等通道双转角挤压及热处理N36锆合金析出行为及机理研究

Research on Precipitation Behavior and Mechanism of N36 Zirconium Alloy by Equal Channel Double Angular Pressing and Heat Treatment

摘要:

形变热处理是细化核反应堆包壳材料Zr-Sn-Nb-Fe（N36）合金沉淀相尺寸、促进其弥散分布，进而提升服役性能的有效手段。本研究对N36合金进行了450 ℃下4道次等通道双转角挤压（equal channel double angular pressing，ECDAP）大变形和580 ℃保温4~8 h时效处理。采用光学显微镜（OM）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）对沉淀相尺寸、数量、成分及分布进行了表征。结果表明：时效处理促进了(Zr,Nb)₂Fe沉淀相粒子析出，经过580 ℃保温4~8 h的时效处理后，初始样析出的沉淀相粒子平均尺寸由76 mm增加至88 mm。4道次变形样析出的沉淀相粒子平均尺寸由41 mm增加至51 mm，并且析出一定数量尺寸在20~40 nm的(Zr,Nb)₂Fe相。等通道双转角挤压试样中含有较多的位错和缺陷，为后续时效处理过程中沉淀相粒子的析出提供形核点，并为合金元素提供了短途扩散通道，从而促进沉淀相粒子细小弥散析出。本研究为提升N36合金综合性能提供新的思路。

Abstract:

Thermoforming treatment is an effective method to refine the precipitate size of N36 alloy, promote its dispersion distribution, and improve its service performance in nuclear reactor cladding materials. In this study, Zr-Sn-Nb-Fe (N36) alloy subjected to 4 passes of equal channel double angular pressing (ECDAP) at 450 ℃ for large deformation and aging treatment at 580 ℃ for 4–8 h. The microstructures were characterized by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that aging treatment promotes the precipitation of (Zr,Nb)₂Fe precipitate phase particles, and after aging treatment at 580 ℃ for 4–8 h, the average size of the precipitate phase particles in the initial sample increases from 76 mm to 88 mm. The average size of precipitate phase particles in the samples after 4 passes of deformation increases from 41 mm to 51 mm, and a certain amount of (Zr,Nb)₂Fe phase with a size of 20–40 nm is precipitated. ECDAP sample contains a large number of dislocations and defects, which provide nucleation points for the precipitation of precipitate phase particles during subsequent aging treatment and a short diffusion channel for alloying elements, thereby promoting the fine dispersion and precipitation of precipitate phase particles. This study provides new ideas for improving the comprehensive performance of N36 alloy.