Abstract
In this study, fatigue behavior of surface finished and precorroded friction stir welded (FSW) specimens using various tool configurations were comparatively investigated by the load increase method. The FSW using conventional, stationary shoulder and dual-rotational configurations was carried out by a robotized tool setup on 2 mm EN AW-5754 aluminum sheets in butt joint formation. After extraction of the specimens, their weld seam and root surfaces were milled to two different depths of 200 µm and 400 µm to remove the surface and the FSW tool shoulder effects. This surface finishing process was performed to investigate the effect of the surface defects on the fatigue behavior of the FSW EN AW-5754 aluminum alloy sheets. It was found that material removal from the weld and root surfaces of the specimens, increased the fracture stresses of conventional and dual-rotational FSW from 204 to 229 MPa and 196 to 226 MPa, respectively. However, this increase could not be detected in stationary shoulder FSW. Specimens with finished surfaces, which showed superior properties, were used in salt spray and cyclic climate change test to investigate the effect of corrosion on the fatigue behavior of FSW specimens. It was shown that cyclic climate change test reduced the fatigue properties of the base material, conventional, stationary shoulder and dual-rotational FSW approximately 1%–7%. This decrease in the fatigue properties was greater in the case of the salt spray test, which was 7% to 21%.
Highlights
The joining of light metals has always been a challenge for lightweight construction industries that have high demands on the reliability and efficiency of joining technologies
This is an important issue due to the fact that the weld zone is considered critical as the weakest site within the component and should receive more attention. It becomes even more critical when the weld is subjected to a corrosive environment as this has a detrimental effect on the fatigue life of entire structures by causing premature failure of components in service [31]. Another less studied aspect of friction stir welded (FSW) EN AW-5754 aluminum alloy joints are the effect of surface finishing on their fatigue properties, which can present a good solution for the components, which are subjected to extraordinary loads, repeated for millions of cycles in extreme environmental conditions [32]
The present study aimed to investigate the influence of various tool configurations and the related surface defects on the fatigue behavior of FSW welded EN AW-5754 aluminum alloy
Summary
The joining of light metals has always been a challenge for lightweight construction industries that have high demands on the reliability and efficiency of joining technologies. It becomes even more critical when the weld is subjected to a corrosive environment as this has a detrimental effect on the fatigue life of entire structures by causing premature failure of components in service [31] Another less studied aspect of FSW EN AW-5754 aluminum alloy joints are the effect of surface finishing on their fatigue properties, which can present a good solution for the components, which are subjected to extraordinary loads, repeated for millions of cycles in extreme environmental conditions [32]. The present study aimed to investigate the influence of various tool configurations and the related surface defects on the fatigue behavior of FSW welded EN AW-5754 aluminum alloy (compare Figure 2).
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