3D characterisation of early twin formation in Ti-4Al by diffraction contrast tomography

Twin formation in alpha-Ti is a topic of much debate as the role of micro structure features and alloy chemistry on twin formation remains unclear. In the present work, early stage of twin formation, i.e. after 1% plastic compression, has been studied in3D using diffraction contrast tomography. This technique has enabled to study a volume about 400 grains enabling statistic al analysis. The family of twinned grains was compared with similarly orientated grains that had not twinned in respect of their neighbourhood and grain size. While the initial neighbour hood analysis did not identify any significant differences, 3D grain size analysis highlighted that grain size plays an important role during the early stage of twinning. Further, twin clusters/chains were identified, which form slightly imperfect 3D networks. A more detailed neighbourhood analysis of the parent grains associated with the twin clusters/chains demonstrate that strain localization in neighbouring grains well aligned for prismatic <a> slip transfer promote the observed twin clustering.