Predicting Properties of Bulk Ti-6Al-4V Produced Via Directed Energy Deposition

Advanced manufacturing approaches, including additive manufacturing (i.e., “3D printing”) of metallic structures requires informed qualification, whereby models are integrated that can predict the chemistry, microstructure, and resulting material properties. In this work, we present such a modeling approach for the Electron Beam Additive Manufacturing process, a type of Directed Energy Deposition, culminating with a series of constitutive equations that are used to predict the yield strength of Ti-6Al-4V subjected to one of three different heat-treatments: a stress relief anneal in the α+β phase field; a hot isostatic press treatment in the α+β phase field; and a β-anneal. The equations are nominally identical, though different strengthening mechanisms are active according to subtle microstructural differences. To achieve an equation that can predict the yield strength of the material, it is necessary to include an assessment of a knock-down effect on tensile strength due to texture. This has been experimentally measured, and included in this paper. The predictions of yield strength are generally within 5% of their experimentally measured values.