Activated sintering of tungsten alloys through conventional and spark plasma sintering process

Senthilnathan, N.; Annamalai, A. Raja; Venkatachalam, G.

doi:10.1080/10426914.2017.1328109

Cited by 24 publications

(7 citation statements)

References 26 publications

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“…The consolidation of nanocrystalline powders into bulk materials has relied extensively on field-assisted sintering technology (FAST) to circumvent the coarsening kinetics by rapidly heating a powder charge using an electric current passed simultaneously through a graphite die and the powder during the simultaneous application of an external pressure [37,38]. Through closed-loop feedback control, the current is manipulated to tailor the temperature profile in the powder (though gradients are expected that depend on the thermal and electrical conductivity of the powder charge [39]), which, when combined with the applied force, promote rapid densification of the powder feedstock into a bulk material over time that limits the degree of coarsening experienced by the microstructure [40].…”

Section: Introductionmentioning

confidence: 99%

“…Given the intrinsic thermal instabilities of nanocrystalline W combined with recrystallization temperatures ranging from 1100-1300 • C (depending on the W grade) [45][46][47][48], FAST is even limited in its ability to retain nano grain sizes in W despite the short sintering times [49][50][51][52]. The addition of second phase components such as WC, NiFe, and NiCu have driven the lower bound of this temperature range down to ~1200 • C for full density compacts, albeit often containing a second lower temperature phase [37,44]. Nanostructure stabilization via grain boundary doping as demonstrated in the W-20 at.% Ti alloy powder discussed above opens up the possibility of producing bulk nanocrystalline alloys from nano-engineered powders.…”

Section: Introductionmentioning

confidence: 99%

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Microstructural Transitions during Powder Metallurgical Processing of Solute Stabilized Nanostructured Tungsten Alloys

Olynik

Cheng

Sprouster

et al. 2022

Metals

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Exploiting grain boundary engineering in the design of alloys for extreme environments provides a promising pathway for enhancing performance relative to coarse-grained counterparts. Due to its attractive properties as a plasma facing material for fusion devices, tungsten presents an opportunity to exploit this approach in addressing the significant materials challenges imposed by the fusion environment. Here, we employ a ternary alloy design approach for stabilizing W against recrystallization and grain growth while simultaneously enhancing its manufacturability through powder metallurgical processing. Mechanical alloying and grain refinement in W-10 at.% Ti-(10,20) at.% Cr alloys are accomplished through high-energy ball milling with transitions in the microstructure mapped as a function of milling time. We demonstrate the multi-modal nature of the resulting nanocrystalline grain structure and its stability up to 1300 °C with the coarser grain size population correlated to transitions in crystallographic texture that result from the preferred slip systems in BCC W. Field-assisted sintering is employed to consolidate the alloy powders into bulk samples, which, due to the deliberately designed compositional features, are shown to retain ultrafine grain structures despite the presence of minor carbides formed during sintering due to carbon impurities in the ball-milled powders.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Microstructural Transitions during Powder Metallurgical Processing of Solute Stabilized Nanostructured Tungsten Alloys

Olynik

Cheng

Sprouster

et al. 2022

Metals

View full text Add to dashboard Cite

show abstract

“…At the same time, the addition of 10 vol.% of WC resulted in 99% density and 3μm grains at 1700 °C, with a pressure of 85 MPa for 5 min. Further temperature and time lowering were achieved within the SPS process by Senthilnathan et al [ 13 ], leading to W+1%Ni being consolidated to 90% density at 1200 °C and 30 MPa for 3 min. The material, however, contained Ni, which was shown to accelerate the tungsten recrystallization [ 8 ].…”

Section: Introductionmentioning

confidence: 99%

High Densification of Tungsten via Hot Pressing at 1300 °C in Carbon Presence

Popov

Vishnyakov

2022

Materials

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A reactive sintering technique with a small addition of carbon (up to 1.9 wt.%) has been used for tungsten powder consolidation. The process allowed procurement of the nonporous and fully densified material at 1300 °C and 30 MPa in 12 min. The SEM and EDX analysis showed that the milling of 5 μm tungsten powder with 0.6, 1.3, and 1.9 wt.% of carbon in a planetary mill led to the formation of the nanostructured mix, which appears to be W-C nanopowder surrounding tungsten grains. X-Ray Diffractometry data indicated tungsten hemicarbide (W2C) nucleation during the hot pressing of the milled powders. The exothermic reaction 2W + C → W2C occurs during the sintering process and promotes charge densification. The Vickers hardness and indentation toughness of W-1.3 wt.%C composition reached 5.7 GPa and 12.6 MPa∙m1/2, respectively. High toughness and high material densification allow proposing the W-WC2 for use as a plasma-facing material in fusion applications.

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“…The high melting point of tungsten makes it a premium element in plasma-facing components in reactors [ 2 , 3 , 4 , 5 ], electrical contacts [ 6 ], electron emitters, welding electrodes, sputtering targets, and heat sinks [ 7 ]. The other major feature of tungsten is its high density (19.3 g/cm 3 ), which is a needed property in radiation shielding applications [ 8 , 9 ]. One major drawback of tungsten is its property of brittleness below the ductile-to-brittle transition temperature.…”

Section: Introductionmentioning

confidence: 99%

Effect of Rare Earth Metals (Y, La) and Refractory Metals (Mo, Ta, Re) to Improve the Mechanical Properties of W–Ni–Fe Alloy—A Review

et al. 2021

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Tungsten heavy alloys are two-phase metal matrix composites that include W–Ni–Fe and W–Ni–Cu. The significant feature of these alloys is their ability to acquire both strength and ductility. In order to improve the mechanical properties of the basic alloy and to limit or avoid the need for post-processing techniques, other elements are doped with the alloy and performance studies are carried out. This work focuses on the developments through the years in improving the performance of the classical tungsten heavy alloy of W–Ni–Fe through doping of other elements. The influence of the percentage addition of rare earth elements of yttrium, lanthanum, and their oxides and refractory metals such as rhenium, tantalum, and molybdenum on the mechanical properties of the heavy alloy is critically analyzed. Based on the microstructural and property evaluation, the effects of adding the elements at various proportions are discussed. The addition of molybdenum and rhenium to the heavy alloy gives good strength and ductility. The oxides of yttrium, when added in a small quantity, help to reduce the tungsten’s grain size and obtain good tensile and compressive strengths at high temperatures.

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Activated sintering of tungsten alloys through conventional and spark plasma sintering process

Cited by 24 publications

References 26 publications

Microstructural Transitions during Powder Metallurgical Processing of Solute Stabilized Nanostructured Tungsten Alloys

Microstructural Transitions during Powder Metallurgical Processing of Solute Stabilized Nanostructured Tungsten Alloys

High Densification of Tungsten via Hot Pressing at 1300 °C in Carbon Presence

Effect of Rare Earth Metals (Y, La) and Refractory Metals (Mo, Ta, Re) to Improve the Mechanical Properties of W–Ni–Fe Alloy—A Review

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