Effect of oxygen content in feedstock powders on microstructure and mechanical properties of ELI Ti-6Al-4V fabricated via laser powder bed fusion

Extra low interstitial (ELI)-grade Ti-6Al-4V powder—known for its low oxygen content—is commonly employed for additive manufacturing. However, its impurity content depends on the processing conditions or the manufacturer. This study investigated the effects of the oxygen content on the microstructural characteristics and mechanical properties of Ti-6Al-4V samples produced through laser powder bed fusion. The microstructure of the samples was analyzed through various spectroscopic techniques, and X-ray diffraction analysis was conducted to assess the lattice parameter differences. Vickers hardness measurements were performed to evaluate the mechanical properties of the samples. While the porosity of all samples remained low and exhibited little correlation with the oxygen content, an increase in oxygen content resulted in greater lattice distortion and a higher Vickers hardness. Additionally, the thickness of alpha laths was reduced after hot isostatic pressing treatment. These findings suggest that the presence of oxygen in ELI-grade powder significantly affects the microstructure and mechanical properties.