Papers by Keyword: AA6056

Abstract: Sheet materials of the alloys 6056 and 2024A were joined using the friction stir welding technique. Similar and dissimilar butt welds were produced. Strength and corrosion behaviour of the joints were investigated in different heat treatment conditions. Hardness profiles across the weld revealed minima in the heat affected zones, being very pronounced at the advancing side of the joints. The hardness of the nugget zone increased after post-weld artificial aging. Strengths of postweld heat treated similar 6056 and dissimilar 2024A/6056 joints approached 90 and 85 %, respectively, of the ultimate tensile strength of 6056-T7X. As found by electrochemical measurements, alloy 2024A-T3 exhibited the most noble corrosion potential and artificially aged alloy 6056 the most active potential. Besides microstructural changes caused by the welding process, galvanic coupling affected the corrosion behaviour of friction stir welds, in particular with joints of dissimilar aluminium alloys, as indicated by accelerated corrosion of alloy 6056 in the nugget region. Intensified corrosion attack was also observed in the heat affected zones.

Abstract: The Russian 1370 Al-Mg-Si-Cu alloy (analogue of 6056) is an advanced material for the skin and stringers of fuselage. However, these alloys are susceptible to the intercrystalline corrosion depending on the heat treatment regimes. The investigations of the effect of heating temperature during the solid solution treatment (530-555)°C and quenching rate, ageing regimes and interval between the quenching and ageing on the structure and properties of 1370 alloy sheets were performed. The strengthening β (Mg2Si) -phase and Q (Al5Cu2Mg8Si6) -phase relationship dependence of the alloy properties is established. Using the dark field electron microscopy which permits to intensify separate diffraction reflexes of strengthening phases the structure of Q-phase precipitates has been studied. Optimization of heat treatment of 1370 alloy sheets provided the combination of fracture toughness characteristic (Kco= 100 MPa√m) high level, the ultimate strength of 400-420 MPa and intercrystalline corrosion no more 100 μm in depth.