Effect of Wall Thickness Transitions on Texture and Grain Structure in Additive Layer Manufacture (ALM) Ti-6Al-4V

In titanium alloys it is known that in bulk sections the solidification conditions in ALM commonly lead to undesirable, coarse, columnar beta grain structures. Here, we have investigated the effect of build geometry on the grain structure and associated texture in Ti-6Al-4V ALM components produced by Selective Electron Beam Melting (SEBM). Through reconstruction of the primary beta-phase, it has been confirmed that in thick sections large columnar beta grains grow with a strong < 001 >(beta) fibre texture, although there is a significant skin effect. In contrast, in thin walls nucleation off the surrounding powder and growth inwards dominates. Local heterogeneities are also observed within section transitions. It is shown that the weaker alpha transformation texture arises from a random distribution across the possible habit variants.