Effect of galvanic coupling on the corrosion susceptibility of friction stir weldment of AA2198-T851 alloy
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2018
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CONGRESSO BRASILEIRO DE ENGENHARIA E CIÊNCIA DOS MATERIAIS, 23.
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The AA2198-T851 alloy is a new generation Al-Li alloy which finds application in the
aerospace industry. Its preference over conventional Al alloys is premised on the fact
that it exhibits better strength to weight ratio and improved fatigue resistance due to
the addition of Li as a major alloying element. However, it is a relatively new alloy and
its processing-structure-property-performance relationship is far from being
established. This is very true for the relationship between its structure and corrosion
resistance which is very scarce in the literature. Our recent findings have revealed that
this alloy is highly susceptible to severe localized corrosion which is caused by the
abundance of active hexagonal T1 (Al2CuLi) particles in its microstructure. The
corrosion susceptibility is further promoted by the non-uniform precipitation of these
particles which are often preferentially concentrated in bands aligned parallel to the
{111}Al. Furthermore, bulk zonal heterogenities with pronounced non-uniform
distribution of the active T1 particles are created when this alloy is welded using friction
stir welding. The friction stir welding process is a solid state welding process that has
been adjudged to be the best welding technique for Al alloys. Nonetheless, this process
generates different zones in the weldments of Al alloys. Thus, zones exhibiting different
electrochemical characteristics and severe galvanic interactions can occur when the
weldment is exposed to a corrosive media. The galvanic interactions can lead to a
faster propagation of attack in the most susceptible region of the weldment, which in
this case is the parent material (with the highest volume fraction of the T1 particles).
To establish this, the galvanic interactions between the zones of the weldment have
been investigated by separately exposing the parent material and the stir zone of the
weld and then by exposing the entire weldment using NaCl and EXCO solutions.
Optical, scanning electron and transmission electron microscopes were also employed
in the study. The results revealed that the parent material of the weldment was the
most susceptible (as previously mentioned) and appeared to corrode at a faster rate
when coupled to the more cathodic stir zone, thermomechanically affected zone and
the heat affected zones of the weldment (with lower volume fraction of the T1 particles).
The modes of corrosion in the zones of the weld were also observed to be different.
However, the most susceptible region corroded intragranularly with the grain
boundaries exhibiting more noble electrochemical characteristics.
Como referenciar
COSTA, I.; DONATUS, U.; MILAGRE, M.X.; MACHADO, C.S.C.; ARAUJO, J.V.S. Effect of galvanic coupling on the corrosion susceptibility of friction stir weldment of AA2198-T851 alloy. In: CONGRESSO BRASILEIRO DE ENGENHARIA E CIÊNCIA DOS MATERIAIS, 23., 04-08 de novembro, 2018, Foz do Iguaçu, PR. Resumo... p. 5232-5232. Disponível em: http://repositorio.ipen.br/handle/123456789/29574. Acesso em: 30 Dec 2025.
Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.