Relationship between interface heat input and microstructure of titanium/steel composite material was prepared by laser processing

Abstract

Joining of titanium (Ti) alloy and stainless steel (SS) was of great interest for applications in the marine and aerospace fields. Despite the importance, no joining techniques have been developed that avoid the formation of brittle intermetallic compounds (IMCs) to produce high strength joints and ensure good corrosion resistance. Successful joining of Ti alloy and SS was performed by inserting Monel 400 interlayer in this work. Ni and Cu elements in Monel improved corrosion resistance of joints. When the laser focused on the SS side to form an independent molten pool, the diffusion bonding between the Ti alloy and the SS was realized through the heat conduction of the unmelted SS. The presence of the Monel 400 interlayer was performed ensured that crack free welds were obtained and no brittle IMCs were observed. Unmelted SS was retained by laser offset to the SS side to achieve heat transfer to the Monel 400 interlayer. The Monle 400 interlayerwasnot melted, but the eutectic reaction with low melting point still occurredby atomic diffusion. The simulation results showedthat the interface temperature couldbe directly controlled by controlling the welding power, and the simulation results weresimilar to the measured temperature. The diffusion of Ti, Cu and Ni at the Ti/Monel interface formed an obvious reaction layer composed of NiTi and CuTi. It was found that no Ti-Fe IMCs were found. The joint fractured at the Ti-SS interface with the maximum tensile strength of 132 MPa.