Microstructural analysis of the stir zone of Al alloy produced by friction stir spot welding

Mitsuo Fujimoto, Shinji Koga, Natsumi Abe, Sato S. Yutaka, Hiroyuki Kokawa

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


The present, study applied Friction Spot. Joining (FSJ), which was recently developed as a lap joining technique of Al alloys, to two sheets of Al alloy 6061, 1mm in thickness, and then examined the microstructural feature in the weld. The weld had the nugget-shaped stir zone around the exit hole of the probe, and the stir zone exhibited the equiaxed grain structure having finer grain size than that, of the base material. The crystallographic texture analysis using electron backscattered diffraction method suggested that the material movement occurred along the rotating direction of the welding tool in the wide region including the stir zone. In the periphery of the nugget-shaped stir zone, which was characterized as region having the finer grain size than, that of the stir zone interior, any inclusions and precipitates were not found in the SEM scale. The weld was softened around the weld center. The softening could be explained by dissolution and/or growth of the strengthening precipitates due to thermal cycle of FSJ.

Original languageEnglish
Pages (from-to)553-559
Number of pages7
JournalYosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society
Issue number4
Publication statusPublished - 2007


  • Aluminum alloy
  • Friction stir spot welding
  • Grain size
  • Hardness
  • Plastic flow
  • Stir zone

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Surfaces, Coatings and Films
  • Metals and Alloys


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