Effect of specimen thickness on fatigue crack growth behavior of friction stir welded 6063-T5 aluminum alloy

Abstract

In this study, the effect of specimen thickness on the fatigue crack growth behavior of the friction stir welded (FSW) joints of 6063-T5 aluminum alloy was investigated. Generally, based on microstructure characterization of welded zone, three different zones have been classified, i.e., stir zone (SZ), thermo-mechanically affected zone (TMAZ) and heat-affected zone (HAZ). The crack growth behavior in the SZ was examined. In addition, the fatigue tests on the base materials (BM) of 6063-T5 aluminum alloy were carried out. The specimens with two different thickness were prepared for both the friction stir welded joints (SZ specimen) and the base materials (BM specimen). The fatigue crack propagated along the welding direction in the SZ specimen and the rolling direction in the BM specimen. Fatigue tests were conducted at the stress ratio R=0.1 under axial loading. The crack growth rate was accelerated as the specimen thickness increased and the thickness effect was more significant in the stir zone. In the SZ specimen, the crack growth rate of the thick specimen is approximately three times higher than that of the thin specimen except lower stress intensity factor range. In the BM specimen, the fatigue crack growth rate of the thick specimen is slightly higher than that of the thin specimen.

Keywords

• fatigue
• crack growth
• thickness effect
• friction stir welding
• aluminum alloy