LARGE STRAIN WORK HARDENING AND SOFTENING OF ALUMINIUM ALLOYS - A MICROSTRUCTURAL MODELLING APPROACH

The work hardening behaviour of some non-heat treatable aluminium alloys is followed up to large strains. The evolution in strength and microstructure during cold rolling is analysed in commercially pure aluminium, AlMg and AlMn alloys, covering a wide range of solid solution levels. A recently developed model for work hardening is applied and discussed in relation to the experimental observations. At large strains, stage IV, an unexpectedly low work hardening rate of high-Mg alloys is observed. This is further discussed in terms of TEM and EBSD observations on the cold rolled material. The low work hardening rate of high-Mg alloys is ascribed to a different storage pattern of dislocations caused by an increased amount of shear bands and a higher dislocation density inside subgrains. Work softening of aluminium alloys is also discussed in terms of the misorientation evolution.