Ageing response of cold-rolled Al-Cu-Mg alloy

This work presents a detailed investigation of the ageing behaviour of AA2519 alloy subjected to cold rolling with reduction of 10-80% (epsilon similar to 0.11-1.61). The impact of pre-straining level and ageing duration on the mechanical performance was elucidated via hardness and tensile testing, DSC and analytical TEM. The increasing rolling reduction followed by ageing reduces the peak age hardening and pronounces softening under over-ageing. This effect of pre-strain on mechanical properties is related to the dependence of a dispersion of plate-shaped precipitates that form on the {001}(alpha) and {111}(alpha) planes on deformation structure. The results show that prior plastic strain profoundly changes kinetics of the ageing reaction and precipitation sequence. The peak age hardening is provided by the dense and homogeneous precipitation of a theta'-phase, while the over-ageing is attribute to the concurrent precipitation of the.-phase on boundaries and thickening theta'-phase plates on dislocations. In addition, an theta-phase platelets appear during ageing; however, its number density is insufficient to affect the mechanical properties, significantly.