Microstructure evolution and mechanical properties of continuous drive friction welded dissimilar copper-stainless steel pipe joints

In the present investigation, the microstructure evolution and mechanical properties of dissimilar materials Copper-Stainless Steel pipe joints welded by continuous drive friction welding under two different processing conditions are analyzed. The processing conditions of friction welding for copper-stainless steel joints are varied by two friction times of 10 s and 15 s while keeping other processing parameters constant. The welded specimens are analyzed for materials characterizations and mechanical testing using optical microscopy and scanning electron microscopy, electron dispersive x-ray spectroscopy, electron backscatter diffraction analysis, X-ray diffractions, tensile testing, and microhardness measurements. The results revealed that the major microstructural evolution is observed at the Cu side with dynamic recrystallized zones. Enhanced metallurgical bonding between Cu-SS materials is obtained with microstructural evolutions (such as full dynamic recrystallized zone at Cu side and quenching zone at SS side) near to Cu-SS interface, in case of weld made by friction time of 15 s. Superior interatomic diffusion leading to enhanced metallurgical bonding is evidenced for weld made by friction time of 15 s. The reaction layer thickness influences the bonding and mechanical properties of Cu-SS friction welds. The reaction layer thickness of 17.28 μm is observed for the weld made by friction time of 10 s, whereas the reaction layer thickness of 1.21 μm is observed for the weld made by friction time of 15 s. The ultimate tensile strength of 181.05 MPa is obtained for Cu-SS friction weld.