Interfacial fracture behavior of tungsten wire/tungsten matrix composites with copper-coated interfaces

The potential application of tungsten as a structural material has been strongly restricted by inherent brittleness. The hitherto metallurgical efforts to improve tungsten toughness seem to be still less matured. The authors have been exploring a novel toughening technique based on reinforcement by tungsten wires. Toughness is supposed to be enhanced through the energy dissipation at the wire/matrix interfaces which is caused by the controlled crack deflection and friction. In this work, we focus on two kinds of copper coatings for interface engineering, namely, copper single-layer and copper/tungsten multi-layer. Single-filament composites were fabricated using magnetron sputtering and CVD process. The interfacial parameters were identified by means of fiber push-out test and microscopic fracture features were investigated. In this paper the results from the extensive push-out experiments are presented together with the fractographs. Finite element simulation was also carried out to estimate the plastic strain of the copper layer. Essential role of the significant plastic deformation in the overall failure behavior is highlighted.