Effect of beam deviation on electron beam welded Ti-22Al-25Nb/TC4 dissimilar alloys

Abstract

Dissimilar alloys of Ti-22Al-25Nb (at%) and TC4 are welded by electron beam welding (EBW), and the effect of different welding procedures (with electron beam deviation to TC4 side or without) on microstructure and mechanical properties of welded joints are investigated. Results show that the microstructure of fusion zone (FZ) consists of B2 phase and martensitic α′ phase. The heat-affected zone (HAZ) of Ti-22Al-25Nb side near FZ consists of B2 phase and a little of α2 phase, and that of TC4 side near FZ is the α′ phase. When the electron beam is deviated to TC4 side 0.15 mm during welding, the welded joint with good appearance of weld can be obtained, and the ultimate tensile strength and elongation of welded joint reach 967.6 MPa and 3.1%, respectively. The variation of microhardness in weld zone with beam deviation is smaller that of without beam deviation. Electron beam oscillation can stir fully the molten pool during welding, and the main alloying elements distribute uniformly in FZ. On the whole, the mechanical performance of welded joint with beam deviation is better than that of without beam deviation.