Evolution of grain-scale microstructure during large strain simple compression of polycrystalline aluminum with quasi-columnar grains: OIM measurements and numerical simulations

Polycrystalline deformation acid its modeling by currently used crystal pla sticity models has been investigated by means of an experiment involving di rect measurement of deformation induced orientation changes. The experiment used a polycrystalline aluminum sample with quasi-columnar grains, whose i nitial lattice orientations were mapped using the Orientation Imaging Micro scopy (OIM) technique. The sample was then compressed 40% (along the axis o f the columnar grains), and the lattice orientations after deformation were studied by OIM. It was found that most of the grains had significant in-gr ain misorientations in the form of deformation bands with two morphologies - either elongated on the grain scale or nearly equiaxed. In many, but not all cases, more than one similarly oriented deformation band was found in a n individual grain. The deformation was then simulated using (i) a classica l Taylor-type model, and (ii) a finite element model of the polycrystalline aggregate imposing equilibrium and compatibility between and within the co nstituent grains (in the weak numerical sense). A comparison of the predict ions with the experimental results indicated that the Taylor-type model cap tured well the tendency to move towards a < 110 > fiber texture but Failed to predict correctly which < 110 > pole was rotating towards the compressio n axis in the individual grains, and also by its implicit assumptions could not predict any in-grain misorientation. The finite element model predicte d, reasonably well. grain rotations as well as the magnitude of the in-grai n misorientations in most, but not all, of the individual grains, but faile d completely to predict the morphology of the deformation bands that develo ped within the grains. (C) 2001 Elsevier Science Ltd. All rights reserved.