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Resistance Spot Welding of Galvanized and Low Carbon Steel Sheet to 5XXX Aluminum Alloy

Arghavani, Mohammad Reza | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47340 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kokabi, Amir Hossein; Movahhedi, Mojtaba
  7. Abstract:
  8. Joining between aluminum alloys and steels by resistance spot welding accompanies critical technological and metallurgical difficulties. The main problem is formation of brittle intermetallic compounds (IMC) at the welding interface which results in poor mechanical properties. There are some researches based on the microstructure and mechanical properties of resistace spot welding of aluminum to steel and each of them has tried to enhance the joint properties. Using Zn interlayer is an approach to improve Al to steel resistance spot welding properties. Up to now there is few information on the influence of Zn as an interlayer between steel and aluminum on the Al/Steel dissimilar welding process. The purpose of the present work is comparison and evaluation of microstructure and mechanical properties of aluminum to galvanized and low carbon steel resistance spot welds. The influences of welding parameters have been investigated. A field emission scanning electron microscope (FE-SEM) has been used in order to study the microstructural issues and fracture surface features. The results showed that process caused the aluminum to be melted and formed the weld nugget while steel was just affected by the produced heat with no indication of melting. The produced heat resulted in the formation of IMC layer in the interfacial of both joints. Presence of Zn coat on galvanized steel led to reduction of IMCs thickness and the stresses. Thus resistance spot welding of aluminum to galvanized steel has higher potential for reaching to better properties. The results of the shear-tensile tests showed that Al to galvanized steel fracture force increased up to 586% by increasing heat input. Fracture surface studies also showed cracks propagated predomantly from layers. Further surfaces included brittle features. There were also some regions in which cracks changed their paths towards the aluminum with brittle features
  9. Keywords:
  10. Resistance Spot Welding ; Intermetallic Compounds ; Dissimilar Joint ; Aluminum Alloy Series 5xxx ; Low Carbon Steel ; Aluminum To Steel Welding

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