Mechanical Behavior of Neutron Irradiated Ta-W Alloys
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Ghanbari, Zahra [Sandia National Laboratories (SNL↗
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Additive Manufacturing of Ta-W Alloys: A Gradient Approach to Microstructure and Cracking Behavior
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Materials science↗
Quasi-static to Dynamic Mechanical Response and Microstructure Development of Tantalum-Tungsten Alloys
Lawrence Livermore National Laboratory (LLNL) is interested the quasi-static to dynamic mechanical response and microstructure evolution of tantalum-tungsten (Ta-W) alloys (Ta-2.5W, Ta-5W, and Ta-10W, wt.%) made by conventional wrought processing and additive manufacturing (AM). This work scope was performed at the Colorado School of Mines (Mines) and included quasi-static (e.g., 10 -3 s -1 ) mechanical testing in tension and compression, along with selected high strain rate (Kolsky) pressure bar testing in compression (e.g., 10 3 s -1 ), with and without temperature variations in some instances. Complementary microstructure characterization was performed on undeformed and deformed samples to understand the role of processing on microstructural evolution and the deformation mechanisms that impact the mechanical response with variations in strain rate, temperature, and strain state (e.g., tension versus compression in selected examples). The wrought material provided by LLNL from Viridis Materials was found to have unrecrystallized regions within the microstructure, which led to unexpected results relative to previously reported properties for Ta-W. The AM Ta-2.5W (wt.%) material provided by LLNL was found to have higher compressive strength than wrought Ta-2.5W (wt.%), which is hypothesized to be due to differences in the crystallographic texture between the two materials. This project partially supported several postdocs and graduate students at Mines.
36 MATERIALS SCIENCE↗
Influence of rolling reduction and annealing on recrystallization and grain structure in Ta-2.5W alloys
The microstructural evolution of wrought Tantalum - 2.5 wt% Tungsten (Ta-2.5W) alloys during thermomechanical processing is critical for optimizing their mechanical reliability in demanding applications such as aerospace, chemical processing, and nuclear technology. Despite the widespread use of Ta-W alloys, a comprehensive understanding of how rolling reduction, annealing temperature, and elemental inhomogeneity interact to determine recrystallization behavior and grain refinement remains incomplete. Here, in this study, we systematically investigate the effects of cold rolling and subsequent annealing on the microstructure of Ta-2.5W, with particular attention to grain orientation, stored energy, and elemental banding. Our results demonstrate that higher rolling reduction rates lower the onset and completion temperatures for recrystallization, resulting in finer and more homogeneous grain structures. Electron backscatter diffraction (EBSD) analysis reveals that grains with a 〈111〉 parallel to the plate normal possess higher stored energy and nucleate recrystallization more readily than grains with a 〈001〉 parallel to the plate normal. Elemental mapping shows that tungsten inhomogeneity leads to localized bands of accelerated recrystallization and hardness variation. These findings provide new insights into the mechanisms of microstructure refinement in Ta-2.5W alloys, offering guidance for tailoring processing routes to achieve superior performance in demanding engineering environments.
Annealing↗
Quasi-static to Dynamic Response and Microstructure Development of Tantalum-Tungsten Alloys
Lawrence Livermore National Laboratory (LLNL) has a need to understand the quasi-static to dynamic mechanical response and microstructure evolution of tantalum-tungsten (Ta-W) alloys made by conventional wrought processing and additive manufacturing (AM). This two-year work scope will be performed at the Colorado School of Mines (Mines) and will include quasi-static (e.g., 10 -3 s -1 ) mechanical testing in tension and compression, along with high strain rate (Kolsky) pressure bar testing in tension and compression (e.g., 10 3 s -1 ), without and with temperature variations. Gas gun experiments at higher strain rates (e.g., over 10 3 s -1 ) will also be pursued. Complementary microstructure characterization will be performed on undeformed and deformed samples to fundamentally understand the role of processing on the microstructure characteristics and resulting deformation mechanisms that dictate the mechanical response of these alloys with variations in strain rate, temperature, and strain state. Alloys of interest will be Ta-based, containing up to 10 wt.% W. LLNL will supply initial wrought-processed material for sample machining. LLNL will also supply samples built by AM during the project for testing. Arc melting and casting may also be performed at Mines to produce small quantities of different alloys for machining and exploratory testing on an as-needed basis. This project will support multiple postdocs and graduate students at Mines, training them with the knowledge, skills, and abilities needed to study materials under extreme conditions of interest to the National Nuclear Security Agency.
36 MATERIALS SCIENCE↗
Materials Data on TaW by Materials Project
TaW crystallizes in the orthorhombic Cmmm space group. The structure is two-dimensional and consists of two TaW sheets oriented in the (0, 1, 0) direction. Ta is bonded in a 4-coordinate geometry to four equivalent W atoms. All Ta–W bond lengths are 2.80 Å. W is bonded in a 4-coordinate geometry to four equivalent Ta atoms.
36 MATERIALS SCIENCE↗
Materials Data on Ta3W by Materials Project
Ta3W is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent Ta sites. In the first Ta site, Ta is bonded to four equivalent Ta and four equivalent W atoms to form a mixture of distorted edge, corner, and face-sharing TaTa4W4 tetrahedra. All Ta–Ta bond lengths are 2.84 Å. All Ta–W bond lengths are 2.84 Å. In the second Ta site, Ta is bonded in a 8-coordinate geometry to eight equivalent Ta and six equivalent W atoms. All Ta–W bond lengths are 3.28 Å. W is bonded in a distorted body-centered cubic geometry to fourteen Ta atoms.
36 MATERIALS SCIENCE↗