In future fusion reactors, tungsten is considered as the main candidate material for plasma-facing components. However, the intrinsic brittleness of tungsten is of great concern during operation. To overcome this drawback, tungsten fiber-reinforced tungsten composites (Wf/W) are being 2 developed relying on extrinsic toughening principles. Tungsten (W) fibers with extremely high tensile strength and ductility are used to reinforce a tungsten matrix. In this work, field assisted sintering technology (FAST) is used to produce Wf/W material. Mechanical characterizations including Charpy impact and 3-point bending tests are performed. Based on the 3-point bending test results, the Wf/W materials can facilitate a promising pseudoductile behavior even at room temperature, similar to fiber reinforced ceramic composites. Fracture energy density and fracture toughness together with the crack-resistance curves (R-curves) are measured. Compared to conventional pure tungsten, Wf/W shows significant improvement in fracture toughness.

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As a candidate material for plasma facing material in future fusion reactor, tungsten (W) fiber reinforced tungsten (Wf/W) composite has been recently developed. The crack resistance of Wf/W is proven to be significantly higher compared to normal tungsten. However, the W-fibers used always become embrittlement during the powder metallurgy (PM) processes. In order to understand this significant issue, in this work, a series of Wf/W composites have been prepared.Microstructural and mechanical studies revealed that microstructural and mechanical studies revealed that the nanosized carbides in the grains and the carbide-layer on the grain boundaries are formed during PM processes. Especially, the carbide-layer on the grain boundaries can cause the brittle fracture of those W-fibers affected. Meanwhile, W-foil protection of the green body during the sintering process can reduce the carbon contamination effect and allows to preserve the ductility of the tungsten fibers used