caa a22 4500 463226194 CHVBK 20180405153227.0 cr unu---uuuuu 170326e20070901xx s 000 0 eng 10.1007/s10853-007-1662-2 doi (NATIONALLICENCE)springer-10.1007/s10853-007-1662-2 Cracking in the stir zones of Mg-alloy friction stir spot welds [Elektronische Daten] [Motomichi Yamamoto, Adrian Gerlich, Thomas North, Kenji Shinozaki] Liquid penetration induced (LPI) cracking is investigated during friction stir spot weld of AZ91, AZ31 and AM60 magnesium alloys. A combination of stir zone temperature measurement and detailed metallography has revealed differences in the cracking tendencies of different magnesium alloys when the dwell time during spot welding is varied. LPI cracking in AZ91 spot welds involves the following sequence of events: the formation of $$\alpha-\hbox{Mg}\,+\,\hbox{Mg}_{17}\hbox{Al}_{12}$$ eutectic films in the thermo-mechanically affected zone (TMAZ) region immediately adjacent to the stir zone extremity, engulfment of melted eutectic films as the stir zone width increases during the dwell period, penetration of α−Mg grain boundaries and crack propagation when torque is applied by the rotating tool. Cracking occurs early in the dwell period during AZ91 spot welding and almost the entire stir zone is removed when the rotating tool is withdrawn. However, crack-free AZ31 and AM60 spot welds are produced when a dwell time of 4s is used since the stir zone temperatures are much higher than the α-Mg + Mg17Al12 eutectic temperature (437°C) and melted eutectic films dissolve rapidly following their engulfment by the growing stir zone. In contrast, the temperature during the dwell period in AZ91 spot welding is close to 437°C and melted eutectic films are not completely dissolved so that spot welds produced using a dwell time of 4s exhibit LPI cracking. Springer Science+Business Media, LLC, 2007 Yamamoto Motomichi Department of Mechanical System Engineering, Graduate School of Engineering, Hiroshima University, 1-4-1, Kagamiyama, 739-8527, Higashi-Hiroshima, Hiroshima, Japan aut Gerlich Adrian Department of Materials Science and Engineering, University of Toronto, 184 College St., Rm.140, M5S3E4, Toronto, Canada aut North Thomas Department of Materials Science and Engineering, University of Toronto, 184 College St., Rm.140, M5S3E4, Toronto, Canada aut Shinozaki Kenji Department of Mechanical System Engineering, Graduate School of Engineering, Hiroshima University, 1-4-1, Kagamiyama, 739-8527, Higashi-Hiroshima, Hiroshima, Japan aut Journal of Materials Science Kluwer Academic Publishers-Plenum Publishers; http://www.springer-ny.com 42/18(2007-09-01), 7657-7666 0022-2461 42:18<7657 2007 42 10853 https://doi.org/10.1007/s10853-007-1662-2 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10853-007-1662-2 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Yamamoto Motomichi Department of Mechanical System Engineering, Graduate School of Engineering, Hiroshima University, 1-4-1, Kagamiyama, 739-8527, Higashi-Hiroshima, Hiroshima, Japan aut NATIONALLICENCE 700 1- Gerlich Adrian Department of Materials Science and Engineering, University of Toronto, 184 College St., Rm.140, M5S3E4, Toronto, Canada aut NATIONALLICENCE 700 1- North Thomas Department of Materials Science and Engineering, University of Toronto, 184 College St., Rm.140, M5S3E4, Toronto, Canada aut NATIONALLICENCE 700 1- Shinozaki Kenji Department of Mechanical System Engineering, Graduate School of Engineering, Hiroshima University, 1-4-1, Kagamiyama, 739-8527, Higashi-Hiroshima, Hiroshima, Japan aut NATIONALLICENCE 773 0- Journal of Materials Science Kluwer Academic Publishers-Plenum Publishers; http://www.springer-ny.com 42/18(2007-09-01), 7657-7666 0022-2461 42:18<7657 2007 42 10853 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer