The study of dissimilar metals’ welding is an important issue due to their increasing applications in many industrial fields. Welding of dissimilar metals is challenging because of the formation of large residual stress and brittle intermetallic compounds (IMCs). In order to solve this problem, intermediate interlayers were used to eliminate or inhibit the formation of brittle intermetallic reaction layers in many welding techniques, such as diffusion bonding, laser welding, electron beam welding, and other welding techniques. The aim of this paper is to review the recent progress of dissimilar metals’ welding methods and mechanisms with interlayer to offer a basis for the following research. The work discussed several criteria for the selection of interlayer, such as physical properties, metallurgical compatibility, mode, and thickness of the interlayer. Then, formation enthalpy, Gibbs energy of formation (ΔG), and brittleness of the IMCs, as well as welding parameters, were also discussed. Simultaneously, the present work had proposed a design guideline for the selection of interlayer in dissimilar metals’ welding to acquire a welded joint with good quality.

A review on dissimilar metals’ welding methods and mechanisms with interlayer

High-quality joints between titanium alloys and stainless steels have found applications for nuclear, petrochemical, cryogenic, and aerospace industries due to their relatively low cost, lightweight, high corrosion resistance, and appreciable mechanical properties. This article reviews diffusion bonding between titanium alloys and stainless steels with or without interlayers. For diffusion bonding of a titanium alloy and a stainless steel without an interlayer, the optimized temperature is in the range of 800–950°C for a period of 60–120 min. Sound joint can be obtained, but brittle FeTi and Fe-Cr-Ti phases are formed at the interface. The development process of a joint mainly includes three steps: matching surface closure, growth of brittle intermetallic compounds, and formation of the Kirkendall voids. Growth kinetics of interfacial phases needs further clarification in terms of growth velocity of the reacting layer, moving speed of the phase interface, and the order for a new phase appears. The influence of Cu, Ni (or nickel alloy), and Ag interlayers on the microstructures and mechanical properties of the joints is systematically summarized. The content of FeTi and Fe-Cr-Ti phases at the interface can be declined significantly by the addition of an interlayer. Application of multi-interlayer well prevents the formation of intermetallic phases by forming solid solution at the interface, and parameters can be predicted by using a parabolic diffusion law. The selection of multi-interlayer was done based on two principles: no formation of brittle intermetallic phases and transitional physical properties between titanium alloy and stainless steel.

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A Review on Diffusion Bonding between Titanium Alloys and Stainless Steels

Inhomogeneous interface structure and mechanical properties of rotary friction welded TC4 titanium alloy/316L stainless steel joints

Titanium (Ti)/steel clad plates with interlayer material of interstitial free (IF) steel, vanadium (V) and IF steel + V were successfully fabricated by hot roll bonding method at temperature of 850, 900 and 950 °C. Tensile shear test and tensile test were performed to evaluate the mechanical properties of the Ti/steel clad plates. The interfaces and the fracture surfaces of Ti/steel clad plates were carefully characterized by scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction. The results reveal that the interlayer materials have influence on the compounds at the Ti/steel interfaces. Carbides are detected at the interfaces of Ti/steel with single IF steel or V interlayer. The formation of carbides impairs the shear strength of clad plates. σ phases instead of carbides are observed at the interface of Ti/steel clad plate with IF steel + V interlayer, which is beneficial for the tensile shear strength. Rolling temperature also has significant influence on mechanical properties of Ti/steel clad plates. The thickness of σ phase increases with the increase of rolling temperature. Thick σ phases impair the mechanical properties of the Ti/steel clad plate.

Zhanling Qin

Papers

Influence of vanadium filler on the properties of titanium and steel TIG welded joints