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首页> 外文会议>STP 1467; International Symposium on Zirconium in the Nuclear Industry; 20040613-17; Stockholm(SE) >Review of Deformation Mechanisms, Texture, and Mechanical Anisotropy in Zirconium and Zirconium Base Alloys
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Review of Deformation Mechanisms, Texture, and Mechanical Anisotropy in Zirconium and Zirconium Base Alloys

机译：锆和锆基合金的变形机理，织构和机械各向异性

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摘要

The deformation systems in hexagonal close-packed (hcp) metals are not as symmetrically distributed as in cubic ones. Furthermore, because the primary slip systems are not as numerous and are limited to deformations in the < a > direction, twinning competes with slip in plastic deformation and can, depending on the deformation conditions, play an essential role. In order to explain the conditions in Zirconium and Zircaloy, the well-established relationships of hcp metals are discussed and so are their dependencies on the metal-specific parameters of the hexagonal structure. The interactions between deformation mechanisms and texture formation on the one side and deformation mechanisms and mechanical anisotropy on the other can be likewise transferred to other hcp metals, if one takes into account the differences in dependence of the metal-specific parameters. The low offer of slip systems, their asymmetrical distribution (prism slip in < a > directions and - under constraint - pyramidal slip in < c+a > directions) as well as the strict crystallographic orientation relationships of first and second order pyramidal twinning result in the formation of a strong deformation texture. By virtue of twinning, even small deformation rates lead to large lattice rotations, which change the orientation of the crystallites where all basal poles align in the direction of the compressive force. The fact that in Zirconium and Zirconium base alloys the preferred crystallographic orientation, which is spread in the transverse direction, is also retained as the final stable position is explained by < c + a > pyramidal slip. The decisive factor in texture development is the material flow, the degree of freedom of which is lowest for tube reducing as compared to sheet rolling and wire drawing processes. Therefore tube reducing (characterized by reductions in cross-section R_A, wall thickness R_W, and diameter R_D) permits the most precise predictions of the operative forces and the resulting deformation mechanisms. Systematic investigations on the influence of the reduction parameters on the resulting preferred crystallographic orientation in Zircaloy tubing have shown that the determining factor controlling the texture development is the ratio R_WlR_D. For R_WlR_D > 1, the basal poles align preferentially in the radial direction. For R_WlR_D = 1, the basal poles are randomly distributed in the radial-tangential plane. For R_WlR_D < 1, the basal poles preferentially align in the tangential direction. The sheet texture is identical to the tube texture for R_WlR_D > 1, because in both examples the material flow is characterized by a preponderance of wall thickness reduction. The fiber texture of wire is identical to the texture of tubes for R_W/R_D = i. One can visualize the wire deformation as corresponding to that of concentric tubes with different diameters to comply with tube reduction rates R_WlR_D = 1 under the condition of constant volume. Independent of the fabrication method for the cold-worked semi finished products, a first order prism pole aligns itself parallel to the direction of elongation. (During recrystallization, the basal poles do not change significantly. The basal planes, however, rotate continuously with increasing annealing temperature by ± 30° around their pole, so that in the final stable position, instead of a first order prism pole [cold deformation texture], a second order prism pole becomes parallel to the axial or rolling direction, respectively.) Knowing these dependencies, it is possible to tailor the texture of Zirconium base alloys tubing within the given limits to the requirements in nuclear application.
机译：六方密堆积金属（hcp）的变形系统不像立方金属那样对称分布。此外，由于主要的滑移系统并不多，并且仅限于沿a方向的变形，因此孪生与滑移在塑性变形中竞争，并且可以根据变形条件发挥重要作用。为了解释Zirconium和Zircaloy中的条件，讨论了hcp金属的既定关系，因此它们也依赖于六边形结构的金属特定参数。如果一方面考虑到特定于金属的参数之间的差异，那么一方面变形机理和织构形成之间的相互作用以及另一方面变形机理和机械各向异性之间的相互作用也可以转移到其他hcp金属上。滑移系统的低报价，它们的不对称分布（在方向上的棱镜滑移和-在约束下-在方向上的金字塔滑移）以及一阶和二阶金字塔形孪晶的严格晶体取向关系导致了形成强烈的变形纹理。通过孪晶，即使很小的变形率也会导致较大的晶格旋转，这会改变所有基极在压缩力方向上对齐的微晶的取向。在锆和锆基合金中，优选的沿横向扩展的晶体学取向也保留为最终的稳定位置，这由锥体滑移来解释。织构发展的决定性因素是材料流动，与板材轧制和拉丝工艺相比，材料的自由度对于减少管材而言是最低的。因此，管子的减小（以横截面R_A，壁厚R_W和直径R_D的减小为特征）允许对操作力及其产生的变形机理进行最精确的预测。对还原参数对Zircaloy油管中最终的优选晶体学取向的影响的系统研究表明，控制织构发展的决定因素是比率R_W1R_D。当R_WlR_D> 1时，基极优先沿径向对齐。对于R_WlR_D = 1，基极在径向切向平面中随机分布。对于R_WlR_D <1，基极优先沿切线方向对齐。当R_W1R_D> 1时，薄板纹理与管纹理相同，这是因为在两个示例中，材料流的特征都是壁厚减小。当R_W / R_D = i时，导线的纤维质地与管的质地相同。可以将导线变形可视化为与具有不同直径的同心管的变形相对应，以在体积恒定的情况下符合缩管率R_WlR_D = 1。与冷加工的半成品的制造方法无关，一阶棱镜杆平行于伸长方向对齐。 （在重结晶过程中，基极的变化不大。但是，随着退火温度的升高，基极围绕基极连续旋转±30°，因此在最终的稳定位置，而不是一阶棱镜[冷变形因此，知道这些依赖性，就有可能在给定的核应用要求限制内调整锆基合金管材的织构。

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