Investigation on the microstructure and mechanical properties of Ti–6Al–4V alloy joints with electron beam welding

Titanium and its alloys have excellent combination of properties, and they are extensively used in many industrial fields. However, due to their special weldability, the welding of titanium alloys is always of concern to many researchers. This work is aiming at investigation of the effect of different beam scanning patterns on the microstructure and mechanical properties of Ti–6Al–4V alloy joints by electron beam welding. The circular scanning pattern and linear scanning pattern are employed respectively during welding. Results show that the weld metal is full of cross–cross acicular α′ martensitic structure, while the base metal is of equiaxed structure. Mechanical property tests indicate that the hardness of weldment is higher than that of heat-affected zone (HAZ) and base metal. The tensile strength of joint is almost equal to that of base metal, and it is well in accordance with the relationship between microstructure and mechanical properties of welded joints. The tensile fracture morphology of joint presents obviously the characteristic of ductile fracture, which is related to the bigger and deeper dimples distributed on the surface of joint. The circular scanning pattern makes the joint microstructure coarse, while the linear scanning pattern meets the requirement of fining grains by uniform distribution of alloy elements or big grains being broken.