The effects of pre-deformation on the creep aging behavior and mechanical properties of Al-Li-S4 alloys

In the present work, the effects of pre-deformation on the creep ageing and associated mechanical properties were investigated regarding Al-Li-S4 alloys. It was found that pre-deformation caused significant reduction in the creep strain, but enhancement in the tensile strength. Meanwhile, a “multi-step stage” feature of the creep strain response was observed during creep ageing. The microstructural evolution at different stages were examined accordingly using transmission electron microscope (TEM). Two strengthening precipitates were identified, including the tetragonal θ′ (Al2Cu) and T1 (Al2CuLi) phases. Both were further analyzed with respect to their sizes (length and thickness) and volume fractions during creep ageing. Additionally, pre-deformation initiated some lath-shaped s'(Al2CuMg) precipitates, as confirmed using high-angle annular dark filed (HAADF) imaging and energy dispersive spectroscope (EDS). This work indicates that novel Al-Li-S4 alloys, with improved mechanical properties, can be obtained through manipulating and introducing pre-deformation to the creep ageing.