چكيده به لاتين
Creating highly resistant joints between titanium alloys and stainless steel has many industrial applications. Among the applications of this joint are military, chemical, nuclear and aerospace applications. Welding these two alloys is very difficult due to the large difference in physical properties between the two alloys. The main problem in joining two titanium alloys and stainless steel is the formation of brittle FeTi phases, which are very brittle and cause post-welding cracks. Various intermediate layers such as V, Mg, Al, Ni, Ag, Cu and Ta are used to join these two alloys. Considering the advantages of the copper layer, it was used as an intermediate layer for laser welding of titanium alloy to stainless steel. Laser welding of titanium and 304 stainless steel sheets with a thickness of mm2 and a copper sheet as an intermediate layer with a thickness of mm1 was carried out at laser powers of 5, 3/5, 4, 3/6, 5, 4 kV and welding speed of m/min2. The fracture characteristics of the joints were investigated using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction analysis. The fracture surface studies showed that the joints were dependent on the change in laser power, both in terms of weld strength and fracture location. The optimum value for the maximum tensile strength of the joints was obtained up to 300 MPa at 4 kW. As the laser power increased to 4 kW, the tensile strength increased; but as the power exceeded 4 kW, this strength decreased. In the 4 kW samples, the fracture characteristics showed that there was a larger amount of copper remaining on the titanium sheet, which caused the fracture path to be biased towards the copper interface layer. Fracture imaging studies showed that the fracture surface of the 4 kW weld had a rougher area than the 3 and 6 kW welds. XRD results also showed that most of the solid solution phases, such as αTi, (V) and (Ni) which are present in various types of aluminum intermetallic alloys, can exist at the weld failure level of 4 kW. Also, in order to achieve the best quality in the dissimilar joint, welding experiments were also conducted at 3 laser focus positions. The best laser position was obtained at the Cu-SS interface, which will make the ductility and tensile strength of the joint to a higher extent than the different laser positions.
