On the mechanical behaviour of titanium alloy TiAl6V4 manufactured by selective laser melting: Fatigue resistance and crack growth performance

Direct manufacturing (DM), also referred to as additive manufacturing or additive layer manufacturing, has recently gained a lot of interest due to the feasibility of producing light-weight metallic components directly from design data. Selective laser melting is a very promising DM technique for providing near net shape components with relative high surface quality and bulk density. Still, process induced imperfections, i.e. micron sized pores and residual stresses upon processing, need to be considered for future application, e.g. in the aerospace and biomedical sectors. Moreover, fatigue loading is a critical scenario for such components and needs to be investigated thoroughly. Consequently, the current study aims at establishing sound microstructure–defect–property relationships under cyclic loading for a TiAl6V4 alloy processed by selective laser melting. Employing mechanical testing, hot isostatic pressing, electron microscopy and computer tomography it is shown that the micron sized pores mainly affect fatigue strength, while residual stresses have a strong impact on fatigue crack growth.

► Microstructure – fatigue property relationships are established for SLM–Ti-6-4.
► Ti-6-4 directly following SLM is very brittle, heat treatment increases ductility.
► Process-induced pores can be eliminated by hot isostatic pressing (HIP).
► Fatigue strength is mainly affected by residual porosity.
► Crack growth behaviour is mainly affected by residual stresses.