Microstructure and Salt Fog Corrosion Behaviour of AA2219 Friction Stir Welded Aluminium Alloy

• Дата: 2015
• Автори: Srinivasa Rao, G., Subba Rao, V.V., Koteswara Rao, S.R.
• Формат: Стаття
• Мова: English
• Опубліковано: Інститут металофізики ім. Г.В. Курдюмова НАН України 2015
• Назва видання: Металлофизика и новейшие технологии
• Теми: Дефекты кристаллической решётки
• Онлайн доступ: http://dspace.nbuv.gov.ua/handle/123456789/111889
• Назва журналу: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Цитувати: Microstructure and Salt Fog Corrosion Behaviour of AA2219 Friction Stir Welded Aluminium Alloy / G. Srinivasa Rao, V. V. Subba Rao, S. R. Koteswara Rao // Металлофизика и новейшие технологии. — 2015. — Т. 37, № 4. — С. 539-554. — Бібліогр.: 41 назв. — рос.

Aluminium alloy 2219 is a favourite age hardenable alloy considered for fabrication of earth storable and cryogenic propellant tanks of launch vehicles. In the current study, 8.1 mm thick AA2219-T87 aluminium alloy plates are joined using friction stir welding. Friction stir welding produces three different microstructural zones, and these zones exhibit different microstructural characteristics. Therefore, it is expected that the various zones will exhibit different corrosion susceptibility. The corrosion behaviour of the base material and friction stir welded joints is investigated using salt fog test (ASTM B117) at different pH value and spraying times. Optical microscopy and transmission electron microscopy are used to observe the corrosion attack at various zones of the weld. As observed, the welds exhibit excellent corrosion resistance in basic and neutral solution than in acidic solution. As found, the corrosion rate decreases with increase in time of exposure at all pH values. As observed, the corrosion rate is predominant in acidic solution for first 24 hrs of spraying time. As found, the corrosion attack is greater in the base material than weld metal at all pH value and spraying times. Within the weld, the heat-affected zone (HAZ) is found to be more susceptible to corrosion compared to the weld nugget and thermomechanically affected regions. The results obtained from the transmission electron microscopy confirm that the increased rate of corrosion of HAZ in acidic solution is due to the precipitation of second phase particles (CuAl₂) at the grain boundaries causes depletion of copper near the grain boundaries, making these regions anodic to the grain centre.