Enhanced fatigue characteristics of a topology-optimized porous titanium structure produced by selective laser melting

The fatigue properties are critical considerations for porous structures, and most of the existing porous materials have unsatisfactory performances due to a lack of structural optimization. This work shows that a topology-optimized structure fabricated by selective laser melting using commercial-purity titanium (CP-Ti) exhibits excellent fatigue properties with an ultra-high normalized fatigue life of ∼0.65 at 10⁶ cycles and at a low density of 1.3 g/cm³. The main factors affecting fatigue, i.e., material properties and a porous structure were studied. Both the factors can affect the fatigue crack initiation time, thereby affecting the fatigue life. Because of twinning that occurred during the fatigue process, the porous CP-Ti samples exhibit a high plasticity. In addition, the fatigue crack propagation rate is significantly reduced because of the high plasticity of the CP-Ti material and the occurrence of fatigue crack deflection.