On the deformation mechanism of ultrafine-grained titanium with multilayered hierarchical structure

The ultrafine-grained Ti with a multilayered hierarchical structure (MHS) has been fabricated by using cryorolling combined with surface mechanical attrition treatment technique. The deformation behavior of this material is a result of superimposition of the different structural layers (and their interfaces) each of which has its specific deformation and failure mechanism. The deformation mechanisms include copious shear banding in the outer amorphous/nanocrystallite layer, grain boundary mediated deformation in the nanograined layer and shear localization in the ultrafine-grained core. The mechanical gradations in the junctions between layers are believed to be responsible for the mitigated interface failure pattern, crack-stopping effect and the enhanced loading resistance. Such a complex plastic deformation processes operating within the individual layers benefits the high strength and work hardening of the MHS Ti.