Mechanical properties and fracture modes of thin butt-joined aluminum-steel blanks for automotive applications

Zahra Silvayeh*, Josef Domitner, Christof Sommitsch, Matthias Hartmann, Werner Karner, Bruno Götzinger

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

The influence of different filler alloys and joining parameters on the mechanical properties and on the fracture modes of aluminum-steel blanks for automotive applications was experimentally investigated. Sheets of 1.15-mm-thick aluminum alloy EN AW-6014 T4 were butt-joined with sheets of 0.80-mm-thick zinc-coated steel DC04 using the single-sided Cold Metal Transfer (CMT) process. The quasi-static strength and the fracture modes of the joints were determined using uniaxial tensile and three-point bending tests. The width of the heat-affected zone (HAZ) was estimated based on hardness profiles and maps. The microstructure inside the HAZ was studied using optical micrographs, and selected fracture surfaces were investigated by means of scanning electron microscopy (SEM). The influence of the filler alloy composition was more significant under tensile load than under bend load. Under tensile load three different fracture modes depending on the actual location of fracture were identified. The most brittle behavior of the joint was observed, if fracture occurred directly at the weld seam. Both, thickening of the intermetallic (IM) layer between the weld seam and the steel sheet as well as the porosity forming during the joining process, facilitated fracture at the weld seam. Most favourable combinations of strength and ductility under both tensile and bend loads were obtained when using comparatively silicon-rich filler alloys Al-3Si-1Mn or Al-1Si-Mg-Mn at the welding speed of 0.4 m/min. Increasing the welding speed to 0.7 m/min may still result in acceptable strength and ductility of the joints; however, further increase to 1.0 m/min reduces these properties considerably.
Original languageEnglish
Pages (from-to)456-467
JournalJournal of Manufacturing Processes
Volume59
DOIs
Publication statusPublished - Nov 2020

Keywords

  • Aluminum-steel blanks
  • Automotive industry
  • Butt joint
  • Car body
  • Cold Metal Transfer (CMT)
  • Fracture modes
  • Lightweight design
  • Mechanical properties
  • Welding-brazing

ASJC Scopus subject areas

  • Industrial and Manufacturing Engineering
  • Strategy and Management
  • Management Science and Operations Research

Fields of Expertise

  • Mobility & Production

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