The coupling effect of particle and electric current on the grain refinement of Al–Cu–Li alloy by an improved thermo-mechanical treatment with electrically-assisted annealing

Abstract

An improved thermo-mechanical treatment with electrically-assistant recrystallization annealing (EARA) was proposed for Al–Cu–Li alloy with the fine and equiaxed grains. The Al–Cu–Li alloy strips were subjected to the different overaging times, asymmetric rolling and EARA. The size and number of particles had a significant effect on the average grain size. The critical particle size for particle-stimulated nucleation (PSN) was determined. The introduction of electric current did not change the critical size, however, the efficiency of PSN triggered by coarse particles was improved by 3.6 times, compared with the conventional recrystallization annealing (CRA). By the optimized overaging time, the grains were refined and the texture was weakened. The recrystallization mechanism for the specimens containing coarse particles was the discontinuous static recrystallization (DSRX) by PSN and the continuous static recrystallization (CSRX). At the constant current density and annealing time, the critical temperature for rapid recrystallization for EARA decreased by 40 °C, compared with CRA. The results were due to the local Joule heating effect, the activation energy reduction and atomic diffusion rate increase by the athermal effect of electric current. The improved RI-ITMT with EARA would be an ideal candidate for rapid grain refinement in Al–Cu–Li alloy alloys.