The Influence of the Content of Alloying Elements in Titanium Alloys Ti–6Al–4V and Ti–4Al–3V on the Macro- and Microstructure in Wire–Feed Electron Beam Additive Manufacturing

Abstract

This paper outlines the results of investigating the structural arrangement at different scales in additively manufactured Ti–6Al–4V and Ti–4Al–3V titanium alloys. The research indicates that both alloys display a notable anisotropy of structural and mechanical properties that is more pronounced in the alloy with reduced aluminum and vanadium levels. Increasing the alloying element content results in reduced grain size in the titanium alloy and alters its structural and phase characteristics. The development of a complicated structure comprising α₂-Ti₃Al, α''-Ti, and β-Ti phases in the α/β-lath structures results in enhanced strength characteristics of the Ti–6Al–4V alloy in comparison with the Ti–4Al–3V alloy, in which the primary structural elements following printing consist of the α-phase with a minor fraction of β-Ti phase interlayers. The alloys exhibit pronounced anisotropy in their mechanical response during quasistatic tensile tests as well as in fatigue and impact toughness evaluations. In tensile testing, the Ti–4Al–3V alloy samples tested in the diagonal direction display the greatest strength and the lowest ductility, while those tested in the growth direction show the lowest strength and the greatest ductility. The same tendency is also observed with the Ti–6Al–4V alloy, although it is less distinct. Although the average tensile strength of the Ti–6Al–4V alloy samples exceeds that of the Ti–4Al–3V alloy by over 200 MPa and the micro–hardness value by more than 1.0 GPa, the Ti–4Al–3V alloy demonstrates reasonable printability characteristics and can be utilized for producing components via the WEBAM method due to its lower cost.