Development of grain misorientation texture, in terms of coincident site lattice structures, as a function of thermomechanical treatments

Abstract

Microtexture (i.e. grain-specific) measurements have been made from grains both before and after grain growth in an austenitic stainless steel. Such measurements allow computation of grain misorientation texture in terms of the proportions of coincident site lattice (CSL) boundaries. After 2% postrecrystallization strain the grain growth is surface initiated in this alloy, and so, during the grain growth incubation period t_o, data were acquired just from those grains contiguous with the free surface. A clear trend emerged that the proportion and clustering of CSLs (particularly ‘special’ types which tend to have higher than average mobilities) increased both during t_o and after t_o when grains were actually growing. The CSL fractions were consistently greater for surface than for interior grains. It is therefore proposed that firstly the clustering of CSLs at surface grains is instrumental in the initiation of anomalous grain growth and secondly the nature of the grain misorientation texture after substantial anomalous growth was found to be a function of the precise thermochemical treatment. Thus it becomes feasible to exploit the link between CSL fraction and processing route in order to obtain a grain-boundary population of predetermined misorientation, and therefore to obtain some control over boundary properties.