Microstructure and mechanical characterizations of additively manufactured high oxygen-doped titanium

In the present work, an additive manufacturing method of selective laser melting (SLM) was adopted to produce high oxygen-doped commercial purity titanium (Ti-O), with raw materials of high purity Ti and rutile (TiO₂) powders. Microstructure and mechanical characterizations were then applied to the materials, which indicates that the TiO₂ powders decompose under the SLM process and the oxygen atoms presented as solid solutes. Uniaxial quasi-static and dynamic compressive experiments suggest that the strength of SLM Ti-O drastically increases regardless of loading rate, yet the strain rate sensitivity is quite distinguished for pure Ti and the Ti-O alloy. Namely, strain rate jump tests demonstrated positive values of strain rate sensitivity for both samples, while under dynamic loading the Ti-O alloy and pure Ti exhibit obvious strain rate softening and strain rate hardening, respectively. The difference between these two SLM samples is then found to closely relate with their microstructures. Finally, a theoretical model is proposed to elucidate the abnormal strain rate softening.