Solid-state welding for dissimilar zirconium alloy under joule heating effect: Material flowing behavior, characteristics, evolution and formation of interface

Abstract

An in-depth understanding of the mechanism of ultra-fast forming in resistance upsetting welding is the key to obtain high-quality cladding tube-end plug joints. According to the movement characteristics of the end plug (Zr-Sn alloy) to the cladding tube (Zr-Nb alloy), the macroscopic interaction was further revealed. The flow behavior of materials at different welding times was tracked in detail, and the rapid expansion behavior of weld nugget was studied. The electron back scatter diffraction (EBSD) method was used to analyze the grain characteristics and forming mechanism of the weld nugget in different regions, and the spatial and temporal distribution characteristics of the forming mechanism of the joint were established. The forming process of the joint heavily relies on the joule heating effect occurring 8 ms before welding. The ultra-short duration of 20 ms enables the extremely rapid formation of the entire joint. The thermo-mechanically affected zone (TMAZ) gradually evolved from the initial five parts to two parts. The welding process will be accompanied by continuous deformation, multiple dynamic recrystallization (DRX) and grain growth. Despite the differing initial textures of the base metal in the end plug and the cladding tube, the texture characteristics of the fine grain zone (FCZ) after welding exhibit remarkable similarity. The joint exhibits extremely superior mechanical properties. Both tensile and blasting mechanical evaluation methods fractured the base material of the cladding tube.