Interfacial Bonding Mechanism of 12Cr Oxide Dispersion Strengthened Steel Joint by Solid-state Resistance Butt-welding

Due to the high density of dispersed nano-oxides, Oxide dispersion strengthened (ODS) alloys exhibit excellent radiation, corrosion resistance and high temperature stability, making them promising candidate materials for nuclear applications. Currently, one of the critical challenges lies in achieving reliable welding combined with high density of dispersed nano-oxides in the welding joints, especially for thin-walled structures. The present study proposed a modified resistance butt welding, and achieved sound metallurgical bonding in thin-walled ODS steel T-joint through continuous dynamic recrystallization(CDRX) with a comparable nano-oxide average size 8.09 nm and number density 1.8×1022 m-3 to the base metal (5.12 nm and 5.5×1022 m-3). In the initial stage of welding, the joint is partially bonded, and contains a large number of interfacial voids. With the increasing welding time, the voids heal and some interfacial oxides remain at the interface. By increasing the welding time further, the amount of residual interfacial oxides decreases and the joint achieves metallurgical bonding. Three types of CDRX mechanism occur during welding, Ball-Hutchison model and core-mantle model caused by grain boundary sliding, and conventional CDRX caused by intragranular deformation. Prolonged welding time causes grain coarsening and nano-oxide particle growth, accompanied by a reduction in number density, which induces a transition in tensile fracture from ductile to brittle.