB cycles which can be attributed to the change in AZ31 layer shapes. Due to the variation in morphological anisotropy of reinforcing phase along different directions, The final sheet exhibits lower strength along RD comparing to other directions
  9. Keywords:
  10. Composite ; Anisotropy ; Interfaces ; Accumulative Roll Bonding (ARB) ; Ultra-Fine Grained Aluminum Sheet ; Microstructural Changes

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