Influence of exposure in a corrosive environment on ultimate stress of heat-treated welded joints of Al–Mg–Si–Сu alloy

Abstract

Abstract The priority task of modern aircraft construction is to ensure the reliability of the operation of structures, which depends both on the quality of execution of technological processes during manufacturing and on the corrosion-mechanical durability of welded joints. This work aims to study the influence of contact duration with a corrosive environment on the mechanical strength of the base metal and welded joints of the Al–Mg–Si–Cu alloy, heat-treated in different modes (artificial aging, quenching followed by artificial aging). Corrosion-mechanical tests were carried out under constant axial tensile stress in 3 % NaCl solution for 14 days, followed by determination of the corrosion rate, ultimate strength, and fractographic analysis of the fracture surface. The results showed that the corrosion resistance of the joints is almost equal to the corrosion resistance of the base metal. It was experimentally confirmed that the ultimate strength of the base metal and welded joints decreased after corrosion exposure in a 3 % NaCl solution. This is caused by the embrittlement of the structure and the formation of corrosion defects in the near-surface zone during contact with a corrosive environment, which led to a change like a fracture from ductile to ductile with brittleness.