Efficiency of the strengthening of titanium and titanium alloys of various classes by the formation of an ultrafine-grained structure via severe plastic deformation

The efficiency of strengthening induced by microstructure refinement to an ultrafine-grained (UFG) state is studied on commercial purity VT1-0 titanium and two-phase VT6 and VT22 titanium alloys. An UFG structure with a grain size <0.5 μm is formed by multiaxial isothermal deformation. The refinement of a titanium microstructure to a grain size of ∼0.4 μm is found to result in an almost twofold increase in the strength and the fatigue limit. The strength of a VT22 alloy with an UFG structure is equal to that of the thermally strengthened alloy. The strength and fatigue limit of a VT6 alloy with an UFG structure are higher than those of the thermally strengthened state by approximately 25%. The strengthening by microstructure refinement is found to be expedient for low and medium alloys.