V. P. Pilyugin, T. M. Gapontseva, T. P. Tolmachev, T. I. Chashchukhina, L. M. Voronova, M. V. Degtyarev

EFFECT OF SEVERE DEFORMATION ON THE STRUCTURE, FRACTURE PATTERN AND MECHANICAL PROPERTIES OF REFRACTORY METALS

High-pressure torsion is a method enabling one to obtain high strains without destroying the material being processed and to form the submicro- and nanocrystalline states in it. In this paper, this technique serves to process some brittle refractory metals. Particularly, the effect of pressure on the plasticity of brittle refractory metals strained by high pressure torsion using Bridgman anvils is studied. Namely, the critical pressure required for the realization of severe plastic deformation of refractory metals without destroying it by high pressure torsion is established. This value of the deformation pressure is estimated as 0.05 of the bulk modulus or 0.015 of the shear modulus of each metal. It has been established that the structural transformations of brittle metals caused by high pressure torsion forming the submicro- and nanocrystalline states have a significant effect on the mechanical properties of the metals as leading to significant work hardening. Moreover, with increasing strain (the number of anvil rotations), the mechanism of the fracture of the samples changes from cleavage to quasi-ductile one on the boundaries of the crystallites.

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