Metal Additive Manufacturing Conference - MAMC 2022

Mechanical behavior of additive manufactured Nb-Ti and Ti-Nb-Zr alloys using plasma atomized and HDH powders
Mário Boccalini Jr., Railson B. Falcão, Marcelo F. Moreira, Fernando J. G. Landgraf, Moysés L. de Lima

Monotonic mechanical properties of beta Nb-48%Ti and martensitic Ti-13%Nb-13%Zr alloys processed through Laser Powder Bed Fusion (LPBF) with two different types of powder, spherical plasma atomized powder (PA) and irregular shaped powder produced by Hydrogenation-milling-dehydrogenation process (HDH), are compared.
Twenty cylinders with 12 mm diameter and 92 mm length were produced through LPBF in a SLM-Cusing M2 machine (5 for each alloy/powder set), under argon atmosphere with oxygen content controlled to be less than 0.1%. Laser power and scanning speed were selected based on achievement of porosity below 0.5%: both powders of Nb-48%Ti alloy were cast using 300W and 1100mm/s, while powders of Ti-13%Nb-13%Zr alloy were cast using 200W and 1000mm/s for PA powder and 200W and 1000mm/s for HDH powder. All samples were produced with the same scanning strategy, that is, 4 mm islands in a chess pattern with 90 degrees rotation of the tracks in each layer with Z direction perpendicular to the longitudinal axis of the cylinders. The four operation platforms were heat treated for stress relief at 650⁰C for two hours before removing the cylinders through wire electro discharge machining.
All cylinders were post-processed with turning to obtain specimens for tensile tests performed with universal machine.
For both alloys, specimens cast with HDH powder presented higher strength and lower ductility than the specimens cast with PA powder. This is attributed to the solid solution hardening promoted by the higher oxygen content of the HDH powder.
Fracture analysis was performed in order to correlate mechanical properties with fractographic and microstructure features of the alloy/powder sets.