Microstructure and mechanical properties of friction stir welded aluminium alloys with special reference to AA 5083 and AA 6082

Abstract

Aluminium alloys AA 5083 and AA 6082 have been friction stir welded and the mechanical properties and microstructures of the welds have been evaluated. Alloy AA 5083 mainly fractured near the centre of the weld, while fracture in AA 6082 mainly occurred in the heat affected zone. The tensile strength of welded joints in AA 6082 was lower than the base material strength, but still met classification societies’ requirements. Hardness was approximately constant across the welded zone in AA 5083, while a minimum in hardness was found in the AA 6082 welds. The location of the fracture closely matched the minimum hardness region. Very fine scale precipitation in AA 6082 was significantly affected by the weld thermal cycle. In the zone of lowest hardness, the hardening precipitate ( β″-Mg5Si6) had transformed to the non-hardening β′-Mg1.7Si. This is probably the main reason for the minimum in hardness, the fracture location, and the decreased tensile strength. Results are compared to a similar investigation of aluminium alloy AA 7075.

Effect of Welding Parameters on Weld Formation and Mechanical Properties in Dissimilar Al Alloy Joints by FSW

“…The average tensile strength approached approximately 90% of that of the 5052 alloy, regardless of the material arrangement, but the tensile strengths of the AS5052-RS5J32 joints were slightly higher than those of the AS5J322-RS5052 joint. This is consistent that for the solid-solution-hardened aluminum alloys, such as 5XXX series, FSW did not result in softening of the welds, 15,16) the locations of the two dissimilar alloys exerted a significant effect on the resultant weld quality, and the low strength material should be placed on the advancing side to produce better welds. 19) However, the elongation was decreased compared with that of the 5052 alloy for both material arrangements.…”

“…Aluminum alloys are classified into precipitation-hardenable alloys and solid-solution-hardenable alloys, and it was reported that the softening of the welds did not occur during FSW for the solid-solution-hardenable alloys. 15,16) For the AS5J32-RS5052 joints in Fig. 3, the hardness values of the SZ were slightly higher than those of the 5J32 base materials.…”

Numerical Study of the Mechanical Behavior and Fatigue in a Weld Bead by Friction Stir for a 6082-T6 Aluminum Alloy

“…In [9] and [20], it is suggested that the variation of the microhardness values in the welded area and parent material is due to the difference between the microstructures of the base alloy and weld zone. Pictures of the microstructure of the different areas of the 6082-T6 alloy aluminum can be found in [21].…”

Effect of rotation speed on nugget structure and property of high rotation speed friction stir welded Al-Mn aluminum alloy

“…Since the increase of grain size tends to reduce the hardness according to the Hall-Petch relationship, the hardness improvement at higher rotation speeds should be induced by high distribution densities of substructures rather than the coarsened grains. The dislocation-dominant strengthening mechanism for nugget zone was commonly observed in the C-FSW of aluminum alloys [25,26], and this study demonstrates that it can also be present in the HRS-FSW of aluminum alloys.…”