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

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 with high temperature and high pressure, the lubrication 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 microstructure 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 degrees C, and the microstructure of the longitudinal section of the extrusion was characterized by electron backscattered diffraction technique. The analysis shows that the coating has the best lubricating effect at 680 degrees C, 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 <10<(0)over bar>0>//ED extruded silk texture. The research results have a certain guiding role for improving the extrusion lubrication process of zirconium alloy and optimizing the microstructure and performance of extruded parts.