工业纯锆室温蠕变性能及显微组织

Creep Properties and Microstructure of Commercially Pure Zirconium at Ambient Temperature

研究了不同状态工业纯锆在0.9RP0.2、0.925RP0.2、0.95RP0.2、0.975RP0.2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。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℃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℃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。

The creep tests were carried out on commercially pure zirconium(CP-Zr)in different states under the stresses of 0.9RP0.2,0.925RP0.2,0.95RP0.2 and 0.975RP0.2 at ambient temperature(AT).Their steady state creep rate and creep stress were calculated.The microstructures of CP-Zr before and after annealing and creep tests were analyzed.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 increase of creep stress,and the significant dislocation pile-up can be observed at grain boundaries.It is found that the UFG CP-Zr after annealing at 250℃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℃can improve the creep properties of UFG CP Zr,weaken the creep stress sensitivity and enhance the creep resistance.