The recrystallization of commercially pure and doped tungsten wire drawn to high strain

Snow, David B.

doi:10.1007/bf02658299

Cited by 38 publications

(16 citation statements)

References 6 publications

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“…Furthermore, tremendous softening is observed with a reduction in hardness by more than 50% of initial value. The outlined results are in agreement with the previous studies of annealing properties of pure tungsten wires [38] as well as with the typically reported recrystallization temperature of tungsten (1300-1500°C) [39][40][41]. Nevertheless, the results are not in (complete) correlation with conclusions made by Zhao [28] where it was deduced that the wire fully recrystallizes already after annealing for 3h at 1000°C.…”

Section: Discussionsupporting

confidence: 89%

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: Discussionsupporting

confidence: 89%

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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“…This unique microstructural feature is related to the tendency of grains to deform by plane strain elongation [35] and in such a way they become shaped like ribbons curled around the wire axis. Such an appearance is typically seen in heavily deformed tungsten wire and has been reported by other researchers [36,37].…”

Section: Microstructuresupporting

confidence: 80%

The effect of heat treatments on pure and potassium doped drawn tungsten wires: Part II – Fracture properties

Nikolić

Riesch

Pfeifenberger

et al. 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, the room temperature fracture behaviour of the pure and potassium doped tungsten wires was investigated, focusing on the evolution of the fracture micromechanisms in respect to annealing. Single-edge-notched specimens were used, with the crack growth direction perpendicular to the drawing axis of the wire. The occurrence of either a brittle or a ductile response in the as-received state of both materials is a strong indication that the ductile-to-brittle transition temperature is about room temperature. Pure, annealed tungsten wire experiences a tremendous deterioration of the fracture toughness with a very prominent transition of the failure mode. The observed embrittlement by annealing can be related to the loss of the fibrous, elongated microstructure. In contrast to this, the results of the annealed, doped wire demonstrate that the microstructural stability and preservation of the initial, beneficial grain structure is directly reflected in the crack resistance of the material. Predominately ductile behaviour, with characteristic knife-edge necking, is seen even after annealing at 1600 °C.

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“…The strain to failure in wires C and D decreases to low values after annealing at 2000 Κ and at 2200 K, resp., which clearly corresponds to the brittleness due to the onset of the exaggerated grain growth (Fig. (Let us mention that the term recrystallization refers in this context to exaggerated grain growth [1].) 2.).…”

Section: Torsion Test On Wiresmentioning

confidence: 99%

“…Doping can certainly have a large effect on the recrystallization [1], and it is well known that deformation by swaging, wire drawing [2] and coiling [3] can also influence the temperature of recrystallization. Doping can certainly have a large effect on the recrystallization [1], and it is well known that deformation by swaging, wire drawing [2] and coiling [3] can also influence the temperature of recrystallization.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Process Annealing on the Recrystallization of Lamp Grade Tungsten

Nagy¹,

Uray²

1994

High Temperature Materials and Processes

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The effect of process annealing was studied on K-Al-Si doped tungsten wires drawn from a diameter of 0.39 mm to 0.125 mm according to the same drawing schedule, but wire A undergoing no process annealing, wire Β process annealed at 0.39 mm, wire C at 0.18 mm and wire D both at 0.39 mm and at 0.18 mm. The exaggerated grain growth started in wires A and Β at 2600 K, while in wires C and D it started already at about 2200 K. The coiling decreased these temperatures to about 2000 Κ or 1800 K, respectively. The changes in the microstructure have been followed up by scanning metallography and by the measurement of the excess electrical resistivity. (Upon microstructural coarsening the excess resistivity is proportional to the grain boundary area per unit volume.) Torsion tests were also made to reveal the possible brittleness after annealing at temperatures below the range of the exaggerated grain growth.

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The recrystallization of commercially pure and doped tungsten wire drawn to high strain

Cited by 38 publications

References 6 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

The effect of heat treatments on pure and potassium doped drawn tungsten wires: Part II – Fracture properties

The Effect of Process Annealing on the Recrystallization of Lamp Grade Tungsten

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