Texture heterogeneities induced by subtransus processing of near α titanium alloys

Clusters of α grains with sharp local texture, called macrozones, have been observed in titanium products and reported to reduce the fatigue performances. This work investigated how these macrozones form during manufacturing so that their development can be avoided. It mainly focused on the role of the α/β deformation step. This step converts the lamellar microstructure into equiaxed primary αp grains and secondary αs lamellar colonies inherited from the β to α transformation. A lamellar TIMETAL 834 alloy was compressed and annealed in the α/β domain. Orientation maps were acquired and combined with the corresponding microstructure to characterize the αp/αs microtexture. Moreover, advanced orientation data processing was applied to evaluate the final αp/β microtexture at the deformation temperature. The results showed that α/β processing produced macrozones of αp grains and αs colonies. The mechanisms by which they formed are investigated.