Tensile creep behavior of the Zr-2.5Nb alloy tubes having outer diameters of 90 mm and 110 mm, processed by extrusion and forging, respectively has been studied in the temperature range of 350-450°C under the stress range of 82-319 MPa. The creep curves have shown that the minimum creep rate and time to rupture changes with the applied stress and temperature. The apparent activation energy of creep $\left(Q_C\right)$values, have been determined by using the power law for 90 mm and 110 mm tube samples are found to be ∼ 231 kJ/mol and ∼ 264 kJ/mol respectively, which is significantly higher than that for lattice self-diffusion of Zr (113 kJ/mol). The microstructural examination of the creep-ruptured samples through transmission electron microscopy (TEM) has shown evidence for multiplication of dislocations, along with their interaction with the β-(Nb, Zr) precipitates in the α-Zr matrix, which is mainly contributed to origin of threshold stress during creep. By incorporating the threshold stress data in the modified power-law relation, the true activation energy of creep $\left(Q_t\right)$ values from the samples of 90 mm and 110 mm tubes are found as 118 kJ/mol and 132 kJ/mol, respectively, which are close to that for lattice self-diffusion in Zr. The obtained true stress exponent $\left(n_t\right)$ values of 3.6 and 4.9 and formation of dislocations sub-grains in the power-law regime of steady state creep, which suggests that the dislocation climb is the rate-controlling mechanism. Further, creep data of the alloy are validated by the Monkman-Grant and Modified Monkman-Grant relationship, and time to rupture effectively predicted using the Larson-Miller Parameter. The creep damage tolerance factors are in the range of 1.5-2.5 for the tubes suggest cavity growth mechanism. Additionally, the comparison of creep data with the Ashby-Dyson maps indicates early formation of cavities due to creep.

研究了外径为90 mm和110 mm的Zr-2.5Nb合金管的拉伸蠕变行为，分别在350-450°C的温度范围和82-319 MPa的应力范围内通过挤压和锻造加工而成。蠕变曲线表明，最小的蠕变速率和破裂时间随所施加的应力和温度而变化。蠕变的表观活化能$（{问}_C）$使用幂定律确定的90毫米和110毫米管样品的值分别约为231 kJ / mol和264 kJ / mol，明显高于Zr的晶格自扩散（113 kJ / mol）。通过透射电子显微镜（TEM）对蠕变断裂样品的微观结构检查显示出位错的倍增证据，以及它们与α-Zr基质中的β-（Nb，Zr）沉淀物的相互作用，这主要是由于蠕变过程中阈值应力的起源。通过将阈值应力数据合并到修改的幂律关系中，可以得出蠕变的真实激活能$（{问}_{Ť}）$从90毫米和110毫米管样品中得出的值分别为118 kJ / mol和132 kJ / mol，这与Zr中晶格自扩散的值接近。获得的真实应力指数$（{ñ}_{Ť}）$稳态蠕变的幂律状态下，3.6和4.9的值和位错亚晶粒的形成，表明位错爬升是速率控制机制。此外，该合金的蠕变数据通过Monkman-Grant和修正的Monkman-Grant关系进行验证，并使用Larson-Miller参数有效预测破裂时间。管的蠕变损伤容限因子在1.5-2.5范围内，表明腔体生长机理。此外，蠕变数据与Ashby-Dyson贴图的比较表明，由于蠕变会较早地形成空腔。