Microstructural characterisation of stir zone containing residual ferrite in friction stir welded 304 austenitic stainless steel

S. H.C. Park, Yutaka Sato, Hiroyuki Kokawa, K. Okamoto, S. Hirano, M. Inagaki

Research output: Contribution to journalArticlepeer-review

78 Citations (Scopus)

Abstract

Friction stir welding was applied to a 2 mm thick 304 austenitic stainless steel plate. The microstructural evolution and hardness distribution in the weld were investigated. The stir zone (SZ) and thermomechanically affected zone (TMAZ) showed dynamically recrystallised and recovered microstructures, respectively, which are typically observed in friction stir welds in aluminium alloys. The hardness of the SZ was higher than that of the base material and the maximum hardness was observed at the TMAZ. The higher hardness at the TMAZ was attributed to high densities of dislocations and subboundaries. Microstructural observations revealed that the ferrite was formed along grain boundaries of the austenite matrix in the advancing side of the SZ. It is suggested that the frictional heat due to stirring resulted in the phase transformation of austenite to ferrite and that upon rapid cooling the ferrite was retained in the SZ.

Original languageEnglish
Pages (from-to)550-556
Number of pages7
JournalScience and Technology of Welding and Joining
Volume10
Issue number5
DOIs
Publication statusPublished - 2005 Sep 1

Keywords

  • 304 austenitic stainless steel plate
  • Ferrite
  • Friction stir welding
  • Hardness distribution
  • Microstructural evolution
  • Phase transformation
  • Stir zone
  • Thermomechanically affected zone

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics

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