Design of tungsten fiber-reinforced tungsten composites with porous matrix

Abstract

To overcome the brittleness of tungsten, tungsten fiber-reinforced tungsten composites (Wf/W) have been developed using an extrinsic toughening mechanism. In this work, a novel type of Wf/W with porous matrix produced by field assisted sintering technology (FAST) is studied. The material is optimized regarding mechanical behavior, standing on the adjusting of matrix porosity and fiber mass fraction. Two series of samples with different matrix density and fiber mass fraction are prepared. Based on the mechanical testing, porous matrix Wf/W can represent a promising pseudo ductile behavior. Relatively lower matrix density is helpful to avoid a sudden load-drop during crack opening. The different fracture behavior is attributed to the different fiber/matrix interface bonding condition. By increasing fiber mass fraction from 20% to 50%, porous matrix Wf/W can facilitate improved mechanical properties regarding fracture toughness and strength. However, by further increasing the fiber mass fraction from 50% to 60%, a deterioration of mechanical properties is observed. The high porosity of porous matrix Wf/W causes a degradation of the thermal conductivity compared to conventional bulk tungsten. No significant change regarding thermal expansion coefficient is observed when decreasing the matrix density.