Zirconium remains the main structural material for thermal reactors due to the small capture cross section of thermal neutrons. In the period of stricter safety requirements for reactors with a simultaneous increase in operating parameters, predicting the behavior of the material in emergency situations has gained greater urgency. In this work, we measured the temperature dependence of the thermal expansion of samples cut from thick-walled tubes made of Zr-2.5% Nb alloy that were deformed and annealed in different modes. The analysis of the physical processes responsible for the shaping of the material is carried out. It was found that the anisotropic change in the linear dimensions of cubic samples both during heating and cooling is due to a change in the zirconium content in the β-phase, phase transformations α + β-Zr → α + β-Nb → β → α + β-Zr, as well as the preferred orientation of the grains of the α-phase, characterized by high anisotropy of linear expansion. It is shown that the expansion of the investigated samples upon heating in the α -phase is determined exclusively by the integral texture parameters of Kearns, and the coefficients of thermal linear expansion (TLEC) in different directions vary over a wide range from 3⋅10^-6 to 12⋅10^-6 K⁻¹. During cooling at the stage of the reverse phase transformation of the β-phase into α, an increase in the size of the cubic samples in the tangential direction up to 2.3 % and a decrease in the radial direction to 1.3 % are noted, which is associated with the orientation of the α-phase grains formed during cooling in the β -matrix and anisotropy of the TLEC of the α -grains. It is shown that the orientation of the α-phase grains in the reverse β → α transformation is determined not only by the orientation of the basal axes in the initial material, but also by the spatial distribution of the prismatic axes relative to the external directions in the tube. Significant size fluctuations in different directions of the samples obtained using the technology of manufacturing channel tubes for CANDU reactors should lead to the development of significant macrostresses both during heating and cooling of the tube. The structural state of the samples deformed or annealed at 400–530 °C does not significantly affect the temperature dependence of the TLEC, but is manifested only in some of its features. In this case, completely recrystallized samples, i.e., with a recrystallization texture, in which the < 11$\stackrel{-}{2}$0 > directions are oriented along the tube axis, are characterized by a significantly lower variation in dimensions in different directions in the temperature range 20–1200 °C.

由于热中子的俘获截面小，锆仍然是热反应堆的主要结构材料。在反应堆安全要求更加严格且运行参数同时增加的时期，预测材料在紧急情况下的行为变得更加紧迫。在这项工作中，我们测量了从 Zr-2.5% Nb 合金制成的厚壁管上切割的样品的热膨胀的温度依赖性，这些管在不同的模式下变形和退火。对负责材料成型的物理过程进行分析。发现立方体样品在加热和冷却过程中线性尺寸的各向异性变化是由于 β 相中锆含量的变化，相变 α + β-Zr → α + β-Nb → β → α + β-Zr，以及α相晶粒的择优取向，其特征是线膨胀的高各向异性。结果表明，研究样品在 α 相加热时的膨胀完全由 Kearns 的积分织构参数决定，不同方向的热线膨胀系数 (TLEC) 变化范围很广，从 3⋅10^-6到 12⋅10 ^-6 K ^-1. 在 β 相逆相转变为 α 阶段的冷却过程中，注意到立方体样品在切向方向上的尺寸增加了 2.3%，径向方向上的尺寸减少了 1.3%，即与冷却过程中在 β 基体中形成的 α 相晶粒的取向和 α 晶粒的 TLEC 的各向异性有关。结果表明，逆β→α相变中α相晶粒的取向不仅取决于初始材料中基轴的取向，还取决于棱柱轴相对于外部方向的空间分布在管中。使用 CANDU 反应器通道管制造技术获得的样品在不同方向上的显着尺寸波动应导致在管的加热和冷却过程中产生显着的宏观应力。在 400-530°C 变形或退火的样品的结构状态不会显着影响 TLEC 的温度依赖性，但仅表现在其某些特征中。在这种情况下，完全再结晶的样品，即具有再结晶织构，其中 < 11$\stackrel{——}{2}$0 > 方向沿管轴定向，其特点是在 20–1200 °C 的温度范围内不同方向的尺寸变化显着降低。