【作者】 李瑞；

【导师】 张聪惠； 朱文光；

【作者基本信息】 西安建筑科技大学 ， 材料与化工（专业学位）， 2023， 硕士

【摘要】 由于出色的耐腐蚀性、良好的加工性能以及较低的热中子吸收截面,锆合金已经成为核工业、化学和海洋领域的理想材料。轧制作为锆合金生产的关键步骤,在调控组织和性能中起到了重要作用。由于锆合金的服役环境极为苛刻,同时面临燃料燃耗提高等问题,对锆合金的设计提出了更高的要求。因此,优化并探索新的轧制工艺对改善锆合金的堆内服役性能至关重要。目前针对锆合金的轧制研究集中在常规轧制,且主要关注成品板材后续的轧制研究。本文在研究ZIRLO合金的变形机制的基础上,通过β单相区处理获得均匀化锆合金并对其进行常规和交叉轧制,探讨了不同轧制方式对组织及力学性能的影响。同时研究了异步轧制对两种状态ZIRLO合金的组织及力学性能的影响,为优化锆合金的生产工艺提供新的途径。取得的主要研究结果如下:对ZIRLO合金进行室温及液氮温度不同方向的轧制实验,对比分析了不同轧制条件下变形机制的差异。结果表明:ZIRLO合金在室温和液氮温度下轧制均以滑移为主变形机制且随变形的增大以柱面滑移为主的晶粒数量下降,液氮温度轧制时{10(?)2}拉伸孪晶多于室温轧制。沿TD方向轧制时,小变形量时激活更多的孪晶协调变形,大变形量时塑性变形以滑移为主;相比RD方向,沿TD方向轧制大变形量时基面和锥面滑移活性更高。针对β处理态锆合金开展常规轧制和交叉轧制,分析了不同轧制方式的组织及力学性能差异。结果表明:交叉轧制使位错在组织中均匀分布,有利于板条破碎获得更加均匀的组织。轧制形成基面织构且织构的强度与变形量相关。交叉轧制在保留非基面织构组分上具有一定的优势。交叉轧制后的强度高于常规轧制,而塑性相当。对不同初始状态的ZIRLO合金板材进行同步轧制和异步轧制实验,对比了两种轧制方式的差异。结果表明:相同变形量下,异步轧制的位错密度更高,晶粒细化程度比同步轧制略大。异步轧制并未改变0°样品的织构,但使90°样品由TD织构变为双峰基面织构,且强度随变形量的增大而增强。与同步轧制相比,异步轧制可以降低ZIRLO合金的法向取向因子,提高横向取向因子。异步轧制显著提高了合金的强度,当变形量相同时,异步轧制的强度高于同步轧制,且塑性较好。异步轧制试样的宏观断裂方式为韧性断裂,其韧窝更深。更多还原

【Abstract】 Zirconium alloy has become an ideal material in the nuclear industry,chemistry and marine due to its excellent corrosion resistance,good processability and extremely low thermal neutron absorption cross section.As a key step in the production of zirconium alloys,rolling plays an important role in the regulation of their microstructures and properties.Since the service environment of zirconium alloy is extremely harsh,while facing issues such as fuel combustion enhancement,higher requirements have been put forward for the design of zirconium alloys.Thus,Optimizing and exploring new rolling processes is essential to improve in-reactor service properties of zirconium alloys.At present,the research on zirconium alloy rolling focuses on conventional rolling,and mainly focuses on the subsequent rolling research of finished plates.In this paper,on the basis of studying the deformation mechanism of ZIRLO alloy,the homogenized zirconium alloy was obtained byβtreatment and subjected to conventional rolling and cross rolling,and the effects of different rolling methods on the microstructure and mechanical properties were analyzed.At the same time,the effect of asymmetric rolling on the microstructure and mechanical properties of ZIRLO alloy in two states was studied,which provided a new way to optimize and improve the production process of zirconium alloy.The main research results are as follows:The rolling experiments of ZIRLO alloy in different directions were conducted at room and liquid nitrogen temperature,and the difference of deformation mechanism under different rolling conditions was analyzed.The result show that deformation mode of ZIRLO alloy is mainly slip and the number of grains dominated by prismatic slip decreases with the increase of the reduction at both room temperature and liquid nitrogen temperature.The{10(?)2}tensile twins rolling in liquid nitrogen temperature are more than those in room temperature.When rolling along the TD direction,more twins coordinated deformation are activated when the deformation is small,and the plastic deformation is mainly slip in large reduction.Compared to the RD direction,the basal and pyramidal slip activity is higher when rolling large reduction along the TD direction.Conventional rolling and cross rolling were carried out forβ-treated zirconium alloy,and the differences of mechanical performances and microstructure of different rolling methods were analyzed.The results show that cross rolling makes the dislocations distributed evenly in the microstructure,which is beneficial to the fracture of lath and obtaining more uniform microstructure.After rolling,a basal texture is formed and the texture strength is related to the reduction.Cross rolling has certain advantages in retaining off-basal texture components.Higher strength is obtained after cross rolling than conventional rolling,and the plasticity is equivalent.The symmetric rolling and asymmetric rolling experiments of ZIRLO alloy plates with different initial states were carried out,and the differences between the two rolling methods were compared.The results show that the dislocation density in asymmetric rolling is higher and the grain refinement is slightly larger than that in symmetric rolling with the same reduction.Asymmetric rolling does not change the texture of 0°sample,but changes the texture of 90°sample from TD texture to bimodal basal texture,and the strength elevates with the increase of reduction.Compared with symmetric rolling,asymmetric rolling can reduce the normal orientation factor of ZIRLO alloy and increase the transverse orientation factor.The strength of the alloy is obviously improved by the asymmetric rolling.When the reduction is the same,higher strength is obtained after asymmetric rolling than symmetric rolling and the plasticity is better.The macroscopic fracture mode of the asymmetric rolled sample is ductile fracture,and its dimple is deeper.更多还原