Effect of Cold Rolling Reduction on Precipitation of Al20Cu2Mn3 Particles in Al-Cu-Mn System Alloys

Abstract: Problem. The influence of the degree of cold deformation on the morphology and precipitation of T-phase particles (Al20Cu2Mn3) in Al–Cu–Mn system alloys (ALTEK) during final annealing has been insufficiently studied. This complicates the prediction of properties and the optimisation of thermomechanical processing of sheets and foils for electrical engineering applications. Objective. To establish the patterns of the influence of the cold rolling deformation degree (50 and 90 %) on the formation, morphology, and size of T-phase (Al20Cu2Mn3) particles, as well as on the complex of mechanical and electrical properties of sheets and foils made of ALTEK alloy of the Al–2%Cu–2%Mn system, produced by the following scheme: hot rolling → cold rolling → annealing at 400 C. Methods. Ingots were produced by chill casting and subjected to hot rolling, intermediate annealing, and cold rolling. A portion of the specimens was annealed at 400 °С for 3 hours. The microstructure was studied using transmission electron microscopy. Electrical conductivity (EC) and mechanical properties were measured. Results. It was found that the majority of Al20Cu2Mn3 particles is formed during hot rolling. Cold deformation causes dislocation hardening and fragmentation of existing particles. Regardless of the degree of deformation (50 or 90 %), annealing at 400 °С forms an identical microstructure with lamellar T-phase precipitates measuring 120–200 nm. The electrical conductivity increases from 14.6–14.8 MS/m to 29.6 MS/m after annealing. Conclusions. The degree of cold deformation in the investigated range does not affect the volume fraction of T-phase particles after annealing. The main increase in electrical conductivity and softening are caused by a reduction in dislocation density and further decomposition of the solid solution with coagulation of particles formed during the hot rolling stage.