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Processing of Nanostructured Composite from Al1050 and Al2024 Via Aaccumulative Roll Bonding (ARB) and Study of Heattreatment Effects on its Microstructure and Mechanical Properties

Sadeghi, Aida | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42555 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Asgari, Sirous
  7. Abstract:
  8. In this study nanostructured composite from Al1050 and Al2024 were manufactured via accumulative roll bonding (ARB). Process was conducted in two different ways. In one approach the Al2024 sheets were annealed and in the other they were solution treated (ST). The sheets were degreased by acetone and wire-brushed, and then one Al2024 was placed between two sheets of Al1050, so three pieces of sheets were stacked to be 3 mm in thickness. The stacked sheets were rollbonded to produce the primary composite sandwich with thickness of 1 mm. Then, this sandwich was cut in the half and the two halves were degreased and wire-brushed and stacked to be 2 mm in thickness. Roll-bonding was conducted again to produce sheets with 1 mm in thickness. This procedure was repeated up to 8 cycles corresponding to 6.87 of ARB equivalent strain. Completing the process, produced sheets were maintained at -15ºC to avoid precipitation. The microstructure investigation was carried out by SEM and mechanical properties were investigated through tensile tests and Vickers microhardness measurements. SEM results manifested that in composites that Al2024 was annealed, the Al2024 layers have fragmented and distributed homogeneously through thickness. While, in samples with ST Al2024, these layers not only have remained massive but also have inhomogeneous distribution. Tensile test results showed that in composites with ST Al2024 ultimate tensile strength (UTS) augments with the increase in the number of cycles but in composites with annealed Al2024 UTS dwindles with the increase in the number of cycles. According to microhardness measurement, microhardness boosts with the increase in the strain, but have tangible increase at primary cycles. After ARB, some samples were annealed at three temperatures; room, 150ºC and 190ºC. Microstructure and tensile properties were surveyed. SEM micrographs depicted that volume fraction of precipitates is lower in composites with ST Al2024. The results also portrayed that Cu diffuses into Al1050 in distances about one hundredth of micron. UTS-Aging time diagrams represent a plateau in diagrams after 2 hours aging which is a representative of stable strength
  9. Keywords:
  10. Composite ; Aging ; Accumulative Roll Bonding (ARB) ; Aluminum Alloy 1100 ; Aluminum Alloy 2024 ; Solution Treatment

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