Microstructure and Mechanical Properties of Hot Continuous Rolling Ti-Al-Nb-Zr-Mo Titanium Alloy Seamless Tube Welded by EBW

Electron beam welding (EBW) was applied to an 8-mm-thick new type Ti-Al-Nb-Zr-Mo titanium alloy seamless tube produced by hot continuous rolling. The microstructure and mechanical properties of welded joint were investigated. Results show that the base metal (BM) consists of primary alpha, transformed beta and Widmanstatten structure. For the EBW joint, the fusion zone (FZ) consists of acicular alpha', block alpha and Widmanstatten structure, and the size of acicular alpha' decreases gradually from top to bottom of the FZ. Moreover, only primary alpha and acicular alpha' form in the heat affected zone (HAZ). The average microhardness in welded joint is ranked as follows: FZ>HAZ>BM, and the microhardness of the HAZ decreases gradually from the FZ to the BM side. The joint's tensile strength is 893 MPa and the fracture occurs at the base metal. The elongation of tensile specimens can reach 10%. The impact energy of FZ reaches similar to 80% of that of BM and the bending specimens are bended to 180 degrees without cracks.