The effect of constraint conditions on microstructure and properties of titanium alloy electron beam welding

Abstract

In the actual production, when the structures are welded, the weld inevitably bears the constraint stress which changes the internal stress state of the weld, and the properties of welding in actual welding structure are different from those in welding sample, so the effect of constraint stress on the microstructure and properties of electron beam welded joint is revealed by the characterization of solidification microstructure of joint under constraint conditions. The results show that the constraint conditions have a great influence on the microstructure, microhardness and properties. The unevenness of the microstructure of the weld increases, the grain size difference increases, the martensite is smaller with a lot of dislocations, and the continuous grain boundary α phase appears. The fusion zone and the heat affected zone consist of fine acicular martensite and residual α with dislocation tangles. The microhardness distribution of the weld is saddle-shaped, and the microhardness of weld metal is the highest. The tensile strength of the constraint welds is 898 MPa, which is higher than conventional EBW joints, and the fracture position is located in the weld. Due to the existence of a large number of dislocations in the martensite under the constraint condition, the hardness and difficulty of slip deformation increase.