Behavior of tungsten fiber-reinforced tungsten based on single fiber push-out study

Jasper, B.; Schoenen, S.; Du, Jun; Hoeschen, T.; Koch, F.; Linsmeier, Ch.; Neu, R.; Riesch, J.; Terra, A.; Coenen, J. W.

doi:10.1016/j.nme.2016.04.010

Cited by 28 publications

(22 citation statements)

References 21 publications

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“…Tungsten fiber-reinforced composites (Wf/W) are extensively investigated as a potential material for advanced plasma facing components [11]. This composite structure is obtained by embedding commercially available drawn tungsten wires in a tungsten matrix which is produced either by powder metallurgy [12] or by a chemical deposition process [13]. The advantage of Wf/W is in its pseudo ductile behavior and thereby increased toughness as a consequence of extrinsic toughening mechanism such as crack bridging by intact fibers, fiber pull-out, crack deflection and ductile deformation of fibers [14].…”

Section: Introductionmentioning

confidence: 99%

The effect of heat treatments on pure and potassium doped drawn tungsten wires: Part I - Microstructural characterization

Nikolić

Riesch

Pippan

2018

Materials Science and Engineering: A

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Advanced tungsten fibre-reinforced composites (Wf/W), showing pseudo ductile behaviour even at room temperature, are a promising option for future fusion reactors as the intrinsic brittleness of tungsten can be mitigated effectively. The drawn tungsten wires used as reinforcements are the key component of the composites, thus their mechanical properties and thermal stability define the allowed operation / fabrication temperature of the composite material itself. In this work, a comprehensive characterization of the pure and potassium doped tungsten wires was performed, focusing on the influence of various heat treatments on different microstructural features (nature of grain boundaries, grain shape and size, texture analyses) and mechanical properties. Annealing in the temperature range from 900-1600°C enables the investigation of the microstructural stability of the two materials and arising annealing phenomenarecovery, recrystallization and grain growth. The results demonstrate that the pure tungsten recrystallizes fully in the temperature range 1300-1500°C accompanied with tremendous coarsening and a complete loss of the initial fibrous, elongated grain structure. In contrast to this, potassium doped wire shows superior high temperature properties, where performed heat treatments cause only milder microstructural changes, consequently suppressing recrystallization and grain growth to temperatures well above the investigated ones. Furthermore, hardness measurements and observed softening complement the discussion of the grain morphology evolution.

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Section: Introductionmentioning

confidence: 99%

The effect of heat treatments on pure and potassium doped drawn tungsten wires: Part I - Microstructural characterization

Nikolić

Riesch

Pippan

2018

Materials Science and Engineering: A

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“…It is assumed that it is caused by geometrical irregularities of the fibers [14]. However, the experimentally derived force-displacement curves of push-out tests of Du [14] and Jasper [15] lead to the conclusion that an interface pressure is somehow present during the frictional phase of the experiments after the completion of interface debonding.…”

Section: Interface Properties Of W F /Wmentioning

confidence: 99%

“…The shear lag model, which is commonly used to describe the push-out force during the frictional phase after the completion of debonding, is only valid for small relative displacements between fiber and matrix [17]. The well established finite element method (FEM) was applied to create a deeper understanding of the mechanisms that are acting during the different phases of a push-out test, accompanying the experimental work of Jasper [15].…”

Section: Interface Properties Of W F /Wmentioning

confidence: 99%

Insight into single-fiber push-out test of tungsten fiber-reinforced tungsten

Schönen

Jasper

Coenen

et al. 2018

Composite Interfaces

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To overcome the intrinsic brittleness of tungsten (W), a tungsten fiber-reinforced tungsten-composite material (W f /W) is a possible solution. The introduction of energy dissipation mechanisms like fiber bridging or fiber pull-out by means of an engineered interface between fiber and matrix mitigate the brittleness of tungsten and lead to a pseudo-ductile material behaviour. The push-out test of single-fiber samples is an experimental method to investigate the properties of the interface between fiber and matrix of composite materials. It is widely used for the investigation of ceramic composites. This method was also used to investigate the debonding and frictional properties of the Er2O3 interface region between fiber and matrix of W f /W single-fiber samples made by CVD-and HIP-processes. In this article finite element calculations are used to get a better understanding of the processes acting in the interface during a push-out test of W f /W. A detailed overview of the debonding progress and of the corresponding stress states of the interface during the different stages of the test is presented. In addition the sensitivity of the push-out behaviour regarding the different interface properties and the plastic flow curve of the tungsten fiber are investigated.

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“…The proof of extrinsic toughening in such a composite system has been shown in the past years at the Max-Planck-Institute for Plasma Physics, Garching (IPP) [15]. W f /W composites consist of tungsten fibers made of commercially drawn tungsten wire embedded in a tungsten matrix produced either by a chemical process [16] or by powder metallurgy [17].…”

Section: Introductionmentioning

confidence: 99%

Plastic deformation of recrystallized tungsten-potassium wires: Constitutive deformation law in the temperature range 22–600 °C

Terentyev

Riesch

Lebediev

et al. 2018

International Journal of Refractory Metals and Hard Materials

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Recent efforts dedicated to the mitigation of tungsten (W) brittleness have demonstrated that tungsten fiber-reinforced composites acquire extrinsic toughening even at room temperature, which is due to the outstanding strength of W wires. However, high temperature operation/fabrication of the fiber-reinforced composite might result in the degradation of the mechanical properties of W wires. To address this, we investigate mechanical and microstructural properties of potassium-doped tungsten wires, being heat treated at 2300°C and tested in temperature range 22-600°C. Based on the microscopic analysis, the engineering deformation curves are converted into actual stress-strain dataset, accounting for the local necking. The analysis demonstrates that local strain in the necking region can reach up to 50% and the total elongation monotonically increases with temperature, while the ultimate tensile strength goes down. Preliminary transmission electron microscopy analysis using FIB-cut lamella from the necking region revealed the presence of curved dislocation lines in the sample tested at 300C, proving that plastic deformation occurred by dislocation glide.

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Behavior of tungsten fiber-reinforced tungsten based on single fiber push-out study

Cited by 28 publications

References 21 publications

The effect of heat treatments on pure and potassium doped drawn tungsten wires: Part I - Microstructural characterization

The effect of heat treatments on pure and potassium doped drawn tungsten wires: Part I - Microstructural characterization

Insight into single-fiber push-out test of tungsten fiber-reinforced tungsten

Plastic deformation of recrystallized tungsten-potassium wires: Constitutive deformation law in the temperature range 22–600 °C

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Behavior of tungsten fiber-reinforced tungsten based on single fiber push-out study

Cited by 28 publications

References 21 publications

The effect of heat treatments on pure and potassium doped drawn tungsten wires: Part I - Microstructural characterization

The effect of heat treatments on pure and potassium doped drawn tungsten wires: Part I - Microstructural characterization

Insight into single-fiber push-out test of tungsten fiber-reinforced tungsten

Plastic deformation of recrystallized tungsten-potassium wires: Constitutive deformation law in the temperature range 22–600 °C

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Plastic deformation of recrystallized tungsten-potassium wires: Constitutive deformation law in the temperature range 22–600 °C