Friction stir spot welding of Mg-alloy AZ91 is investigated. The temperature cycles within the stir zone and in the TMAZ region are examined using thermocouples, which are located within the tool itself and also by locating thermocouples in drilled holes at specific locations relative to the bottom of the tool shoulder and the periphery of the rotating pin. The measured temperatures in the stir zone range from 437°C to 460°C (0.98Ts, where Ts is the solidus temperature in degrees Kelvin) in AZ91 spot welds produced using plunge rates from 2.5 and 25 mm/s.The thermal cycle within the stir zone formed during AZ91 spot welding could not be measured by locating thermocouples within the workpiece in drilled holes adjacent to the periphery of the rotating pin. It is suggested that the drilled holes containing the thermocouples are displaced both laterally and downwards as a result of the helical vertical rotational flow, which is created within the stir zone during the dwell period in spot welding.The stir zone microstructures in AZ91 spot welds typically comprise fine equiaxed α-Mg grains. However, spot welds produced with or without the introduction of a thermal insulating layer between the bottom of the AZ91 test section and the upper surface of the steel anvil show evidence of liquid penetration, eutectic segregation and cracking in the locations close to the stir zone extremities. Cracking is also observed in the TMAZ region of spot welds produced with a thermal insulating layer between the bottom of the AZ91 sections and the upper surface of the steel anvil.


    Access

    Check access

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Eutectic Segregation and Cracking in AZ91 Friction Stir Spot Welds


    Additional title:

    Sae Technical Papers


    Contributors:
    Gerlich, A. (author) / Yamamoto, M. (author) / Su, P. (author) / North, T.H. (author)

    Conference:

    SAE World Congress & Exhibition ; 2007



    Publication date :

    2007-04-16




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




    Eutectic Segregation and Cracking in AZ91 Friction Stir Spot Welds

    Yamamoto, M. / Su, P. / Gerlich, A. et al. | British Library Conference Proceedings | 2007


    Eutectic segregation and cracking in AZ91 friction stir spot welds (FSSW)

    Yamamoto,M. / Su,P. / Gerlich,A. et al. | Automotive engineering | 2007


    Energy Generation and Stir Zone Dimensions in Friction Stir Spot Welds

    Gerlich, A. / Bendzsak, G. J. / Su, P. et al. | SAE Technical Papers | 2006


    Energy generation and stir zone dimensions in friction stir spot welds

    Su,P. / Gerlich,A. / North,T.H. et al. | Automotive engineering | 2006


    Factors Affecting the Properties of Swept Friction Stir Spot Welds

    Tweedy, B. M. / Widener, C. A. / Burford, D. A. et al. | SAE Technical Papers | 2008