Simultaneously enhancing strength and ductility of LPBF Ti alloy via trace Y2O3 nanoparticle addition

Laser powder bed fusion (LPBF) is a popular additive manufacturing (AM) technique to fabricate metal components. LPBF Ti alloys often exhibit high strength but poor ductility. In this study, we report that trace Y2O3 nanoparticles added to a pre-alloyed Ti-4Al-4V (Ti44) powder provides an excellent feedstock for LPBF. As-built Ti44-Y2O3 materials exhibited a strength-ductility combination that is slightly better than heat-treated LPBF Ti64. Some Y2O3 particles may have melted or decomposed during LPBF. From electron microscopy, the addition of Y2O3 refined α' martensite laths and weakened variant preference during β→α' transformation. Based on in situ synchrotron X-ray diffraction and elastic-viscoplastic self-consistent (EVPSC) modeling, slip was more active in as-built Ti44-Y2O3 than in as-built Ti64 or Ti44. This work demonstrates that LPBF can be an excellent method to fabricate metal-nanoparticle composite materials.