FEATURES OF BCC-METALS (V,Nb,V-Zr-C) STRUCTURE FORMATION AT COLD AND LOW TEMPERATURE DEFORMATIONS UNDER PRESSURE

Tatiana M. Teterina ,  V. P. Pilyugin 

Russian Academy of Sciences, Ural Division, Institute of Metal Physics, 18 S.Kovalevskaya str., GSP-170, Ekaterinburg 620219, Russian Federation

Abstract

The submicro- and nanocrystal condition of metals causes a great interest because of its special physico-mechanical properties. We investigated microstructure of deformed samples BCC of metals and alloys (monocrystalline Nb - 99.98 per cent, V - 99.92 per cent, macrocrystalline alloy V-Zr-C). Influence of deformation on hardening of V at 80K and 300K and Nb at 300K was studied.

Samples were deformed shear under pressure upon Bridgman anvils. Pressure at deformation was changed from 6 up to 12 GPa. Working temperatures were 300K and 80K. Structures of the deformed samples were studied with the help of the electronic microscopy method.

The sequence of structure changes from initial through increase of dislocation density to cellular-dislocation structure and transformations of last to nanocrystalline grain (NC) structure was revealed. NC structure of V and Nb is formed at achievement of true deformation e=7 and more with the most probable nanocrystalline grain of 20 nm sizes. Deformation up to e=10 and more does not cause changes of NC structure.

Deformation of metals at 80K also results in formation of NC structure, but with the smaller grain sizes and higher level of hardening. The maximum level of vanadium hardness after cold deformation (300K) makes 2.7 GPa from initial condition - 0.75 GPa, the hardness grows by 4.5 times after low temperature deformation (80K). The general level of niobium hardness grows by 1.7 times from initial after cold deformation. Measurements of niobium hardness have shown deformation leads to steady growth of hardness up to e=9 at room temperature and the saturation stage of Nb hardness is not achieved unlike V in the same interval of deformations.

Structural changes of the V-Zr-C-alloy, as a whole, are similar to the changes, occurring in the V and Nb. However specific feature of the alloy is the behavior of carbides at deformation, so there are carbides broken on fragments and unchanged carbides after deformation.

 

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Presentation: poster at E-MRS Fall Meeting 2005, Symposium I, by Tatiana M. Teterina
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-04 09:15
Revised:   2009-06-07 00:44