A comprehensive study on fused filament fabrication of Ti-6Al-4V structures

In metal additive manufacturing, microstructural inhomogeneities, like anisotropic mechanical strength and geometric limitations in directed energy deposition, electron beam melting, or selective laser sintering, have led to the exploration of alternative techniques in recent years. Among these techniques, fused filament fabrication is an attractive alternative due to its successes in producing dense parts, approaching traditional manufacturing specifications. Despite this success, many challenges remain to produce reliable parts with reproducible properties using FFF, particularly in the thermal treatment for part densification. Here are presented results of using a polyolefin-based binder system loaded with 55-59 vol. % Ti-6Al-4V powder to create a printable filament. Printed Ti-6Al-4V parts using these filaments were sintered at temperatures ranging from 900 to 1340 °C and evaluated by x-ray diffraction, scanning electron microscopy and optical microscopy. The sintered samples demonstrated a linear decrease in v-phase from 15 to 11 vol. % with increasing temperature, while residual stress and Young's modulus increased. Additionally, the density of printed and sintered Ti-6Al-4V parts could be increased up to 91 % of the theoretical density of Ti-6Al-4V by increasing the sintering temperature up to 1340 °C. Samples that were sintered at 1340 °C showed a higher Young's modulus compared to SLM samples, likely due to the increased a-phase in samples sintered at 1340 °C.