EBSD characterisation and modelling of columnar dendritic grains growing in the presence of fluid flow
Résumé
Columnar dendritic grains of steel grown in the presence of fluid flow (e.g. solidified on turning rolls) have been characterised by Electron Backscattered Diffraction (EBSD) technique. It is shown that grains have a random crystallographic orientation at the surfaces of the sheet in contact with the mould. In the middle of the sheet, the grains which have survived the growth selection mechanisms exhibit a 〈100〉 texture in which the average dendrite trunk direction is not exactly aligned with the thermal gradient (i.e. the normal to the surfaces of the sheet). It is tilted by about 15° toward the upstream direction. This deviation is examined by simulations of grain structure formation based on a three-dimensional Cellular Automaton (CA)–Finite Element (FE) (3D CAFE) model, which has been modified in order to account for fluid flow effects. The modified CA algorithm includes a growth kinetics of the dendrites which is a function of both the undercooling and fluid flow direction. It is validated by comparing the predicted shape of an individual grain growing under given thermal and fluid flow conditions with an analytical solution. The 3D CAFE predictions of the columnar grains grown in the presence of fluid flow are in good agreement with the experimental EBSD results.