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Friction Stir Soldering of Copper Coated Graphite-Copper Joints by Sn-Pb Solder

Ebrahimian, Ali | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48282 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kokabi, Amir Hossein
  7. Abstract:
  8. Friction stir soldering (FSS) or brazing (FSB) as an emerging joining process, was first developed to resolve some shortcomings in FSLW and FSSLW such as excessive IMC layer thickness and confined bond area. Although it has advantages over conventional furnace soldering and/or brazing, including localized heating, less detrimental thermal effects on the substrates and capability to reduce the amount of voids at the joint interface. The aim of this study is to investigate the effects of rotational speed, traverse speed and plunge depth of the pinless tool on the shear strength and electrical resistivity of the copper-coated graphite-copper FSSed joints with the aid of Sn-37Pb solder alloy. At the plunge depth of 0.1 mm, the rotational and traverse speeds were applied in the range of 300-800 rpm and 20-30 mm/min, respectively. Thermal history of the interface below rotating tool was recorded during FSS. Interface microstructural observations via optical and scanning electron microscopy. Compression-shear and four-point test results showed that at constant traverse speed, the shear strength and resistivity of the joint increased and then decreased by rotational speed. This behaviour have been attributed to the domination of the excessive intermetallic compounds layer and the voids formation at high and low rotational speed regimes, respectively as the two strength and conductivity reducing agents. Moreover, application of higher traverse speed at low rotational speeds led to the decrement of the strength and resistivity of the joint and conversely at high rotational speed improved them. Reduction of the joint gap and replacement of the filler-IMC layer by Cu3Sn layer below the tool, resulted by increasing the plunge depth of the tool shoulder from 0.1 to 0.2 mm at the optimised values of the other variables, gave rise to the decrease in the joint strength and resistivity
  9. Keywords:
  10. Specific Electrical Resistivity ; Intermetallic Compounds ; Friction-Stir Soldering Brazing ; Graphite-Metal Joint ; Compression-Shear Strength

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