Calculation of the parent hcp grain orientation from inherited variants in the hcp to t and in the hcp to cc phase transformations -: Application to the α-γ transformation in TiAl-based alloys

The orientations of the inherited tetragonal (resp. cubic) variants are calculated from the parent hcp orientation in the case of a strict orientation relation. The numbering of the variants is proposed, as well as the misorientations between them. Conversely, a method for calculating the parent hcp orientation from a sufficient number of inherited variants is proposed. It is based on orientation correlating and orientation averaging, and it is particularly useful when the inherited variants are not exactly related to the parent orientation by a strict orientation relation or when the orientations of the inherited volumes slightly vary at different locations of the variant. The method is illustrated by considering the alpha to gamma phase transformation taking place in TiAl-based alloys