Development and characterization of Ti-6Al-4V/C103 functionally graded material using LP-DED

This paper explores the fabrication and characterization of functionally graded Ti-6Al-4V–C103 thin wall specimens produced using Laser Powder Directed Energy Deposition (LP-DED). Thin walls were successfully manufactured with three distinct transition steps: 100 wt%, 50 wt%, and 25 wt%. Geometrical analysis demonstrated printing fidelity and consistent build quality across experimental setups. EDS validated the compositional gradients along the build direction, while discrepancies between expected and measured compositions were attributed to the presence of unmelted C103 particles. Quantitative analysis revealed that the area fraction of unmelted particles increased with higher C103 content. SEM and EBSD analyses revealed microstructural evolution from coarse columnar to finer equiaxed grains with increasing C103. Dendritic width analysis further revealed that increasing C103 content led to the refinement of Ti-rich regions and the coarsening of Nb-rich regions within the graded deposition zones. Microhardness measurements exhibited a nonlinear trend with composition, peaking at 425 HV for 25 wt% C103 potentially due to possible presence of ω-phase in this graded region, while further addition of C103 lead to a decrease on the overall microhardness.