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Assessing the fracture toughness in Tungsten-based nanocomposites: A micro-mechanical approach.

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Title: Assessing the fracture toughness in Tungsten-based nanocomposites: A micro-mechanical approach.
Authors: Schmuck, K.1 (AUTHOR), Burtscher, M.1 (AUTHOR), Alfreider, M.1 (AUTHOR), Kiener, D.1 (AUTHOR) daniel.kiener@unileoben.ac.at
Source: Materials & Design. Nov2024, Vol. 247, pN.PAG-N.PAG. 1p.
Subjects: Young's modulus, Fracture toughness, Mechanical alloying, Zinc alloys, Copper
Abstract: [Display omitted] • Grain-size tailoring of WCu and W-α-brass in the nc-regime by high-pressure torsion. • Young's modulus variation due to significant change of grain-boundary volume. • Assessing fracture characteristics by in-situ micro cantilever bending beams. • Improve of mechanical properties by alloying the copper phase with 10 wt.% zinc. Nanocrystalline tungsten-copper composites can favorably combine the outstanding material properties of both elements. This work investigates tungsten-copper composites fabricated from elemental powders with 80 wt.% tungsten and either copper or α -brass containing 20 wt.% zinc, respectively. Moreover, high-pressure torsion is used to compact the powders, strengthen the resulting composite by grain refinement, and tailor the grain-size in the nanocrystalline regime by varying the deformation temperature between RT, 400°C and 550°C, resulting in grain-sizes of 9 nm 14 nm and 28 nm, respectively. Hardness measurements revealed a transition from normal to inverse Hall-Petch behavior for grain-sizes below 11 nm. To examine the fracture properties, micro-cantilever bending beams with a cross-section of 10x10 µm2 were fabricated. Evaluation of these experiments indicated a fracture toughness of 3 MPa m . The slight decrease of fracture toughness between a grain-size of 9 nm to 14 nm indicates a reduction of the grain boundary cohesion strength. The grain-size increase to 28 nm reversed the trend in fracture toughness and raised it to 3.4 MPa m , which points to activating additional deformation mechanisms, such as dislocation-accumulation and twinning. Additionally, alloying with zinc raised the composites strength and retained the composites fracture toughness, benefiting the damage tolerance. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:[Display omitted] • Grain-size tailoring of WCu and W-α-brass in the nc-regime by high-pressure torsion. • Young's modulus variation due to significant change of grain-boundary volume. • Assessing fracture characteristics by in-situ micro cantilever bending beams. • Improve of mechanical properties by alloying the copper phase with 10 wt.% zinc. Nanocrystalline tungsten-copper composites can favorably combine the outstanding material properties of both elements. This work investigates tungsten-copper composites fabricated from elemental powders with 80 wt.% tungsten and either copper or α -brass containing 20 wt.% zinc, respectively. Moreover, high-pressure torsion is used to compact the powders, strengthen the resulting composite by grain refinement, and tailor the grain-size in the nanocrystalline regime by varying the deformation temperature between RT, 400°C and 550°C, resulting in grain-sizes of 9 nm 14 nm and 28 nm, respectively. Hardness measurements revealed a transition from normal to inverse Hall-Petch behavior for grain-sizes below 11 nm. To examine the fracture properties, micro-cantilever bending beams with a cross-section of 10x10 µm2 were fabricated. Evaluation of these experiments indicated a fracture toughness of 3 MPa m . The slight decrease of fracture toughness between a grain-size of 9 nm to 14 nm indicates a reduction of the grain boundary cohesion strength. The grain-size increase to 28 nm reversed the trend in fracture toughness and raised it to 3.4 MPa m , which points to activating additional deformation mechanisms, such as dislocation-accumulation and twinning. Additionally, alloying with zinc raised the composites strength and retained the composites fracture toughness, benefiting the damage tolerance. [ABSTRACT FROM AUTHOR]
ISSN:02641275
DOI:10.1016/j.matdes.2024.113433