Characterisation and modelling of the evolution in microstructure and properties during plastic deformation of aluminium alloys

The work hardening and the microstructure evolution of three alloys, AlMg0.5, AlMg1 and AlMg3, have been examined during cold rolling to large strains. A commercially pure aluminium alloy, AA1050, has also been considered for the case of comparison. It was expected, and predicted by the ALFLOW model, that the stage IV work hardening rate should depend on the stage III-IV transition stress, a prediction confirmed by experimental observations. Beyond the III-IV transition, however, it is found that the slope of the flow curves converges towards a common thetaIV, i. e. unaltered by the Mg content. Explanations for this behaviour are searched for in the microstructure. Subgrains (size and misorientation), grain break-up and shear bands are studied in light microscope, SEM and TEM. The grain break-up is quantified by using orientation imaging mapping in the SEM. The break-up varies with initial grain size but shows no clear dependence on neither solute content nor cold rolling strain for epsilon>0.5-1. Neither the subgrain misorientation seems to depend on the solute content. The amount of shear bands increases with strain and solute content, and may provide a plausible explanation for the convergence towards a common thetaIV-value.