Effects of temperature and shielding gas mixture on fatigue life of 5083 aluminum alloy

A fatigue crack develops as a result of stress concentration and extends with each load cycle until failure occurs, or until the cyclic loads are transferred to redundant members. The fatigue performance of a member is more dependent on the localized state of stress than the static strength of the base metal or the weld metal.

This is a study of fatigue strength of Al5083-O aluminum alloy to investigate influence of fatigue life on welding zone according to the mixing shield gas ratio and the test temperature. The GMAW was carried out for weld specimens with various mixing shield gas ratios (Ar100% + He0%, Ar67% + He33%, Ar50% + He50%, and Ar33% + He67%). The test temperatures for the fatigue test were +25 ◦C (+77 ◦C), −30 ◦C (−22 ◦C), −85 ◦C (−121 ◦C), and −196 ◦C (−321 ◦C). The welding zone was divided into four subzones for analysis; weld metal, fusion line, HAZ, and base metal according to the notch position. Regarding the influence on the bead shape of the mixing shield gas ratio, the bead width was greatest in Ar100% + He0% mixture. But the bead depth and area were greatest in Ar33% + He67% mixture. The dilution was also best in the mixing shield gas ratio. In the influence of mixing gas ratio, fatigue life of weld metal specimens decreased with higher argon gas ratio, but fusion line and HAZ specimens were not influenced greatly. Also, the fatigue life increased at lower temperatures, particularly at −196 ◦C.

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