Texture and Crystal Orientation in Ti-6Al-4V Builds Fabricated by Shaped Metal Deposition

Abstract

The texture and crystal orientation of Ti-6Al-4V components, manufactured by shaped metal deposition (SMD), is investigated. SMD is a novel rapid prototyping tungsten inert gas (TIG) welding technique leading to near-net-shape components. This involves sequential layer by layer deposition with repeated partial melting and heat treatment, which results in epitaxial growth of large elongated prior β grains. This leads to a directionally solidified texture, where the prior β grains exhibit only a small misorientation with each other. The β grains grow in $\left\langle { 100} \right\rangle$ direction with a second $\left\langle { 100} \right\rangle$ direction perpendicular to the wall surface. During cooling, the α phase transformation follows the Burgers orientation relationship leading to a Widmanstätten structure, with orientation relations between most of the α lamellae and also of the residual β phase. The directionally solidification and the transformation into the α phase following the Burgers relationship results in a texture, where the hcp pole figures look similar to bcc pole figures.