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Materials Science in Additive Manufacturing L-PBF Ti-10Ta-2Nb-2Zr: Microstructure and Strength

the Ti-10Ta-2Nb-2Zr alloy. Table 3 summarizes the tensile transition from elastic to plastic deformation compared to
properties before and after heat treatment. the sharper yield point of the as-built condition, consistent
The heat treatment had a significant impact on the with the more homogeneous, recrystallized microstructure
mechanical properties of the Ti-10Ta-2Nb-2Zr alloy, with reduced internal stresses.
as previously presented in Section 3.4. Heat treatment 3.6. TPMS structures
resulted in a notable reduction in strength properties, with
yield strength decreasing from 551.8 ± 8.4 MPa to 452.3 Figure 10 presents experimental cylindrical specimens
± 14.7 MPa (approximately 18% reduction) and ultimate (6 mm diameter, 12 mm height) with different types of
tensile strength decreasing from 641.2 ± 5.7 MPa to 545.0 TPMS architectures fabricated using L-PBF with Ti-10Ta-
± 3.6 MPa (approximately 15% reduction). 2Nb-2Zr alloy. (A) Schwarz structure, (B) gyroid structure,
and (C) split structure. All samples are characterized
Heat treatment resulted in a notable reduction in by 50% volumetric porosity and 1.5 mm unit cell size.
strength properties, with yield strength decreasing by The manufacturing quality of all structures confirms
18.0% and ultimate tensile strength by 15.0%. This strength the technological capabilities of the L-PBF process for
reduction is directly attributable to the replacement of the reproducing complex biomimetic architectures.
fine martensitic structure with a coarser lamellar α + β
microstructure, which offers fewer barriers to dislocation 3.6.1. Compression mechanical properties
movement. The results of compressive testing of Ti-10Ta-2Nb-2Zr
Interestingly, the elastic modulus decreased slightly lattice structures (Table 5) report characteristic features
from 89.0 GPa to 86.0 GPa (−3.4%) after heat treatment. determined by their architecture and L-PBF process. The
This reduction, while modest, is beneficial for biomedical elastic modulus of all investigated lattice structures lies
applications as it brings the material’s stiffness closer to within a narrow range of 9.2 – 9.7 GPa, which represents
that of bone, potentially reducing stress-shielding effects approximately 18% of the solid material value (52.2 GPa).
in orthopedic implants. Such a significant reduction in stiffness is typical for
porous structures and is attributed to the decreased volume
The effect on ductility parameters was mixed:
elongation increased from 19.0% to 20.2% (+6.3%), fraction of material in the lattice.
indicating improved uniform deformation capacity, The yield strength of lattice structures varies depending
while reduction in area decreased from 58.0% to 45.8% on their topology: the Schwarz structure shows the highest
(−21.0%), suggesting a reduced localized necking values (207.9 MPa), followed by gyroid (198.4 MPa) and
ability. The greater variability in ductility measurements split (193.6 MPa). These differences may be associated with
after heat treatment (standard deviations of 3.6% for the specific stress distribution patterns in different lattice
elongation and 15.5% for reduction in area) indicates topologies under compression.
less consistent fracture behavior compared to the as-built Notably, the gyroid structure demonstrates the lowest
condition. scatter of experimental data among all investigated lattice
The stress-strain curves confirm the reduced strength types. The standard deviation is 2 – 3 times smaller
and slightly enhanced elongation after heat treatment compared to other structures (Figure 11). Such high
(Figure 8). The heat-treated sample exhibits a more gradual reproducibility of results is attributed to the geometric

A B C

Figure 10. As-built cylindrical specimens with different types of triply periodic minimal surface. (A) Schwarz; (B) Gyroid; (C) Split

Volume 4 Issue 3 (2025) 12 doi: 10.36922/MSAM025220044