Predicting tensile properties of Ti-6Al-4V produced via directed energy deposition

TLDR

Additive manufacturing of metallic structures requires new qualification strategies, and informed qualification uses modeling to predict material characteristics such as tensile properties for given chemistries and microstructures. The study develops constitutive equations to predict the yield strength of additively manufactured Ti‑6Al‑4V under three heat‑treatments. The equations are based on nominally identical constitutive models that account for different strengthening mechanisms and a texture‑induced knock‑down effect, which was experimentally measured and incorporated. Predicted yield strengths are within 5 % of experimentally measured values.

Abstract

Advanced manufacturing approaches, including additive manufacturing (i.e., "3D printing") of metallic structures requires a change to qualification strategies. One approach, informed qualification, integrates modeling strategies to make predictions of material characteristics, including the prediction of tensile properties for given chemistries and microstructures. In this work, constitutive equations are developed and presented that can predict the yield strength of additively manufactured 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 also necessary to include an assessment of dramatic reduction in the tensile strength due to texture (i.e., a "knock-down" effect). This has been experimentally measured, and included in this paper. The resulting predictions of yield strength are generally within 5% of their experimentally measured values.