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Journal ArticleDOI

Texture evolution in two phase Zr-2.5 wt-%Nb through modified route

01 Oct 2004-Materials Science and Technology (Taylor & Francis)-Vol. 20, Iss: 10, pp 1281-1289
TL;DR: In this article, the texture evolution during fabrication of two-phase Zr-2.5 wt-%Nb was investigated using a modified route, and it was observed that a strong orientation fibre parallel to the working direction develops with hot working (extrusion). With subsequent cold working, the texture formed after extrusion alone becomes strengthened.
Abstract: Two phase Zr – 2.5 wt-%Nb is used as pressure tube material in water cooled and moderated reactors. The in service behaviour of this hcp zirconium based alloy is dependent on strong textures developed during thermomechanical processing. In the present study, the texture evolution during fabrication of this material, using a modified route, was investigated. Texture, evaluated by the orientation distribution function, was correlated to microstructure during various stages of processing. It was observed that a strong orientation fibre parallel to the working direction develops with hot working (extrusion). With subsequent cold working, the texture formed after extrusion alone becomes strengthened. This observation is attributed to the presence of a soft secondary phase (β) at the α-phase grain boundary. In contrast to the above, in the case of single phase Zircaloy 4, new components of texture are generated with cold deformation after hot extrusion, as a result of interaction between grains.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the threshold stress, σth, for reorientation of hydrides in cold worked and stress-relieved (CWSR) Zr 2.5Nb pressure tube material was determined in the temperature range of 523-673 K.

44 citations

Journal ArticleDOI
TL;DR: In this article, both in situ tension and compression tests have been carried out on textured Zr-2.5Nb plate material at room temperature and the evolution of interphase and intergranular strain was determined by the relative phase properties, crystal properties and texture distribution.
Abstract: Both in situ tension and compression tests have been carried out on textured Zr–2.5Nb plate material at room temperature. Deformation along all the three principle plate directions has been studied and the evolution of interphase and intergranular strains along the loading and the principle Poisson's directions has been investigated by neutron diffraction. The evolution of interphase and intergranular strain was determined by the relative phase properties, crystal properties and texture distribution. The average phase behaviors are similar during tension and compression, where the β-phase in this material is stronger than the α-phase. The asymmetric yielding of the α-{0 0 0 2} grain family results in a relatively large intergranular strain in the loading direction during compression and different dependence of strength during tension and compression on texture. The combination of the thermal residual stress and the asymmetric CRSS in the 〈 c 〉 axis gives the {0 0 0 2} grain family a higher strength in compression than in tension.

40 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used tensile tests carried out in the temperature range from room temperature to 800 °C using the samples taken out from a single pressure tube have been used to develop correlations for characterizing the strength parameters' variation as a function of axial location along length of the tube and the test temperature.

17 citations

Journal ArticleDOI
TL;DR: In this paper, the texture evolution of Zr-2.5 Nb alloys is studied for extruded tube in this alloy and it is shown that the texture in both phases strengthens sharply before the β-transus and when both phases are present in similar amounts.

13 citations

Journal ArticleDOI
TL;DR: In this paper, the development of intergranular and interphase constraints in textured Zircaloy-2, Zr-2.5Nb, and Excel alloy during room temperature tension and compression loading in two or three directions relative to the parent texture was reported.
Abstract: We report the development of intergranular and interphase constraints in textured Zircaloy-2, Zr-2.5Nb, and Excel alloy during room temperature tension and compression loading in two or three directions relative to the parent texture. Neutron diffraction was used to track the lattice strain development in the α-phase (all alloys) and β-phase (Zr-2.5Nb and Excel) in three principal directions relative to the parent texture. Zircaloy-2 at room temperature is essentially single phase hcp αZr. The active deformation mechanisms appear to be, in order of increasing critical resolved shear stress, prism (a) slip, basal (a) slip, tensile twinning and pyramidal (c+a) slip. No compressive twinning was observed. Combined with intergranular constraints due to prior thermal treatment, these mechanisms result in substantial asymmetry in the yield stress and lattice strain development (compression versus tension). In Zr-2.5 Nb and Excel, the α-phase appears to deform by the same slip mechanisms as Zircaloy-2, and similar assymmetry of the yield stress and lattice strain development is observed. However, the existence of tensile twinning is not clearly evidenced. The β-phase also deforms by slip, but the critical resolved shear stress is much higher than that for the slip mechanisms in the α-phase, leading to the development of very large interphase constraints in the plastic deformation regime. This is attributed to a combination of solution strengthening of the β-phase (by Nb and, in Excel, Mo) and by grain size.

2 citations

References
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Journal ArticleDOI
TL;DR: In this article, a new variant of the iteration method for the determination of the orientation distribution function (OVF) in arbitrarily defined size of cells in the orientation space, is suggested, in which the centro-symmetrical equivalency of the pole figures is induced by the elements of proper rotations in crystal symmetry.
Abstract: Practical problems of the reproduction of the orientation distribution function (ODF) from pole figures (PFs) using discrete methods (with special attention paid to Imhof's method,) are analysed A new variant of the iteration method for the determination of the ODF in arbitrarily defined size of cells in the orientation space, is suggested The special case, in which the centro-symmetrical equivalency of the PFs is induced by the elements of proper rotations in crystal symmetry, is considered Es werden praktische Probleme der Reproduktion der Orientierungsverteilungsfunktion (OVF) aus Polfiguren (PFn) bei Anwendung diskreter Methoden (bei besonderer Beachtung der Imhof Methode) analysiert Eine neue Variante des Iterationsverfahrens fur die Bestimmung des OVF mit einer Wahlfreiheit der Zellengrose im Orientierungsraum wird vorgeschlagen Es wird ein Spezialfall betrachtet, in dem Elemente der eigentlichen Drehungen in der Kristallsymmetrie eine zentrosymmetrische Gleichwertigkeit in den PFn induzieren

217 citations

Journal ArticleDOI
TL;DR: In this paper, a modified route involving hot extrusion followed by two pilgering operations with an intermediate annealing step was examined in detail, with the main aim of this work being to produce a microstructure and texture which are known to yield a lower irradiation growth.
Abstract: Microstructural changes occurring during the fabrication of Zr-2.5 pct Nb alloy pressure tubes by a modified route, involving hot extrusion followed by two pilgering operations with an intermediate annealing step, have been examined in detail. In the conventional fabrication route, the hot extrusion step is followed by a single cold drawing operation in which the cold work to the extent of 25 pct is imparted to the material for achieving the required mechanical properties. Tensile properties obtained at each stage of fabrication have been evaluated and compared between the two processes. The main aim of this work has been to produce a microstructure and texture which are known to yield a lower irradiation growth. Additionally, suitable annealing conditions have been optimized for the intermediate annealing which annihilates the cold work introduced by the first cold pilgering operation without disturbing the two-phase elongated microstructure. This elongated α+ β I microstructure is required for obtaining the desired level of strength at 310 °C. The final microstructure and the crystallographic texture of the finished pressure tube have been compared with those reported for the conventionally processed material.

103 citations

Journal ArticleDOI
TL;DR: In this paper, a fine two phase structure of α zirconium grains surrounded by a network of a second phase was identified by X-ray diffraction to be cubic β-zircium containing about 20 wt % Nb.

98 citations

Journal ArticleDOI
TL;DR: In this article, a method employing a diverging x-ray beam is described for the determination of preferred orientation in flat transmission samples with a Geiger counter xray spectrometer and it is shown that for a certain range of sample thickness the counting rate is independent of the rotation of the samples, and therefore no correction formula is required.
Abstract: A method employing a diverging x‐ray beam is described for the determination of preferred orientation in flat transmission samples with a Geiger counter x‐ray spectrometer. It is shown that for a certain range of sample thickness the counting rate is independent of the rotation of the samples, and therefore, no correction formula is required.

84 citations

01 Jan 1991
TL;DR: The 9th International Symposium on Zirconium in the Nuclear Industry as discussed by the authors was held in 2008 and the main topics discussed were mechanical properties of ZIRconium alloys, and alloy fabrication.
Abstract: This book contains papers from the 9th International Symposium on Zirconium in the Nuclear Industry. Zirconium alloys, especially Zircaloy-2, Zircaloy-4, and Zr-2.5Nb, have been the main materials used in the core of nuclear power plants. Because of the recent trends in the nuclear industry towards higher fuel discharge burnups for better fuel utilization, and higher heat ratings and coolant temperatures for better thermal efficiency, interest in zirconium alloys has increased. It follows that corrosion-a topic of concern-has high coverage in this book. Other topics discussed are mechanical properties of zirconium alloys, and alloy fabrication.

82 citations