Process Review on Dissimilar Metal Joining of Steel and Ti Alloys

Titanium alloys have high specific strength and excellent high-temperature properties. However, Ti alloys have limited weldability with other metals due to the formation of brittle intermetallic compounds. Moreover, when steel is a counterpart of dissimilar metal joining, the soundness of weld is hardly achieved due to weld defects. Numerous studies have been conducted to achieve joint strength by minimizing the effects of Fe-Ti intermetallic compounds. In most studies, pure titanium or Ti-6Al-4V alloy were selected as the Ti base metal, whereas stainless steel, low carbon steel, or alloy steel were selected as the steel base metal. To date, joining processes such as diffusion bonding, brazing, fusion welding, and solid-state joining have been investigated. In this study, the characteristics of each of these joining processes were reviewed. More specifically, the formation of intermetallic compounds was analyzed when Ti alloy and steel were directly joined without using interlayer materials.