Effect of Different Laser Oscillation on the Microstructure and Defects of Additive Manufactured Al-Cu-Mg Alloys

Al-Cu-Mg alloy was fabricated using 8-shaped, infinite, circular, linear oscillation laser-directed energy deposition (O-LDED), and traditional Gaussian LDED methods. The effect of different oscillation patterns on the solidification defects and microstructural evolution of the Al-Cu-Mg alloy were investigated. The results show that circular oscillation effectively reduced porosity and promoted grain refinement and equiaxial in the microstructure of the alloy. The oscillating laser beam drove melt flow, suppressing the formation of temperature gradients and disrupting the growth of columnar grains. Compared to other oscillation patterns, circular oscillation more closely aligns with the flow regular of the melt pool, enhances Marangoni flow, inhibits the initiation and development of defects near grain boundaries, and generates numerous fragmented grains that can act as nucleation particles, thereby achieving refinement and equiaxial of grains. Circular oscillation leads to a substantial 300% increase in elongation without sacrificing the yield and tensile strength of the Al-Cu-Mg alloy. In addition, the principles of solidification crystallization of Al-Cu-Mg alloy in different laser oscillations were explored, laying the foundation for subsequent research on the O-LDEDed aluminum alloy.