3D reconstruction of prior β grains in friction stir-processed Ti-6Al-4V.

The prior β grain structure and orientations in the central stir zone of friction stir-processed Ti-6Al-4V were reconstructed from measured α phase orientations obtained by three-dimensional serial sectioning in a dual-beam focused ion beam scanning electron microscope. The data were processed to obtain the α colony and β grain size distributions in the volume. Several β grains were individually analysed to determine the total number of unique α variants and the respective volume fractions of each. The analysis revealed that some grains experienced overwhelming variant selection (i.e. one variant dominated) whereas other β grains contained a more evenly distributed mixture of all 12 variants.