Effect of Temperature on Interface Healing of Diffusion‐Bonded Dissimilar Duplex Stainless Steels

Interfacial healing mechanisms during vacuum diffusion bonding of dissimilar duplex stainless steels (DSS) S32304 and S32750 are systematically investigated over a temperature range of 800–1100 °C. The results reveal a strong temperature dependence of atomic diffusion and microstructural evolution. The diffusion coefficient of key alloying elements (Cr, Mo, Ni) increased by 11.3 times (from 1.02 × 10 −15 m 2 s −1 at 800 °C to 1.15 × 10 −14 m 2 s −1 at 1100 °C), which significantly enhanced grain boundary migration and promoted the shrinkage and eventual closure of interfacial voids. Consequently, the interfacial bonding ratio dramatically improved from 25.4% to 91.0%, leading to a progressive enhancement in mechanical properties, with the joint shear strength reaching 813 MPa and microhardness reaching 254 HV. Crucially, at 1100 °C, dynamic recrystallization (DRX) is identified as the dominant healing mechanism, with a recrystallized fraction of 78% at the interface. This process facilitated complete microstructural integration and the formation of a high‐integrity metallurgical bond. This article provides direct evidence establishing DRX as the central mechanism for interfacial healing in diffusion‐bonded dissimilar DSS. At 1100 °C, a high‐strength, defect‐free joint is obtained, providing significant insights for selecting temperatures in solid‐state joining processes.