Microstructure and Mechanical Properties of Electron Beam Welded Joints of Ti2AlNb Alloy

A Ti2AlNb alloy was electron beam welded, and the microstructure and mechanical behavior of the welded joints were systematically investigated. In the as-welded joint, the fusion zone (FZ) is composed of single B2/beta phase, while the heat-affected zone (HAZ) can be divided into two parts: HAZ I of B2/beta and alpha(2) phases near the fusion line and HAZ II of B2/beta, alpha(2) and O phases near the base material. The as-welded joint exhibits a similar elongation to the base material at room temperature, but fractures without obvious plasticity at 650 degrees C. Annealing the welded joint at 810 degrees C for 2 h results in precipitation of lots of fine O phase from the B2/beta matrix, due to which the mechanical performance of the welded joint is greatly improved, i.e., the elevated temperature elongation is increased to 7.3%, bringing about a synchronous rise in ultimate strength. Subjected to tensile test at room temperature, the as-welded joint generally fails along the fusion line while the as-annealed joint fails within the base material. In contrast, the fracture at elevated temperature constantly takes place in the FZ for all the joints. It is proved that electron beam welding and subsequent annealing is a promising way to link the Ti2AlNb alloy.