Effects of two-stage creep-aging on precipitates of an Al–Cu–Mg alloy

Creep-aging forming, combining the aging treatment and forming process, is an ideal method to manufacture the complex aircraft panels. Two-stage creep-aging behaviors of an Al–Cu–Mg alloy are studied by uniaxial tensile creep tests over wide ranges of temperature and external stress. Effects of creep-aging temperature and external stress on precipitates are discussed. The results show that the formation of substantial nuclei occurs in the first creep-aging stage. With the increases of creep-aging temperature and external stress in the second creep-aging stage, the precipitates easily grow up, while the density of precipitates first increases and then decreases. Meanwhile, the width of precipitate free zone and the size of grain boundary precipitate increase. Compared with the stress-free aging process, the two-stage creep-aging process broadens the width of precipitate free zone, and result in the discontinuously-distributed aging precipitates along grain boundaries, which can improve the corrosion resistance of the studied Al–Cu–Mg alloy.