Regularities of Changes in Kearns Texture Coefficient at Cold Rolling of Zr-2.5%Nb Alloy

V.m Grytsyna ,Olena Slabospitskaya ,D.g Malykhin ,K.v Kovtun ,T P Chernyayeva ,Vira Kornyeyeva ,Irina Tantsura ,Tetiana Yurkova ,Г П Ковтун ,V.n Voyevodin

doi:10.26565/2312-4334-2019-2-06

V.m Grytsyna , Olena Slabospitskaya + Show 8 more

Open Access

https://doi.org/10.26565/2312-4334-2019-2-06

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Abstract

-ray studies of the changes in characteristics of crystallographic texture with cold deformation of Zr‑2.5%Nb alloy plates by longitudinal and cross rolling up to 56% at the speed of 5…10 sec-1 were carried out. The original plates were made from longitudinal fragments and rings cut from Æ15.0´1.5 mm² tube, and were then annealed at 580 °C. Texture of the plates was studied by the method of inverse pole figures with calculation of the Kearns texture coefficient along the normal to the plate plane. Dependences of the texture coefficient on degrees of deformation of the plates are built. A discrepancy was found between texture coefficient values measured on different sides of the plates, which is associated with the straightening of the original tube fragments and invariance of “c”-axes distribution after subsequent annealing of the initial plates. By introducing corrections to the degree of deformation calculated from the parameters of the cross section of the original tube, such discrepancies were eliminated for the data on cross-rolling of the material. As a result, for both deformation schemes, two stages of changes in the texture coefficient with alloy deformation were revealed: the initial stage of its growth and the subsequent stage of minor changes. Both stages are mainly linear and have the boundary value of the texture coefficient equal to 0.65...0.68. To study the structural mechanisms of changes in the texture of the alloy, an original technique of comparative analysis of changes in the texture coefficient of the material and in the distribution of crystallographic orientations is applied. It is established that at the initial stage of changes in the texture coefficient with deformation in both schemes, the rotation of the crystallographic “c” axes of the material occurs abruptly, and it does at angles of more than 60°. This confirms the essential role of twinning in the texture changes of the alloy. In particular, we have shown that the initial stage is significantly dominated by the {102}á011ñ system of tensile twins. Connection of twinning with differences in texture changes at the longitudinal and cross rolling of the alloy is discussed.

Highlights

Figure 2 shows the inverse pole figures (IPFs) plotted according to the results of texture measurements on the original Zr-2.5%Nb tube along its radial, axial, and tangential directions
In the coordinates of longitudinal plate rolling, it corresponds to the normal direction (ND), the rolling direction (RD) and the transverse direction (TD), respectively
The material of tubes made from zirconium-niobium alloys remains an exceptional subject for textural studies, since it differs from plates, with their usual prehistory, by a more moderate initial texture, – since, according to the analysis of subsequent data, under normal conditions for plate treatment, this alloy will lose the exceptionality after rolling by 60% or more

Summary

Introduction

In contrast to the method of direct pole figures widely used in recent times for texture studies, its prototype – the X-ray method of inverse pole figures (IPFs) [9,10,11] – has retained its principal advantages of simplicity and accuracy of defining the texture characteristics of materials that have biaxial crystallographic anisotropy and show quantitative relationship with the above characteristics of products. This applies to tubes made of zirconium alloys used in fuel assemblies of reactors on thermal neutrons.

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