Interpretation of the fatigue anisotropy of additively manufactured TA6V alloys via a fracture mechanics approach

This work is focused on the influence of porosity when dealing with the fatigue behaviour of TA6V alloys fabricated by the selective laser melting (SLM) process. The presence of porosity is one of the major issues facing additive manufacturing (AM) of metallic components subjected to fatigue loading. In order to study the effect of porosity on the fatigue behaviour, a vast experimental campaign has been undertaken. Seven specimen batches, fabricated by the SLM process with different building directions (horizontal, vertical and diagonal) were tested and a large amount of data was obtained. The link between the applied stress, the fatigue life and the pore size is highlighted by using generalized Kitagawa-Takahashi maps. It is shown that the effect of porosity on the fatigue strength is much more pronounced compared to the effect of the microstructure. In the modelling section, two approaches based on fracture mechanics are considered. The first one is based on the Paris law which is used to model long fatigue crack growth. The second approach was proposed by Caton et al. (2001) for modelling small fatigue crack growth. Finally, a simulation of the generalized Kitagawa-Takahashi is presented and good agreement with the experimental data is shown.