Effect of Corrosion and Surface Finishing on Fatigue Behavior of Friction Stir Welded EN AW-5754 Aluminum Alloy Using Various Tool Configurations

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%.

Modeling of Heat Energies and Forces in Friction Stir Welding

“…The energy values of a welding process were calculated in each stage using reward calculation techniques. An optimal method to estimate the energy emitted by the welding probe during contact with the workpiece and correlate it with the welding forces at each stage has been proposed [14]. Different stiffener shapes were simulated on panels.…”

Advances in friction stir welding by separate control of shoulder and probe

“…1a) is known for a simple design and process handling, in which the shoulder and probe have the same rotational speed and direction (n probe = n shoulder ). This simplicity has made it the most commonly used configuration in FSW despite the rough periodic surface structures and inferior mechanical fatigue properties [3,11]. Recent investigations are extensive and pointing thematic priorities such as weld seam properties of similar and dissimilar materials, varying probe/shoulder geometries, tool wear, and the interactions between tool and FSW setup [4,6,7,12,13].…”

“…Only the probe rotates and generates the total frictional heat input (n shoulder = 0, compare Fig. 1b) [11]. Due to the absence of the shoulder generated heat input, comparatively higher probe rotational speeds are necessary.…”

“…This means in particular the upward material flow in the stationary shoulder, which features a drain movement from the process zone through the gap between the probe and stationary shoulder up to a designated outlet port [9]. Current investigations with stationary shoulder configuration focus mostly the mechanical and physical weld seam properties [11,14,15].…”

Corrosion Behavior of Cold-Formed AA5754 Alloy Sheets

“…Due to their high mechanical and anti-corrosion properties, low density, and good formability, the 5xxx series of Al alloys is widely used in many branches of industry, particularly in the automotive industry [1][2][3][4][5][6]. Their chemical composition mainly includes Al and Mg (up to 7 wt.% Mg), along with secondary additions of Mn and trace amounts of Cr [7].…”