Laser welding of titanium and stainless steel sheets using Ag-Cu interlayers: microstructure and mechanical characterization

Welding of dissimilar materials is an important object and has several industrial applications. In this article, the welding of 316L stainless steel sheets to commercially pure grade 2 titanium alloy (Ti Gr2) will be investigated. A pulsed laser was used for welding the SS/Ti sheets. A single Cu and Ag-Cu thin sheet were used as an interlayer to obtain excellent joint strength. Tensile test, micro-hardness test, scanning electron microscope (SEM) imaging, and energy dispersive spectroscopy (EDX) were implemented to measure the mechanical properties and observe the microstructure of the weld zone. The average tensile strength of the joint with Ag-Cu interlayers is 230 MPa which is approximately 100% higher than the joint strength obtained with a single Cu interlayer. The elongation of the joint with an Ag-Cu interlayer is six times greater than the joint with a single Cu interlayer and direct welding of Ti Grade 2 to 316L stainless steel. The microstructure observation shows that in welding with Ag-Cu interlayers, the Ag-Cu solid solution phase will form instead of Fe-Ti intermetallic particle formation. In addition, the amount of Ti-Cu brittle components decreases by adding the Ag element. The Fe-Ti brittle compound also reduces in the weld with Cu interlayer. In the joint with Ag-Cu interlayers, dimples and river patterns in the fracture surfaces were observed. The fractography indicated a mixed fracture mode (brittle and ductile) due to the solid solution of Ag and Cu components.