Precipitation in Al–Cu–Mg alloy during creep exposure

The uniaxial tensile creep tests of Al–Cu–Mg alloy were carried out over a wide range of temperature and applied stress. The effects of applied stress and creep aging temperature on the precipitation in Al–Cu–Mg alloy were discussed. It is found that the precipitation process is very sensitive to the applied stress and creep aging temperature, and S phase (CuMgAl2) is the main precipitate under the tested creep conditions. With the increase of applied stress and creep aging temperature, S phase easily grows up and becomes sparse. Meanwhile, the creep aging leads to the discontinuous distribution of precipitation phase in grain boundary, which can improve the corrosion-resistance of Al–Cu–Mg alloy. Because the lattice misfit of acicular exudation phase is far less than that of disk-shaped phase, the applied stress/strain fields will alert the competitive precipitation equilibrium between different strengthening phases. So, the large applied stress and high aging temperature easily make the preferential precipitation process as SSS→GPB→S″→S′→S.