Oscillating laser directed energy deposition (OLDED) has attracted considerable attention for component manufacturing owing to its outstanding influence on thermal-fluid behaviour and molten pool formation during the process. However, there remains a dearth of systematic analysis that links intricate thermodynamic behaviour with crucial process parameters, including oscillation frequency and amplitude, and a reliable evaluation of the consistency of microstructure and properties in large-scale components under constant parameters. Herein, this paper aims to systematically elucidate the influence rules of two key variables to achieve coordinated control over microstructure and properties across the entire deposition domain. The acceleration and shear forces induced by the beam oscillation generate an intense stirring effect within a confined volume, which fragments the growing dendrites more effectively. Moreover, the quasi-surface heat source characteristics imparted by beam oscillation lead to more uniform and flattened temperature gradient inside the molten pool, which significantly enlarges the constitutionally supercooled zone. This facilitates the transition from columnar to equiaxed grains and achieves complete microstructural equalization. Multilayer Ti6Al4V specimens with various oscillating amplitudes and frequencies were further fabricated using OLDED, and an average grain size of 10.33 μm could be obtained with the combination of a relatively high frequency (90 Hz) and an amplitude (0.5 mm) comparable to the laser spot diameter. The tensile strength and yield strength are approximately 1316 MPa and 1210 MPa, respectively, representing increases of 45.69% and 40.53% compared with the non-oscillation specimen. This novel additive manufacturing technology presents a novel strategy for the dependable fabrication of high-performance critical titanium alloy engineering components.
 

Laser directed energy deposition; Beam oscillation; High-performance manufacturing; Titanium alloy; Mechanical property