Laser beam welding and friction stir welding of 6013-T6 aluminium alloy sheet

Abstract

Butt welds of 1.6 mm thick 6013‐T6 sheet were produced using laser beam welding and friction stir welding processes. Employing the former joining technique, filler powders of the alloys Al‐5%Mg and Al‐12%Si were used. Microstructure, hardness profiles, tensile properties and the corrosion behaviour of the welds in the as‐welded condition were investigated. The hardness in the weld zone was lower compared to that of the base material in the peak‐aged temper. Hardness minima were measured in the fusion zone and in the thermomechanically affected zone for laser beam welded and friction stir welded joints, respectively. Metallographic and fractographic examinations revealed pores in the fusion zone of the laser beam welds. Porosity was higher in welds made using the filler alloy Al‐5%Mg than using the filler metal Al‐12%Si. Transmission electron microscopy indicated that the β″ (Mg2Si) hardening precipitates were dissolved in the weld zone due to the heat input of the joining processes. Joint efficiencies achieved for laser beam welds depended upon the filler powders, being about 60 and 80% using the alloys Al‐5%Mg and Al‐12%Si, respectively. Strength of the friction stir weld approached over 80% of the ultimate tensile strength of the 6013‐T6 base material. Fracture occurred in the region of hardness minima unless defects in the weld zone led to premature failure. The heat input during welding did not cause a degradation of the corrosion behaviour of the welds, as found in continuous immersion tests in an aqueous chloride‐peroxide solution. In contrast to the 6013‐T6 parent material, the weld zone was not sensitive to intergranular corrosion. Alternate immersion tests in 3.5% NaCl solution indicated high stress corrosion cracking resistance of the joints. For laser beam welded sheet, the weld zone of alternately immersed specimens suffered severe degradation by pitting and intergranular corrosion, which may be associated with galvanic coupling of filler metal and parent material.

Mechanical Properties and Microstructural Evolution of Friction-Stir-Welded Thin Sheet Aluminum Alloys

“…The heat of friction and plastic flow arising from the rotating tool produces significant microstructural changes, which lead to local variations in the mechanical properties of the weld. [1][2][3][4][5] FSW is being targeted by the industry for structurally demanding applications to provide high-performance benefits. [6] The weld zone consists of a stir zone, a thermomechanically affected zone (TMAZ), and a heataffected zone (HAZ).…”

Structure‐property investigations on a laser beam welded dissimilar joint of aluminium AA6056 and titanium Ti6Al4V for aeronautical applications Part I: Local gradients in microstructure, hardness and strength

“…Grain boundary liquation is typical [29][30][31][32][33] to butt joints of laser beam welded 6XXX Alalloys that are welded by the keyhole mode. In the present case energy input was not that high due to the heat conduction mode.…”

Aluminum friction stir welds: Review of fatigue parameter data and probabilistic fracture mechanics analysis

“…Fig. 14 shows a similar histogram and lognormal distribution for 60xx Al [114][115][116][117][118][119]8,29,28,120,121,34,9,41,50,102,122,123,44,124,46,17,125,126,48,127,112] with l = 78.7 andr = 15.5.…”