Plastic Deformation of Zr-Based Alloys at Temperatures of Phase Transformations

Abstract

Deformation behavior of Zr-Nb alloys under uniaxial compression, accompanied by phase transformations, is considered by the example of Zr-1%Nb and Zr-2.5%Nb alloys. Model samples were deformed at temperatures of β- and (α+β)-regions of the phase diagram Zr-Nb. Mechanisms, responsible for plastic deformation of alloys by different temperature-rate regimes, were determined on the basis of textures, arising in deformed samples. Among these mechanisms there are crystallographic slip in grains of β-Zr and α-Zr as well as mutual displacements of crystallites along interphase boundaries. The latter mechanism sharply intensifies under conditions of α↔β phase transformations and lies in the basis of superplasticity. An input of each mechanism into plastic deformation of material depends on the temperature-rate regime of compression and determines its anisotropy.

Development of texture inhomogeneity in sheets from Zr-based alloys under high-temperature rolling

“…Then it follows from experimental data, presented in Figure 1 corresponding growth of local temperatures. When the deformation rate is sufficiently high, operation of deformation mechanisms is accompanied by heat generation and local warming-up of material, so that within some microvolumes the initial phase equilibrium can be broken and additional portions of -phase arise, as it was shown earlier as applied to forging of Zr-based alloys [2][3].…”

“…Under hot rolling by route B with smaller reductions per pass the effects of cooling become more significant, since material of the sheet contacts with rolls during a longer time, than by route A, and by the lower deformation rate the deformation-induced warming-up of material [2][3] proves to be less essential. As a result, the temperature of inner layers under rolling of the sheet decreases as well as the content of -phase.…”

“…Textures of successive layers form by means of different predominant mechanisms, among which there are crystallographic slip in the high-temperaturephase with BCC crystalline lattice + phase transformation, crystallographic slip in the lowtemperature -phase with HCP crystalline lattice, non-crystallographic mutual shifts of crystallites by interphase boundaries. As applied to forging of Zr-based alloys at various temperature-rate regimes, effects of these mechanisms on the deformation texture of products were described in detail [2][3]. Under hot rolling, in contrast to forging, the regime of deformation changes by passing from layer to layer because of the essential temperature gradient near rolls.…”

Comparative Possibilities of Different X-Ray Methods by Study of SPD Metal Materials

“…Whereas operation of crystallographic deformation mechanisms leads to development of crystallographic textures, operation of non-crystallographic mechanisms, accompanied by accidental rotations of results in texture scattering. As a measure of texture scattering, the angular width of texture maxima or the value of textureless component are used [7].…”