Abstract
The evolution of texture in Zr-2.5 Nb during uniaxial compression was studied in annealed specimens with α grain sizes of 5 and 10 μm. It is shown that texture development is determined by the mechanism controlling -axis deformation. In fine grained material and slip are found to be responsible for texture evolution. Tensile twinning controls the formation of a sharp [0001] compression texture in coarse grained material. It is suggested that the mode of -axis deformation is determined by the α grain size.
Highlights
The texture of Zr-2.5 Nb CANDU pressure tubes can be described by a single {1210} ideal orientation in which the (0001) plane normals of the crystal grains are aligned parallel to the circumferential direction
Extensive research has been carried out at AECL to find alternative fabrication routes which may lead to pressure tubes with reduced cracking susceptibilities
The research to be described below forms part of this effort and was aimed at characterizing the evolution of texture in hot swaged Zr-2.5 Nb round bar during uniaxial compression
Summary
The texture of Zr-2.5 Nb CANDU pressure tubes can be described by a single {1210} ideal orientation in which the (0001) plane normals of the crystal grains are aligned parallel to the circumferential direction. Two batches of specimens were vacuum annealed 24 hours at two different temperatures, 1073 K and 1123 K, and furnace cooled These produced microstructures consisting of equiaxed u-Zr grains with average grain sizes of 5 gm and 10 @m, respectively. From the (331} planes of a Si crystal monochromator at a diffraction angle of 68 Intensity data were collected for the (0002}, (1010), (1120), (1011) and (1012) reflections of u-Zr as a function of the tilt angle (0-90 ) from the axial direction of the specimen and the azimuthal angle (0-360 ). Pole figures were plotted with the compression axis (Z) at the centre and the transverse reference direction at the north pole. The evolution of microstructure with deformation was followed using standard metallographic techniques
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