Effect of Beam Offset of Microstructure and Mechanical Properties of Electron Beam Welding of TZM to Ti-6Al-4V Alloy

Electron beam welding of TZM and Ti-6Al-4V was performed with different beam offsets. A comprehensive analysis was undertaken to evaluate the effects of beam offsets on the joint's microstructure, element distribution, phase composition, and mechanical properties. The microstructure of welded joints underwent a transformation from sporadic dendrite to uninterrupted dendrite structure. With the 0.3 mm beam offset, the fusion zone predominantly comprised martensite. Interestingly, as the beam offset increased, the Mo concentration in the fusion zone decreased from 20 to 1.55 at.%. The phase composition of the welded joints also varied with the beam offset. With a minimal offset of 0.1 mm, the phases ranged from (Mo, Ti) to β-Ti and ω-Ti. As the offset increased to 0.3 and 0.4 mm, the α' phase became dominant. The tensile strength of the joints initially increased first and then reduced in the offset range of 0-0.4 mm. The maximum tensile strength of 480 MPa was obtained at the beam offset of 0.2 mm, while fractured at the heat-affected zone of TZM.