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Resistance spot welding of ultra-fine grained steel sheets produced by constrained groove pressing: Optimization and characterization

Khodabakhshi, F ; Sharif University of Technology | 2012

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  1. Type of Document: Article
  2. DOI: 10.1016/j.matchar.2012.04.011
  3. Publisher: 2012
  4. Abstract:
  5. Constrained groove pressing as a severe plastic deformation method is utilized to produce ultra-fine grained low carbon steel sheets. The ultra-fine grained sheets are joined via resistance spot welding process and the characteristics of spot welds are investigated. Resistance spot welding process is optimized for welding of the sheets with different severe deformations and their results are compared with those of as-received samples. The effects of failure mode and expulsion on the performance of ultra-fine grained sheet spot welds have been investigated in the present paper and the welding current and time of resistance spot welding process according to these subjects are optimized. Failure mode and failure load obtained in tensile-shear test, microhardness, X-ray diffraction, transmission electron microscope and scanning electron microscope images have been used to describe the performance of spot welds. The region between interfacial to pullout mode transition and expulsion limit is defined as the optimum welding condition. The results show that optimum welding parameters (welding current and welding time) for ultra-fine grained sheets are shifted to lower values with respect to those for as-received specimens. In ultra-fine grained sheets, one new region is formed named recrystallized zone in addition to fusion zone, heat affected zone and base metal. It is shown that microstructures of different zones in ultra-fine grained sheets are finer than those of as-received sheets
  6. Keywords:
  7. Ultra-fine grain ; Base metals ; Constrained groove pressing ; Failure load ; Fusion zones ; Mode transitions ; Optimum welding conditions ; Resistance spot welding ; Scanning Electron Microscope ; Severe Deformation ; Severe plastic deformations ; Spot weld ; Tensile shear test ; Ultra-fine grained steel ; Ultrafine-grained ; Via resistance ; Welding current ; Welding parameters ; Aluminum sheet ; Characterization ; Electric welding ; Scanning electron microscopy ; Spot welding ; Steel sheet ; Transmission electron microscopy ; X ray diffraction ; Optimization
  8. Source: Materials Characterization ; Volume 69 , 2012 , Pages 71-83 ; 10445803 (ISSN)
  9. URL: http://www.sciencedirect.com/science/article/pii/S1044580312001088