Effects of solution treatment on laser welding of Ti–6Al–4V alloy plate produced through wire arc additive manufacturing

Abstract

Laser beam welding (LBW) had been successfully applied to the welding of Ti–6Al–4V plates by wire arc additive manufacturing. The effects of solution treatment on microstructure, tensile properties, and microhardness after LBW in different deposition directions were studied. When the wire speeding was 3 m/min and travel speed was 0.36 m/min, the difference in mechanical properties was related to the anisotropy of the microstructure. The long columnar grain along the building direction could provide an α path with a large aspect ratio and high elongation. More grain boundaries are present along the scanning direction than in others, showing high strength. The microstructure of the as-deposited condition mainly consists of coarse prior-β grains, partial basket-weave structure, and numerous martensite α′ phase. In LBW without solution treatment, the microstructure of the welds mainly consists of a large amount of martensite α′ and a small amount of basket-weave structure. The weld had high strength and hardness. The tensile strength was between 930 and 970 MPa. The hardness was between 415 and 456 HV. The elongation ranged from 5% to 7%. Afterwards, the temperature was maintained at 870◦C for 2 h, cooled to 600◦C in the furnace for 1 h, and finally air cooled to room temperature. The martensite α′ was almost completely transformed into platelet α. The microstructure of the welds mainly consists of partial β grains, thimbleful martensite α′, and a large of α path. The strength and hardness of the welds were reduced. The tensile strength is between 910 and 950 MPa. The hardness was between 398 and 445 HV. However, the elongation was significantly improved, and the elongation ranged from 10% to 12%.