Structural and phase transformations in a titanium alloy of the transition class under the effect of deformation

Abstract

Structural and phase transformations in the VT22 (α + β) titanium alloy of the transitional class that occur during cold plastic deformation (CPD) by upsetting under the conditions of limited friction have been studied and the evaluation of the nonuniformity of deformation along the height of the deformed samples has been performed. It has been found that a CPD of the alloy quenched from the β field with degrees of reduction higher than 6% results in the formation of a martensite-like τ phase (bct) with an axial ratio c/a less than 1; upon upsetting with reductions exceeding 16%, α″ martensite appears in the structure. It is shown that the structural transformations in the alloy with the above degrees of deformation are realized in the following sequence: easy slip (ɛ = 1.5%); multiple slip (ɛ = 6%); the formation of a cellular structure (ɛ = 16%); the formation of deformation twins (ɛ = 23% and higher). The morphology of phases and structural constituents at all stages of the alloy treatment has been established and the distribution of the degree of deformation over the height of the deformed samples has been calculated.