Effect of Structural-Phase State on the Deformation Behavior and Mechanical Properties of Near β Titanium Alloy VT22 in the Temperature Range 293–823 K

This paper investigates the effect of thermomechanical treatments, including deformation by radial shear rolling or severe plastic deformation by abc pressing with subsequent aging at 773 K, on the structural-phase state, deformation behavior, and mechanical properties of commercial near β titanium alloy VT22 (Ti–5Al–5Mo–5V–1Cr–1Fe). The structure of the alloy after radial shear rolling and subsequent aging consists of transformed β grains with a lamellar α + β structure and primary α-phase particles. Severe plastic deformation of the alloy followed by aging causes the formation of a grain-subgrain α + β structure with an average characteristic size of 0.23 µm. It is found that, after the thermomechanical treatments, the strength characteristics of the alloy at room temperature increase by ~40% compared to the as-received alloy. The alloy after radial shear rolling and aging retains a 40–20% higher strength in the temperature range of 293–823 K. The strength of the alloy after severe plastic deformation and aging becomes lower than that of the as-received alloy already at a temperature of 773 K. Analysis of creep parameters at 743 K shows that the creep deformation of the alloy in the state after radial shear rolling and aging occurs by the motion of dislocations (glide + climb). The creep deformation of the alloy in the state after severe plastic deformation and subsequent aging is largely contributed by grain boundary sliding.