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Investigation on Formability of Two-layered Stainless Steel-copper Sheets with FLDs

Tavousi Masrour, Sina | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49048 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s):
  7. Abstract:
  8. In this research, two-layered sheets of copper and stainless steel 316 were produced by roll bonding. These sheets provide a combination of properties of copper and stainless steel; including high strength, thermal conductivity and corrosion resistance, as well as low weight and cost-efficient means of production. The effects of thickness reduction, different preheat temperatures and varying heating conditions after rolling on bond strength were studied. In some specimens, an aluminum sheet was used as a middle-layer, which significantly improved the bonding quality. In order to observe the interface of the bonded specimens, optical microscope images of the cross sections were studied. Mechanical properties of the two-layered sheets were determined using tensile and shear punch tests. To study the formability of the Cu/StS sheets, forming limit diagrams of different specimens were determined using experimental data. The results were compared to a three-layered sheet with a mid-layer of aluminum. By heat-treating the bonded specimens, bond-strength can be improved. Specimens heated at 500 and 700 ℃ showed significantly higher bond strength, due to diffusion at interface and improved overall toughness. It is shown that heating for longer durations (up to 1 hour, in this research), results in weaker bonds. Micro-voids and a harmful interlayer will appear by longer heating durations, resulting in reduced bond strength. The FLDs of Cu/StS and Cu/Al/StS showed that the FLD of a multi-layered sheet is between the FLDs of its base sheets. This means that low formability of a sheet can be improved by its bonding to a sheet with higher formability. Using an aluminum mid-layer improved formability because of the stronger bondings between the layers
  9. Keywords:
  10. Forming Limit Diagram (FLD) ; Roll Bonding ; Ductility ; 316 Austenitic Stainless Steel ; Two-layered Copper and Stainless Steel

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