Effect of Heat Input on the Microstructure and Phase Composition of Additively Manufactured Ti–6Al–4V Alloy

Abstract

Optical microscopy and X-ray phase analysis are used to investigate the grain structure and phase composition of Ti–6Al–4V titanium-alloy samples produced by wire-feed electron beam additive manufacturing using a linear strategy. X-ray fluorescence analysis is employed to examine the elemental composition of the Ti–6Al–4V alloy samples fabricated through 3D printing. The samples are rectangular plates cut from bars, which are produced under varying thermal-exposure parameters, specifically different beam currents and 3D-printing speeds. We compare the elemental composition of the printed Ti–6Al–4V samples with that of the wire from which they were produced. The effect of heat-input magnitude on the sizes of primary β‑phase grains and α-phase plates in the samples and the volumetric fraction of the residual β phase is determined. We demonstrate how the sizes of primary β-phase grains and α-phase plates, along with the volumetric fraction of the residual β-phase, change with increasing distance from the contact point of the samples with the substrate. We propose hypotheses regarding the causes of these changes. The effect of the substrate on the elemental and phase composition of the samples is also shown.