Performance-control orientated hybrid metal additive manufacturing technologies: State of the art, challenges, and future trends

Metal additive manufacturing (AM) technologies have made significant progress in the basic theoretical field since their invention in the 1970s. However, performance instability during continuous processing, such as thermal history, residual stress accumulation, and columnar grain epitaxial growth, consistently hinders their broad application in standardized industrial production. To overcome these challenges, performance-control-oriented hybrid AM (HAM) technologies have been introduced. These technologies, by leveraging external auxiliary processes, aim to regulate microstructural evolution and mechanical properties during metal AM. In this context, HAM technologies for molten pool regulation and solidified material deformation are identified as energy field-assisted AM (EFed AM, e.g., ultrasonic, electromagnetic, heat, etc.) technologies and interlayer plastic deformation-assisted AM (IPDed AM, e.g., laser shock peening, rolling, ultrasonic peening, friction stir process, etc.) technologies, respectively. A detailed and systematic review of performance-control-oriented HAM technologies is then provided. This review covers the influence of external energy fields on the melting, flow, and solidification behavior of materials, and the regulatory effects of interlayer plastic deformation on grain refinement, nucleation, and recrystallization. Furthermore, the role of performance-control-oriented HAM technologies in managing residual stress conversion, metallurgical defect closure, mechanical property improvement, and anisotropy regulation is thoroughly reviewed and discussed. The review concludes with an analysis of future development trends in EFed AM and IPDed AM technologies.