Effect of post-weld heat treatment on the mechanical behavior and dislocation density of friction stir welded Al6061

Amir Hossein Baghdadi, Armin Rajabi, Nor Fazilah Mohamad Selamat, Zainuddin Sajuri, Mohd. Zaidi Omar

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Al6061 is a heat-treatable aluminum alloy and an extremely versatile material used in settings where medium to high strength is required. To produce good joints using this alloy, a particular solid-state welding process called friction stir welding (FSW) is preferable instead of the conventional welding methods. In this study, the effects of T6 post-weld heat treatment (PWHT) on the mechanical properties, dislocation density, and microstructure of a friction stir welded (FSWed) Al6061 aluminum alloy were investigated. Results indicated that FSW had degraded the mechanical properties of Al6061. The welding efficiency decreased to 65% compared with the tensile strength of the base metal. After FSW, the samples demonstrated a serrated flow behavior known as the Portevin–Le Chatelier (PLC) effect. This effect was attributed to the nonuniform distribution of hard Mg 2 Si particles, coarsening and/or solutionizing of the strengthening elements in the stir and thermomechanically affected zones, and an over-aging effect in the heat-affected zone of the FSWed sample. However, the T6-PWHT performed on the FSWed sample diminished the PLC effect and concurrently improved the mechanical properties back to its original state. The PWHT also promoted precipitation hardening through a better distribution of Mg 2 Si particles that prevented grain growth and increased the dislocation density due to the applied strain, which subsequently improved the mechanical properties of the FSWed Al6061 alloy.

Original languageEnglish
Pages (from-to)728-734
Number of pages7
JournalMaterials Science and Engineering A
Volume754
DOIs
Publication statusPublished - 29 Apr 2019

Fingerprint

Friction stir welding
Welds
heat treatment
friction
friction stir welding
Heat treatment
Friction
Mechanical properties
Welding
welding
mechanical properties
Aluminum alloys
aluminum alloys
Age hardening
Coarsening
Heat affected zone
Grain growth
precipitation hardening
heat affected zone
high strength

Keywords

  • Al6061
  • Dislocation density
  • FSW
  • PLC
  • Precipitation hardening
  • XRD

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

Effect of post-weld heat treatment on the mechanical behavior and dislocation density of friction stir welded Al6061. / Baghdadi, Amir Hossein; Rajabi, Armin; Selamat, Nor Fazilah Mohamad; Sajuri, Zainuddin; Omar, Mohd. Zaidi.

In: Materials Science and Engineering A, Vol. 754, 29.04.2019, p. 728-734.

Research output: Contribution to journalArticle

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AB - Al6061 is a heat-treatable aluminum alloy and an extremely versatile material used in settings where medium to high strength is required. To produce good joints using this alloy, a particular solid-state welding process called friction stir welding (FSW) is preferable instead of the conventional welding methods. In this study, the effects of T6 post-weld heat treatment (PWHT) on the mechanical properties, dislocation density, and microstructure of a friction stir welded (FSWed) Al6061 aluminum alloy were investigated. Results indicated that FSW had degraded the mechanical properties of Al6061. The welding efficiency decreased to 65% compared with the tensile strength of the base metal. After FSW, the samples demonstrated a serrated flow behavior known as the Portevin–Le Chatelier (PLC) effect. This effect was attributed to the nonuniform distribution of hard Mg 2 Si particles, coarsening and/or solutionizing of the strengthening elements in the stir and thermomechanically affected zones, and an over-aging effect in the heat-affected zone of the FSWed sample. However, the T6-PWHT performed on the FSWed sample diminished the PLC effect and concurrently improved the mechanical properties back to its original state. The PWHT also promoted precipitation hardening through a better distribution of Mg 2 Si particles that prevented grain growth and increased the dislocation density due to the applied strain, which subsequently improved the mechanical properties of the FSWed Al6061 alloy.

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