Huang, S., Kumar, P., Yeong, W. Y., Narayan, R. L., & Ramamurty, U. (2022). Fracture behavior of laser powder bed fusion fabricated Ti41Nb via in-situ alloying. Acta Materialia, 225, 117593. https://doi.org/10.1016/j.actamat.2021.117593
Abstract:
The microstructures and the mechanical properties, including fatigue crack growth (FCG) and mode I fracture toughness (KIC), of in-situ alloyed Ti41Nb (wt.%) fabricated using the laser powder bed fusion (LB-PBF) were investigated. A small hatch spacing - fast scanning strategy was utilized for obtaining parts with minimum porosity and unmelted Nb particle combination. The mesostructure of the fabricated blocks comprises columnar grains with alternating Nb-poor regions (NPRs), which occur due to the short residence time of materials in the melt that limits the melting and diffusion of Nb, and matrix layers. Extensive ωiso precipitates were noted in the microstructure, which were attributed to the large-build related heat accumulation during the LB-PBF process that stems from the combination of large sample size and high energy density input. Consequently, ductility of the as-built parts was low. The FCG rate at high ΔK was strongly influenced by the layers of NPR and hence depend on the orientation whereas the near-threshold FCG rate was strongly influenced by the local slip systems ahead of the crack tip. Significant anisotropy in KIC, a result of the crack deflection by the NPR/matrix interfaces, was observed. The mesostructure induced toughening mechanism improves the fracture toughness of the resultant alloy despite its brittle failure response. The potential of in-situ alloying to induce toughening through the mesostructure control was discussed.
License type:
Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
Funding Info:
This research / project is supported by the Agency for Science, Technology and Research - Structural Metal Alloys Programme
Grant Reference no. : A18B1b0061