Developing Nanostructures and Enhanced Properties in Heavy W Alloy through SPD Processing

摘要

The ways of fulfillment of severe plastic deformation (SPD) processes by equal channel angular (ECA) pressing of hard-to-deform low-ductility materials, namely W of the commercial purity and W alloy of W-Ni-Fe system were developed. To obtain ultra-fine grained (UFG) structures in these materials the dies for high-cycle ECA pressing were fabricated. For the first time ECA pressing was implemented and the optimal regimes of obtaining of bulk commercially pure (CP) W ingots with UFG structure were established. First experiments of ECA pressing of heavy alloy W-4.9%Ni-2.1% Fe were conducted. TEM and X-ray investigations of the SPD-processed CP W showed that the refinement of the structure up to a mean grain size less than 1 micrometers takes place during ECA pressing. The grains have mainly high angle boundaries that results in enhanced mechanical properties. Hardening of the investigated material during SPD was indicated by microhardness measurements. To attain further progress in refinement of W-alloy structure by ECA pressing and due to this increase their mechanical properties new ways were suggested.