工业纯锆室温蠕变性能及显微组织研究

Creep Properties and Microstructure of Commercial Purity Zirconium at Ambient Temperature

摘要:

本文分别研究了不同状态工业纯锆在0.9R_p0.2、0.925R_p0.2、0.95R_p0.2、0.975R_p0.2蠕变应力下的室温蠕变性能，计算了不同状态工业纯锆的稳态蠕变速率及蠕变应力，并分析了退火前后以及蠕变前后工业纯锆的微观组织。试验结果表明：不同状态工业纯锆的室温蠕变均存在阈值应力，当外加蠕变应力大于阈值应力时，随着蠕变应力的增加，工业纯锆位错密度显著增加，晶界处呈现出明显的位错塞积现象；与粗晶工业纯锆相比，经250°C退火处理后的超细晶工业纯锆，既能维持晶粒尺寸及稳定的显微组织状态，同时还能保证原有的高强度并提高其塑性；另外，250°C退火处理显著提高超细晶工业纯锆室温蠕变性能，使室温蠕变应力敏感性降低，室温蠕变抗性增加。

Abstract:

The creep tests were carried out on commercial purity zirconium (CP-Zr) in different states under the stresses of 0.9R_p0.2、0.925R_p0.2、0.95R_p0.2、0.975R_p0.2 at ambient temperature (AT). Steady state creep rate and creep stress were calculated. The microstrutures of CP-Zr before and after annealing and creep tests were analysied. The results indicate that the threshold stress of CP-Zr in different states exists in creep tests at AT. When the creep stress is greater than the threshold stress value, the density of dislocation of CP-Zr obviously increases with the creep stress increasing, the significant dislocation pile-up can be observed at grain boundaries. It is found that the UFG CP-Zr after annealing at 250°C can not only maintain grain size and stable microstructure, but also keep the original high strength and improve the plasticity compared with CG CP-Zr. In addition, the annealing treatment at 250°C can improve the creep properties of UFG CP Zr, weaken the creep stress sensitivity and enhance the creep resistance.