Microstructure of a Laser-Welded Joint between a Chromium–Nickel Steel and a Titanium Alloy with a Copper Insert

The microstructure of a laser-welded joint between a chromium–nickel austenitic steel and a titanium alloy with an intermediate copper insert has been studied. Using X-ray diffraction analysis, energy-dispersive X-ray microanalysis, and transmission electron microscopy, it has been shown that the welded joint represents a copper-based solid solution with intermetallic particles of (Fe,Cr)2Ti and Cu3Ti 10–50 μm in size, which were the first to crystallize in the welding pool, and intermetallic particles of (Fe,Cr)2Ti and Cu4Ti with a size of no more than 30 nm, which homogeneously precipitate on cooling from the copper-based solid solution oversaturated at the moment of crystallization. The fracture of the joint upon tensile tests occurred along the diffusion zone at the boundary with the titanium alloy. The maximum ultimate tensile strength of such a joint was 474 MPa.