Influence of welding speed on microstructures and mechanical properties of vacuum electron beam welded TZM alloy joints

Butt joints of molybdenum-titanium-zirconium (TZM) alloy were welded by electron beam welding (EBW) and the influence of welding speed on the microstructures and mechanical properties of TZM joints were investigated in this paper. The color etching method was performed to obtain the orientation and phase distribution on weld zones (WZs) of the joints welded at different welding speeds. The electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were conducted to further check the results of the color etching method. The results illustrated that the tensile strengths would reduce with the increasing welding speed within a certain range. When welding speed was 350 mm/min, the tensile strength was 403 MPa, while the tensile strength of the joint welded at the welding speed of 390 mm/min was 256 MPa. The segregation of the MoO₂ particles on grain boundaries (GBs) was also promoted with the increase of the welding speed, leading to the decrease of tensile strength and formation of severe intergranular fracture in the WZ.