Corrosion mechanism of TA2/304SS dissimilar Laser welds with Cu interlayer: The synergistic role of microstructural homogenization and protective film formation

This study investigates the corrosion mechanism of TA2/304SS dissimilar laser welds with a Cu interlayer, with a focus on the synergistic effects of post-weld heat treatment (PWHT). While Cu interlayers are known to improve mechanical properties, their electrochemical role and the impact of PWHT on corrosion behavior remain unclear. The results show that PWHT at 700 °C for 30 min transforms dendritic structures into equiaxed grains, significantly reduces residual stress, and decreases the corrosion current density by nearly an order of magnitude. A unique reticulated Cu₂O film forms, which seals micro-cracks and acts as a physical barrier. This work elucidates the synergistic sequence of “microstructural homogenization → protective film formation → self-sealing,” offering a design strategy for durable Ti/steel joints in marine environments.