In this connection, in the frame of the third period of the present project there have been conducted experimental investigations, aimed at equal channel angular pressing (ECAP) optimization of the investigated W and the 90W-8Ni-2Fe alloy. The problem of this task consists in enhancing workability of these hard-to-deform materials and achieving large strains, The influence of the accumulated strain degree the thickness of protection casing, the rate and strain temperatures on grain size and homogeneity of the obtained structure have been investigated as parameters, determining ECAP results. ECAP has been realized on route C, which turns out to be the most effective route for the given case, as it has been found out at first stages of the project.

The present report presents the results of an experimental investigation and numerical simulation of the process of equal-channel angular pressing with a backpressure equal to 2.4 sigma(sub s) which have allowed to increase the accumulated strain rate up to e=7, what allows to obtain ultrafine-grained structure with a grain size less than 0.5 micrometers. Note should be made that in that case the punch loading was close to its calculated value, which is in conformity with the strength characteristics of the material and the die-set design. With the purpose of studying the influence of initial state on the ultrafine-grained structure formation there were carried out comparative investigations of the behavior of single- and polycrystalline tungsten during severe plastic deformation process. A possibility of reducing the severe plastic deformation temperature when using special sheathing for tungsten billets is being investigated. There were started investigations of the microstructure refinement of the W-2%Re alloy with enhanced strength and ductility at severe plastic deformation.

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.

The results of a state-of-the-art survey covering tungsten and ten of its alloys are presented. All data are given in tabular and graphical form covering some of the more important physical, mechanical, and metallurgical properties for each material. References are given at the conclusion of each material section.

This definitive work is the most uptodate compendium on tungsten in over twenty years. Wolf-Dieter Schubert's scientific career and extensive research activities combined with Erik Lassner's long-term industrial and development knowledge make this an essential resource on the current status of tungsten science and technology. Consolidating new knowledge previously presented at seminars or in the technical press, Tungsten is a significant contribution to the broader acceptance of the most recent innovations in the field. The text is enhanced by over 300 illustrations.