Nanoengineering applied to tungsten

We have investigated the microstructure and mechanical properties of fully dense tungsten with ultrafinegrained (UFG) and nanocrystalline (NC) microstructure. The UFG/NC tungsten was processed by severe plastic deformation at low homologous temperatures (T/T_m). To obtain the UFG microstructure, a combination of equal channel angular pressing at relatively high temperatures followed by rolling at lower temperatures was employed, which resulted in an average grain size of ∼500 nm. To obtain the nanocrystalline microstructure (grain size ∼100 nm and below), high-pressure torsion was utilized. Our experimental results show that the UFG/NC microstructures not only significantly elevate the strength of tungsten, they also re-instate its ductility, decrease its strain rate sensitivity, and reduce its work hardening capability. These factors work together to greatly enhance the susceptibility of tungsten to adiabatic shear localization under uni-axial dynamic loading.