Strength improvement and interface characteristic of TC4 Ti alloy and 304 stainless steel joint based on a hybrid connection mechanism

Abstract

Laser welding of TC4 Titanium (Ti) alloy to 304 stainless steel (SS) has been applied using Ag73-Cu16-Zn11 alloy as filler metal. A new welding process for SS-Ti alloy joint was introduced on the basis of the controlling the formation of Ti-Fe intermetallics in the joint. One pass welding involving creation of a joint with one fusion weld and one diffusion weld separated by remaining unmelted SS. When laser beam on the SS side was 1.5 mm, SS would not be completely melted in joint. Through heat conduction of unmelted SS, the atomic diffusion occurred at the SS-Ti alloy interface. A diffusion weld was formed at the SS-Ti alloy interface with the main microstructure of γ-Fe + Fe3Zn2, AgZn3 + Cu5Zn8 and α-Ti + Ti2Cu. The joint fractured at the diffusion weld with the maximum tensile strength of 129 MPa. Keywords: TC4 Ti alloy, 304 stainless steel, Laser welding, Diffusion welding, Microstructure, Filler metal