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Material models and mechanical properties of titanium alloys produced by selective laser melting

Modeling of additively manufactured (AM) titanium alloys behavior in loading conditions represents a step forward to understand its advantageous and favorable properties in various applications, such as medical implants, components for aerospace, automotive and process industry. The knowledge on its behavior is very limited, especially if the focus is directed to modeling of the behavior of titanium alloys produced by selective laser melting (SLM), which opens many possibilities in achieving optimal design of titanium alloy components. Therefore, an overview of the expected properties of these materials has been performed, in order to choose or develop appropriate material mod-els suitable for their behavior modelling. By adapting existing or developing new constitutive material models, in further work the behavior of SLM antibacterial Ti-xCu titani-um alloys will be modelled considering their microstructure and defects. In this study, state-of-the-art on mechanical properties of AM Ti6Al4V alloy is given, as well as exist-ing constitutive material models developed for metallic materials. The following three factors have the greatest influence on the anisotropic behavior of AM metallic materials: microstructure, porosity orientation and residual stresses. The microstructure after SLM of the Ti6Al4V alloy consists predominantly of martensite (α') within long columnar prior β grains, resulting in a high yield strength of about 1000 MPa and a low elongation of less than 10%. The pores within the material have a great influence on the high cycle fatigue performance of the material, and the crack initiation phase can be significantly extended only by reducing the porosity. The fatigue strength of the horizontally and the vertically oriented samples during AM at 10^7 cycles is below 300 MPa and 350 MPa, which is 62.5% and 56.25% lower than the wrought Ti6Al4V material respectively. By reducing the residual stresses without changing the microstructure, it was found that the residual stresses have a greater influence on the propagation of the crack than the microstructure itself. The results of this study will consider the guidelines and recommendations on the properties for SLM-ed titanium alloy samples production, as well as references for the appropriate material models development for their behavior modeling.

Selective laser melting ; Ti6Al4V ; Ramberg – Osgood parameters

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