Friction stir welding was carried out on non-heat treatable aluminium alloy AA5083-H111, rolled to a thickness of 4 mm. The rotation speed was 1120 rpm and the travel speed was 320 mm/min in all the welds. Two different shoulder geometries (smooth concave, striated flat) were used with a cylindrical pin M5 threaded with 3 flats with a length of 3.9 mm. Intergranular corrosion tests following the ASTM G67 and exfoliation corrosion tests following the ASTM G66 were performed on parent material and samples of the two different welding conditions. Metallurgical features, such as the diffusion of initial precipitates, the changes of grain size in the heat-affected zone and thermal-mechanically affected zone are investigated. Metallographic analysis reveal the small coalescence of grains and the reduction of precipitates in the grain boundaries of the HAZ and TMAZ which play an important role in the prevention of corrosion development. The fact that all the weld affected zones present hardness values higher than the parent material allow to conclude that, at least under static load, the failure would occur in the parent material zone. The loss mass in the parent material samples is higher than in the welded samples because the intergranular corrosion mechanism is more susceptible at the intergranular precipitates, and these are more abundant in the parent material. The exfoliation corrosion tests demonstrate that corrosion resistance of the AA5083-H111 is better when welded with the smooth concave shoulder due to better surface finishing of the weld bead. Thus, the higher roughness at the top of the weld bead resulting from the striated flat shoulder promotes the earlier start and faster development of the corrosive attack. From the SEM analysis it was confirmed that the parent material presents a preferential morphology to intergranular attack, while the attack that occurs in the HAZ and weld bead is not so concentrated and less significant.
Metallurgical and corrosion features of friction stir welding of AA5O83-H111
Welding in the World ; 50 , 9/10 ; 55-64
2006
10 Seiten, 24 Bilder, 3 Tabellen, 16 Quellen
Article (Journal)
English
British Library Conference Proceedings | 2007
|FRICTION STIR WELDING MACHINE, AND FRICTION STIR WELDING SYSTEMS WITH SUCH MACHINE
European Patent Office | 2016
|SAE Technical Papers | 2007
|Friction Stir Welding and NASA
NTRS | 2016
|