Experimental and numerical study on microstructure and mechanical properties for laser welding-brazing of TC4 Titanium alloy and 304 stainless steel with Cu-base filler metal

Abstract

Laser welding-brazing of TC4 Titanium (Ti) alloy to 304 stainless steel (SS) has been applied using 38Zn-61Cu alloy as filler metal. Microstructures of the joints were studied using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Mechanical properties of the joints were evaluated by performing tensile tests. The temperature field and stress field distributed in laser welding based on SS-Ti alloy joint were dynamically simulated using the ANSYS in this study. 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 process was one pass welding involving creation of a joint with one fusion weld and one brazed 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, the filler metal melted occurred at the SS-Ti alloy interface. A brazed weld was formed at the SS-Ti alloy interface with the main microstructure of (Fe, Zn)+Fe3Zn7, β-CuZn and β-CuZn + Ti2Zn3. The joint fractured at the brazed weld with the maximum tensile strength of 210 MPa. By comparing the simulation results with the corresponding experimental findings, the validity of the numerical model is confirmed.