Realizing deep penetration and superior mechanical properties in a titanium alloy thick plate joint via vacuum laser beam welding

Abstract

It is usually very difficult for achieving deep penetration in titanium alloy thick plates by conventional laser beam welding (LBW) under the atmospheric environment, since the laser beam energy is easily dissipated in air. In this study, LBW in a low vacuum environment (100 Pa) was proposed to realize the deep weld penetration of 16 mm of Ti–6Al–4V alloy thick plate, which was over 1 time deeper than that in the atmospheric joint (7 mm). In addition, the contents of the impurity gas elements (N, H and O) hardly changed after vacuum LBW (VLBW), ensuring the welding quality. The fusion zone mainly consisted of acicular α′ martensite, which enhanced the α′/α′ interface strengthening, resulting in the higher microhardness than that of the base material. The average tensile strength of the joint achieved 1010 MPa, with the strength efficiency 100%. Microstructure evolution mechanisms during VLBW were discussed. This study provides a reference for the engineering application of VLBW of titanium alloy thick plates.

Keywords

• Titanium alloys
• Vacuum laser beam welding
• Microstructure
• Mechanical properties