To content large part manufacturing of the airplane

electron beam welding (EBW) was employed on TC4 titanium alloy with 170 mm thickness

which was investigated by the method of induced molten pool flow. The experiments with variable focusing welding were conducted on the plates

which achieved the underfocusing processing under the current of 2415–2400 mA. The maximum of welding depth reaches 162 mm

and weld morphology is parallel

which contributing to the fluidity of molten pool and welding formation. The microstructures in weld area are coarse crystals and acicular martensite α'

which became gradually refining and homogeneity with the welding penetration increasing. The microhardness of the joint presents the saddle-shaped distribution along the cross section

which gradually increases from 337HV to 356HV along welding depth direction. The investigation verified effectiveness of the EBW processing with induced molten pool flow

which can improve the penetration forming

weld morphology

and microstructure uniformity of large-thickness titanium alloys.