Materials Science Forum, Vol.495-497, 663-668, 2005
beta ->alpha(s) variant selection in sharp hcp textured regions of a bimodal IMI834 billet
Regions with sharp local textures, called macrozones, have been characterised in a bimodal IMI834 billet, containing 30% of primary alpha(p) grains surrounded by secondary as colonies. It is shown that the as colonies have been inherited according to a strong variant selection during the beta ->alpha(s) phase transformation. In each observed macrozone, the favoured variants have in average their c-axes in the same; macroscopic direction as the aP grains. A detailed analysis of neighbouring aP grains and as variants clearly shows that the variants favoured at beta/alpha(p) boundaries are those able to share their c-axes with a neighbouring alpha(p) grain. The sharpness of such a variant selection mechanism is strongly related to the local orientation distribution of neighbouring alpha(p)/beta grains at high temperature. This explains the differences in variant selection sharpness observed from one macrozone to the other.