Changes in the Structural-Phase State and Mechanical Properties of VT35 Alloy After Severe Plastic Deformation and Subsequent Annealing

The influence of severe plastic deformation and subsequent pre-recrystallization annealing on the structural-phase state and mechanical properties of the VT35 titanium alloy is studied. It is shown that the formation of an ultrafine-grained structure leads to a 65−75% increase of the room-temperature mechanical properties of this alloy compared to its initial coarse-grained state. A significant scatter in the mechanical properties of the alloy after such treatment is attributed to the inhomogeneity of the α and β phase distribution in the bulk of the workpieces. A subsequent pre-recrystallization annealing of the VT35 ultrafine-grained alloy at the temperatures of 723 and 773 K leads to an additional increase in its mechanical properties (the yield strength and ultimate tensile strength values can exceed 1700 MPa). Using the samples annealed at 723 K for 0.5 h as an example, it is shown that this increase is accounted for by a larger volume fraction of the α-phase due to the β→α phase transformation occurring inside the β phase regions and, hence, a more uniform α and β phase distribution.