Mechanical properties and microstructure of heterogeneous commercial pure titanium prepared by rotary swaging and annealing

The industrial applications of commercial pure titanium (CP-Ti) are significantly limited due to the strength-ductility trade-off in metallic materials. The strategy of heterostructured materials has been proposed to design microstructures for desired strength and ductility. To improve the mechanical properties of CP-Ti, a heterostructured rod, consisting of ultrafine fibrous grains and recrystallized grains, was produced by rotary swaging and subsequent annealing. The heterostructured Ti exhibits a high tensile strength of 636 MPa, simultaneously sustaining a high ductility of 11.9%, its tensile toughness is three times that of the swaged sample. The superior mechanical properties are attributed to the significant hetero-deformation induced (HDI) hardening in heterostructured Ti. It is found that the HDI hardening is induced by the interactions between geometrically necessary dislocations (GNDs) and hetero-interfaces.