EFFECT OF HIGH-TEMPERATURE DEFORMATION ON THE TEXTURE OF A 2-PHASE TITANIUM-ALLOY

Changes in the texture of both the alpha- and beta-phases of the two-phase alloy Ti-6Al-4V have been determined in order to clarify the mechanisms of high-temperature deformation. A strain of approximately 1.5 was applied to the alloy at 928-degrees-C, at strain rates representative of superplastic and non-superplastic conditions. The alpha-phase texture changed very little with strain rate whereas that for the beta-phase was much more sensitive. The beta-phase texture was weakened at superplastic strain rates but developed a fibre texture at non-superplastic rates. It is postulated that under superplastic conditions the alloy deforms predominantly by grain boundary sliding of the soft beta-phase grains, with the hard primary alpha-phase grains remaining in their original orientations and the measured loss in texture intensity being attributed to the loss in texture of the secondary alpha-phase only. Under non-superplastic conditions there is a greater contribution from plastic deformation in the beta-phase which, in turn, can enhance the secondary alpha-phase texture.