Microstructural and Mechanical Evolution in Stainless Steel Clad Carbon Steels via FSW

Abstract

Friction Stir Welding (FSW) has emerged as an effective solid-state joining technique for producing high-quality stainless steel–clad carbon steel structures for advanced structural and corrosion-resistant applications. This study investigates the microstructural transformation and mechanical property evolution occurring during FSW-based cladding of carbon steel with stainless steel. Detailed metallographic and scanning electron microscopy analyses reveal the formation of a refined, dynamically recrystallized stir zone characterized by homogeneous material mixing and the elimination of solidification-related defects typically observed in fusion welding. The interfacial region exhibits continuous metallurgical bonding with limited intermetallic formation, indicating favorable diffusion-controlled interaction between the dissimilar metals. Grain refinement and phase redistribution significantly enhance hardness and tensile strength within the weld nugget, while maintaining acceptable ductility. Mechanical testing demonstrates improved load-bearing capacity and interfacial integrity of the clad system compared to the base materials. The results confirm that FSW enables the production of defect-minimized, mechanically reliable stainless steel–carbon steel composites with superior structural performance and service durability.