Forming mechanism and mechanical property of pulsed laser welded Ti alloy and stainless steel joint using copper as interlayer

In this work, Cu was used as an interlayer to prevent the formation of these brittle Ti-Fe intermetallics when joining Ti alloy to stainless steel (SS). Microstructures of the joint were analyzed by optical microscopy, scanning electron microscopy, transmission electron microscope and X-ray diffraction. The tensile strengths of the joint were also measured. The laser was focused on the SS side of the joint, which joined the SS and Cu by fusion welding. At SS-Cu interface, a weld zone was formed due to dilution of the Cu and mixing with the SS. At the Ti alloy-Cu interface, a eutectic reaction was responsible for joining. The presence of unmelted Cu interlayer ensured that crack free welds were obtained and no brittle Ti-Fe intermetallics were observed. Tensile strength of the joint can reach to 320 MPa.