润滑对热挤压核级Zr-4合金显微组织的影响

Effect of Lubrication on the Microstructure of Hot Extruded Nuclear Grade Zr-4

摘要:

核级锆合金作为水冷核反应堆的核心结构材料,多采用热挤压工艺加工。然而,在高温、高压等恶劣的热挤压环境下,润滑层极易失效,导致成品件出现缺陷甚至报废。作为挤压过程中至关重要的一环,关于润滑对锆合金挤压件内部组织和性能的影响,目前尚没有过系统的报道。本研究对涂覆二硫化钼润滑剂的Zr-4合金在620 ℃、680 ℃和740 ℃下进行热挤压,并使用电子背散射衍射技术对挤压件纵向截面进行显微组织表征。分析发现涂层在680 ℃下具有最佳的润滑效果,能够促进锆合金内部柱面滑移和锥面滑移的开动,内部晶粒变形均匀,呈现出显著的<01-10>//ED挤压丝织构。研究结果对改进锆合金挤压润滑工艺、优化挤压件的组织和性能有一定指导作用。

Abstract:

As the core structural material of water-cooled nuclear reactors, nuclear grade zirconium alloys are mostly processed by hot extrusion process. However, in the harsh hot extrusion environment such as high temperature and high pressure, the lubricating layer is very easy to fail, resulting in defects or even scrapping of finished parts. As a crucial part of the extrusion process, the effect of lubrication on the internal structure and properties of zirconium alloy extrusions has not been systematically reported. In this study, Zr-4 alloy coated with molybdenum disulfide lubricant was hot extruded at 620 ℃, 680 ℃ and 740 ℃, and the microstructure of the longitudinal section of the extrusion was characterized by electron backscatter diffraction technique. The analysis shows that the coating has the best lubricating effect at 680 ℃, which can promote the starting of the internal cylindrical slip and cone slip of the zirconium alloy, and the internal grain deformation is uniform, showing a significant <01-10>//ED extruded silk texture. The research results have a certain guiding role in improving the extrusion lubrication process of zirconium alloy and optimizing the structure and performance of extrusion parts.