Interfacial reaction mechanism of TiBw/Ti6Al4V composites and Inconel 718 alloys by GTAW heat transmission

A good joint of TiBw/Ti6Al4V composites and Inconel 718 alloys was obtained by Gas Tungsten Arc Welding (GTAW) heat transmission. The interfacial reaction mechanism of joint was investigated and analyzed in details. Owing to the heat input applied on the surface of TiBw/Ti6Al4V composites, a solid-state reaction layer appeared at the interface of TiBw/Ti6Al4V composites to Inconel 718 alloys. The thickness of the reaction layer was obviously increased with increasing heat input. Developing of reaction layer mainly depended on the diffusion of elements of Ti and Ni through the interface during welding to form solid solutions and intermetallic compounds (IMCs). The reaction layer can be divided into Ti-rich zone (layer 2) and Ni-rich zone (layer 1). In Ni-rich zone, relatively coarse dendrites were the predominant, however, more brittle IMCs like Ti₂Ni were found in the Ti-rich zone. Micro hardness of reaction layer was much higher than that of base metal. While a slight decrease of hardness was found between Ti-rich zone and Ni-rich zone due to the formation of TiNi.