Mechanical properties and corrosion resistance of Al–Cu–Mg–Ag heat-resistant alloy modified by interrupted aging

Abstract

Abstract The effects of interrupted aging on the microstructure, mechanical properties and corrosion resistance of Al–Cu–Mg–Ag heat-resistant alloy were investigated by hardness tests, tensile tests, exfoliation corrosion (EXCO) tests, transmission electron microscopy (TEM) and electrochemical analysis. Results showed some phases precipitated during the interrupted aging process in Al–Cu–Mg–Ag alloy, which were called secondary precipitations. The precipitations both in the grains and the grain boundaries were refined by interrupted aging. The phases on the grain boundaries of the single-aged sample were distributed discontinuously, whereas those of the interrupted-aged sample were chain-like with a wider precipitation free zone (PFZ) on both sides of the grain boundary. The elongation of Al–Cu–Mg–Ag alloy increased by 37.7% while the tensile and yield strength slightly decreased after interrupted aging. The corrosion resistance of Al–Cu–Mg–Ag alloy was mainly determined by the PFZ with the lowest self-corrosion potential. The coarse and discontinuously distributed precipitations on the grain boundaries of the single-aged sample gave rise to larger efficient PFZ width than that of the interrupted-aged sample, which then lead to wider corrosion passageway and resulted in the better exfoliation corrosion resistance of Al–Cu–Mg–Ag alloy treated by interrupted aging.