The effect of preliminary treatment with subsequent aging on structural-phase state and mechanical properties of β titanium alloy

Abstract

The effect of aging at 723 K on the structural-phase state and mechanical properties of VT35 titanium alloy after β quenching and various treatments using severe plastic deformation has been studied. It is shown that annealing at 1073 K followed by quenching and aging leading to the precipitation of large α-phase lamellae with volume fraction of 20 % doesn’t have a strengthening effect on the alloy. After processing by radial shear rolling and subsequent aging fine α-phase precipitations in the form of plates and nanometer-sized particles with a volume fraction of 24 % are observed in β-phase grains. However, large areas of β-phase without α-phase precipitates are observed. The strength properties of the alloy after the treatment increase by 40 – 45 %. The processing by the method of multiple pressing leads to the formation of a mixed α / β UFG structure with a grain / subgrain size of 0.11 µm. Subsequent aging leads to the decomposition of the residual β-phase and to a homogeneous distribution of α and β phases in the alloy with volume fraction of α-phase 51 %. The formation of such an UFG structural-phase state leads to an increase in the strength properties of the alloy by a factor of almost two compared to the initial state.