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- Influence of the structure and phase composition of the bond interface on aluminium-copper lap welds strengthPublication . Andrade, David; Galvão, Ivan; Verdera, David; Leitao, Carlos; Rodrigues, DulceThe structure and phase composition of the bond interface of aluminium-copper lap welds produced by friction stir welding and tool-assisted friction welding were analysed. Microstructural analysis proved that no through-interface material flow took place in tool-assisted friction welding and that aluminium-copper joining resulted from the formation of a thin and continuous intermetallic layer at the lap interface. For the welds produced by friction stir welding, evidences of through-interface material flow were found, promoting mechanical interlocking of both base materials, at the lap interface, and formation of discontinuous intermetallic layers. Mechanical testing showed that the tool-assisted friction welds, with excellent surface finishing, had low strength, contrary to the friction stir welds, which displayed excellent bond strength. The comparison of the mechanical and microstructural results, for both weld types, pointed to the ineffectiveness of the continuous intermetallic layer in providing high strength bonding.
- Influence of the galvanized coating thickness and process parameters on heat generation and strength of steel spot weldsPublication . Andrade, David; Sabari, S. Sree; Leitao, Carlos; Rodrigues, DulceThe influence of galvanized coating thickness, tool diameter and rotational speed, on the thermal cycles, in spot welding of steels produced by Tool Assisted Friction Welding (TAFW), a Friction Stir Spot Welding (FSSW) related technique, is analysed. To study the influence of the galvanized coating thickness on the thermal cycles, thin steel plates commonly used in steel construction and automotive industry with galvanized coatings of varied thicknesses were welded. Numerical simulation of the welding process was conducted to understand some of the physical phenomena observed experimentally. Numerical and experimental results were compared and discussed. The influence of the above described parameters, as well as of the dwell time, on welds strength was also characterized. The results showed that steel spot welds with very good mechanical strength can be obtained in very short process cycle times. It was also determined that the welds strength was much higher than the minimum strength recommended for resistance spot welds (RSW).