Fiber Volume Fraction Influence on Randomly Distributed Short Fiber Tungsten Fiber‐Reinforced Tungsten Composites

Abstract

For future fusion reactors, tungsten (W) is currently the main candidate for the application as plasma‐facing material due to its several advanced properties. To overcome the brittleness of W, randomly distributed short W fiber‐reinforced W (Wf/W) composites have been developed using field‐assisted sintering technology (FAST). Herein, Wf/W materials with different fiber volume fraction (20–60%) are manufactured by FAST process to study the fiber volume fraction influence on the composite properties. Wf/W with ductile fibers and brittle fibers is produced using different tool setups during the production. Three‐point bending tests on prenotched samples, 4‐point bending tests, and tensile tests have been performed to determine the fracture behavior and flexural/tensile strength of the material. Wf/W materials with 30–40% fiber volume fraction exhibit a promising pseudoductile behavior, similar to fiber‐reinforced ceramic composites. However, Wf/W with 20% and >50% fiber volume fraction shows only a limited extrinsic toughening effect. In terms of flexural strength, with increasing fiber volume fraction, the tensile/flexural strength does not show a clear increasing tendency, or even lightly decreases.

Insight into the Microstructure and Tensile Behavior of the W–Cu Composite Reinforced with Tungsten Fibers and Particulates

“…The weak interface positions would form pre‐damage before the matrix failure under high loading. [ 25,26 ] In contrast, the composite here exhibited rather stable flow stress, indicating the proper coordination between the mechanisms, including frictional fiber pullout, elastic bridging between sintered W f and W p , interface debonding between W f and Cu, as well as the resulted crack deflection, as revealed by the fractography in Figure 2b–d. The complex competition among the abovementioned fracture modes is conducive to improving the stability of the energy dissipation behavior of the composite.…”

“…Very recently, it was reported that a sudden load drop and a followed load increase happened in the W f -reinforced W composites, [25] indicating the unstable crack propagation and rather low defect tolerance due to the crack bridging by fibers and the gradual interface debonding. It was also pointed out that the strength of the W f -reinforced W composites was dominated by the weak interface.…”

“…The weak interface positions would form pre-damage before the matrix failure under high loading. [25,26] In contrast, the composite here exhibited rather stable flow stress, indicating the proper coordination between the mechanisms, including frictional fiber pullout, elastic bridging between sintered W f and W p , interface debonding between W f and Cu, as well as the resulted crack deflection, as revealed by the fractography in Apart from the abovementioned experimental analysis, a 3D model of the fabricated tungsten-fiber-reinforced W-Cu composite was established based on the real size of the processed tensile specimen. In view of close meshing densities between the fiber and the surrounding matrix, as well as an efficient calculation, each dimension of the matrix part was shrunk to be half of the real value, whereas the inserted fiber was kept its real size to evaluate its role more precisely, as shown in Figure 3a.…”

Fusion Materials Development at Forschungszentrum Jülich

“…[111][112][113][114][115] In the following, a short overview on the basic mechanisms and achievements will be given based on the PM production route initially developed at Forschungszentrum Jülich GmbH. [110,111,[116][117][118][119] Typical samples of CVD and PM W f /W are shown in Figure 10 where usual sizes are in the range of 40 mm  40 mm  5 mm or slightly larger for the CVD route.…”

“…Yttrium is an ideal candidate as the interface material for the W f /W composite due to its several advanced properties: good thermal and chemical stability, high mechanical strength, and hardness. [104,116] Studies to understand the pull-out of fibers include modeling. [130] For the developed PM production of W f /W, the homogenous introduction of powder between the fibers is required for good material properties; therefore, short fibers are used in contrast to, Figure 5.…”