TiB reinforced Ti-6Al-4V matrix composites with improved short-term creep performance fabricated by laser powder bed fusion

Abstract

This study investigates the short-term creep performance of laser powder bed fusion (L-PBF) fabricated Ti-6Al-4V (Ti64) and TiB-reinforced Ti64 matrix composite (TMC) parts. The TMCs were fabricated by L-PBF processing of 0.2wt.%B4C/Ti64 composite powder. The optimum set of process parameters was used to manufacture creep test specimens. In addition to the as-built scenario, supertransus heat treatment was conducted to eliminate the microstructural anisotropy. Creep testing of the as-built and heat-treated samples was performed at 600 °C under a constant tensile stress of 200 MPa. Microstructural evolutions were scrutinized before and after the creep test. Results revealed a slightly longer rupture time for Ti64 than the TMC part in the as-built state. Although the boundaries of prior β grains were detected as the preferential void nucleation sites in both as-built samples, the TMC part featured a significantly higher frequency of smaller voids near the fracture location. The heat-treated Ti64 sample showed the most inferior creep performance with a premature failure due to continuous networks of grain boundary α (GB-α). However, the heat-treated TMC counterpart showed a noticeably improved creep performance with a rupture time of 5.8 h owing to the absence of GB-α, presence of hard and stiff TiB reinforcements, and the increased fraction of interfaces (α-α, α-β, and α-TiB).