Integration of Deformation Processing with Additive Manufacture of Ti-6Al-4V Components for Improved β Grain Structure and Texture

Abstract

With Ti alloys like Ti-6Al-4V, the solidification conditions across virtually all AM platforms lead to strongly textured, coarse columnar, β grain structures. Transformation to α on cooling dilutes the texture, but significant texture is still inherited which contributes to undesirable anisotropy in AM parts. In the work presented a deformation step has been integrated into the manufacture of components produced by the blown powder method, using an Ultrasonic Impact Treatment (UIT), which has the additional benefit of reducing residual stresses. It has been found that the introduction of surface deformation to each layer can lead to a greatly refined grain structure with a more randomised texture. To investigate the origin of this effect, reconstruction of the β grain structure and texture from the α EBSD measurements has been used to characterise the high temperature β microstructure.