Abstract
Microstructure changes in the 2618 aluminium alloy during. creep-fatigue tests were studied. These tests simulate the conditions of the application of this alloy in devices for the exhaustion of hot gasses generated during fire in closed or difficultly accessible areas.
Creep-fatigue tests result in high dislocation density in subgrains and narrow subgrain boundaries, in contrast to creep tests reported in our previous work where large subgrains were observed with relatively wide subgrain boundaries and relatively low dislocation density in grains. Extensive precipitation occurred with denuded (precipitate-free) zones along grain boundaries.
The coherent S-phase (Al2CuMg) transformed into partially coherent needle-shaped S' precipitates. Superior stress amplitude caused reduced lifetime and wider denuded zones.
A model of the formation of denuded zones along (sub)grain boundaries was proposed.