Tungsten (W) is the metal with the highest melting point among all pure metals (Tm = 3422°C) and would therefore be an excellent fit for challenging high temperature applications. However, its low-temperature brittleness impedes its use as a structural material.
The situation appears different for heavily cold rolled, ultrafine-grained (UFG) tungsten sheets. These sheets possess room-temperature tensile ductility combined with a low brittle-to-ductile transition temperature and a high toughness.
Our material development strategy makes use of these UFG W sheets and contains the following sub-projects:
(i) the rolling of the W sheets at very high degrees of deformation and very low homologous temperatures,
(ii) the stabilization of the UGF microstructure by doping with potassium (K),
(iii) the diffusion bonding of the thin, K-doped W sheets into a UFG bulk material.
In this contribution we give an overview of the progress in the three sub-projects introduced above. We address fundamental question on plastic deformation, fracture, and recrystallization mechanisms in heavily cold rolled tungsten sheets and present the fabrication of a 100 % monolithic, UFG, ductile tungsten pipe for structural applications.