Finite element modelling of hot rolling of Al-3%Mg and the kinetics of static recrystallisation

The principal objectives of this work were (i) to investigate the effect of geometry on the through-thickness gradient in microstructure evolved during post-deformation annealing treatment of rolled AI-3%Mg slabs and (ii) to employ the finite element method and empirical equations characterising the rate of static recrystallisation to predict the gradient in the volume fraction recrystallised through the slab thickness. Geometry was characterised by the aspect ratio of the deformation zone. The finite element method was used principally to simulate the evolution and spatial distribution of process parameters namely the strain, strain rate and temperature of deformation through the rolled slab thickness. Standard metallographic techniques and quantitative metallography combined with optical microscopy under polarised light were employed to measure the volume fraction recrystallised. The geometric orientation of microbands developed due to hot deformation was also characterised. Rate-dependent, thermomechanical material constitutive data based on the hyperbolic sine and Voce type of flow stress/strain relationships were used as input in the two-dimensional finite element model together with a friction model based on the penalty method. Published empirical equations linking the rate of static recrystallisation and the process parameters were then employed to predict the measured volume recrystallised. Results indicated that gradients in microstructure occurred through the rolled slab thickness for all the slab/geometry and rolling conditions considered and that the orientation of microbands developed independent of the rolling reduction. The main conclusions drawn were that (i) geometry had a profound effect on the evolution of microstructure through the rolled slab thickness; (ii) the finite element method can be used as an effective tool in the prediction of through-thickness gradient in microstructure evolved in the post-deformation annealing treatment; and (iii) microband development was an important microstructural feature during hot rolling of AI-3%Mg, acting as potential nucleation sites for subsequent static microstructural transformation processes. (author)Available from British Library Document Supply Centre-DSC:DXN045785 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo