The influence of dilution on dissimilar weld joints with high-alloy TRIP/TWIP steels

In dissimilar welded joints without filler materials, the dilution is one of the most important factor for the weldability. Due to other factors, the high quality of the welding seam and a good reproducibility of welding parameters the electron beam can be advantageously used to join challenging materials. Several dissimilar welded joints were successfully produced as a result of an optimised variation of the beam offset and the beam current to achieve suitable levels of dilution. For microstructural evaluation, the welded joints were examined by light optical and scanning electron microscopy methods, such as Electron Backscatter Diffraction (EBSD) and Wavelength-dispersive X-ray spectroscopy (WDS). To characterise the mechanical properties and the deformation behaviour of the welded material, microhardness measurements and tensile tests were carried out. For the welds of a high-alloy TRIP steel and the steel DP590, an optimised dilution lead to flawless joints with a tensile strength superior to the TRIP steel. Furthermore, welds of a zirconia-reinforced TWIP steel with an as-cast TRIP steel free of pores and cracks could be produced.