Dislocation-Induced Precipitation and Its Strengthening of Al–Cu–Li–Mg Alloys with High Mg

Abstract

Generally, the good combination of pre-deformation and aging can improve the mechanical strength of the Al–Cu–Li–Mg alloys. However, the effects of pre-deformation on competitive precipitation relationship and precipitation strengthening have not been clarified in detail in Al–Cu–Li–Mg alloys with high Mg. In the present study, the effects of pre-deformation level on the microstructure and mechanical properties of an Al–2.95Cu–1.55Li–0.57Mg–0.18Zr alloy have been investigated. It is found that the introduction of dislocation by 5% pre-deformation can facilitate the precipitation of new successive composite precipitates and T₁ precipitates along the sub-grain boundaries or dislocations and inhibit the precipitation of dispersive GPB zones which is the main precipitates of the alloys without pre-deformation. The introduction of 5% pre-deformation can enhance the mechanical properties considerably. When the pre-deformation level increases from 5 to 15%, the number density of the successive composite precipitates and T₁ precipitates increases, and the aspect ratio of T₁ precipitates decreases. The decrease in T₁ precipitate aspect ratio and the increment of the successive composite precipitates result in the reduction in precipitation strengthening. Therefore, the increase in pre-deformation level from 5 to 15% does not further improve the mechanical properties of the alloys, although the dislocation strengthening increases continuously.