Laser‐Directed Energy Deposition of Ti 2 AlNb Alloy: As‐Deposited Ultrahigh Strength and Heat‐Treated Strength–Ductility Balance

ABSTRACT An ultra‐high as‐deposited tensile strength of 1408 MPa—the highest reported value for laser‐directed energy deposition (L‐DED) fabricated Ti 2 AlNb alloy—is achieved in this study. The as‐deposited microstructure consists of coarse B2 grains with a high density of fine acicular O phase precipitates within the grains, along with a brittle α 2 phase distributed at B2 grain boundaries. This yields an ultimate tensile strength (UTS) of 1408 MPa, but limited ductility due to the brittle grain‐boundary α 2 phase, with an elongation (EL) of only 0.8%. To enhance the strength–ductility synergy, a two‐step heat treatment was conducted: first, solution treatment at 960°C for 2 h followed by air cooling (AC); second, aging at 850°C for 6 h followed by AC. The heat‐treated microstructure exhibits α 2 ‐core/O‐rim structures and fine secondary O phase precipitates, with a markedly increased volume fraction of the O phase, maintaining a high strength of 1009 MPa while dramatically improving ductility to 6.1%. This work provides a pathway for tailoring L‐DED fabricated Ti 2 AlNb alloys for high‐performance aerospace applications.