Achieving High Fatigue Resistance in Titanium Alloys Through Near-porosity-free 3D Printing

The advantages of 3D printing - i.e., additive manufacturing (AM) of structural materials - have been seriously compromised by their disappointing fatigue properties. Often, the poor fatigue performance seems to be due to the presence of microvoids induced by current printing process procedures. We therefore ask the question whether the elimination of such microvoids can provide a viable solution to significantly improve the fatigue resistance of pore-free AM (net AM) alloys. Here, we successfully reconstruct a nearly void-free AM microstructure in a Ti-6Al-4V titanium alloy developed by the development of a Net-AM processing technique, by understanding the nonlinearity of phase transformations and grain growth. We determine the fatigue resistance of such AM microstructures and show that they lead to high fatigue limits of approximately 1 GPa, exceeding the fatigue resistance of all AM and wrought titanium alloys as well as other metallic materials. We confirm the high fatigue resistance of the Net-AM microstructure and the potential advantage of AM processing in producing structural components with maximum fatigue strength, which is beneficial for the further application of AM technology in the engineering field.