Very high strain rate deformation twinning behaviour of Ti-6Al-4V

Equiaxed fine-grained and coarse-grained samples of h.c.p. alpha phase Ti-6Al-4V with trace amounts of retained b.c.c. beta phase were ballistically tested at room temperature. The deformed microstructures were characterised by electron back scattered diffraction. The extensive deformation twinning observed in the.. phase in both samples was limited to the {10 (1) over bar2} and {11 (2) over bar1} tensile twinning modes. These two deformation twinning types have very different morphologies: thin {11 (2) over bar1} deformation twins span multiple alpha phase grain boundaries, while the wider {10 (1) over bar2} deformation twins are usually limited to individual grains, reorienting almost entire grains to a twinned orientation. Both {10 (1) over bar2} and {11 (2) over bar1} deformation twins are able to propagate across low angle alpha lath boundaries, but only the {11 (2) over bar1} deformation twinning types can propagate across high angle alpha grain boundaries.