In Situ Formation of L1 2 ‐Al 3 Ti Precipitates Enabling High Strength and Toughness in Oscillating Laser‐Welded Aluminum Alloy

A synergistic strategy combining a Ti interlayer and circular beam oscillation was proposed to improve the laser weldability of 6082‐T6 aluminum alloy. The Ti interlayer suppressed porosity, eliminated columnar grains, and significantly reduced grain size by 67.7% at the weld center. Mechanistically, fine L1 2 ‐Al 3 Ti precipitates clearly showing a strong crystallographic orientation relationship with the α‐Al matrix, acted as efficient heterogeneous nucleation sites during solidification. Consequently, the ultimate tensile strength of the welded joint increased from 200 to 250 MPa, and the elongation remarkably improved by 176%. In situ computed tomography and scanning electron microscopy further revealed that Ti in situ alloying mitigated the detrimental effect of pores and enabled Al 3 Ti to function as a deformable precipitate, simultaneously enhancing the strength and ductility of the weld. This work demonstrates the formation of coherent L1 2 ‐Al 3 Ti precipitates via Ti in situ alloying and reveals a pore‐tolerant microstructure governed fracture mechanism, allowing the weld to achieve near base metal strength with excellent ductility.