Research progress on the regulation of molten pool dynamics, microstructure and properties of ultrasonic field assisted laser additive manufacturing

As an efficient multi-physics field assisted technology, ultrasonic laser additive manufacturing (U-LAM) achieves its core innovation through the synergistic integration of high-energy lasers and high-frequency mechanical vibrations. This coupled energy field effect effectively overcomes technical bottlenecks in conventional laser additive manufacturing, such as coarse grain structures, pronounced anisotropy, and susceptibility to defects like porosity and cracks, offering a transformative solution for fabricating high-performance metallic components. This review systematically summarizes research advances in U-LAM regarding ultrasonic application methods, key process parameters, molten pool dynamic behavior, microstructural evolution patterns, and material property enhancement. Through mechanisms of acoustic cavitation, acoustic streaming, and thermal effects, the ultrasonic energy field significantly alters the thermo-mechanical coupling conditions within the molten pool, not only refining solidification microstructures and promoting the columnar-to-equiaxed transition (CET), but also effectively suppressing pore formation and hot cracking. Additionally, ultrasonic vibrations improve interface bonding and comprehensive performance in metal matrix composites by regulating the movement and distribution of reinforcing particles. Finally, current technical challenges are summarized, and future development trends are discussed, aiming to provide systematic theoretical references and practical guidance for advancing this technology toward deeper development and industrial applications.