Recent advances in metal hybrid additive manufacturing: a comprehensive review

Metal additive manufacturing (AM) holds significant potential for the rapid prototyping of complex parts in the aerospace, defense, and military industries, biomedicine, and other fields. Despite its advantages over conventional manufacturing methods, AM faces technical bottlenecks (e.g., poor densification, high residual stress, and significant anisotropy of mechanical properties), which hinder its large-scale industrial application. The newly emerging metal hybrid additive manufacturing (MHAM) serves as a viable approach to address the inherent issues associated with AM. This method integrates different auxiliary technologies (e.g., subtractive manufacturing, formative manufacturing, magnetic fields, ultrasonic fields, thermal fields, etc.), leveraging the strengths of these technologies to enhance the performance of metal components produced via AM. MHAM offers numerous advantages, such as controlling the flow of the melt pool, refining the microstructure, optimizing the grain size orientation, reducing the residual stress, enhancing the surface quality, and improving the mechanical properties and fatigue resistance. This work offers a thorough and current analysis of the state of MHAM development, including additive and subtractive hybrid manufacturing, additive and formative hybrid manufacturing, and energy field-assisted additive manufacturing. It delineates the MHAM technology framework and clarifies the interaction mechanisms among various auxiliary technologies used in AM. Additionally, it discusses the impacts of MHAM on melt pool dynamics, solidification processes, densification, microstructure evolution, surface quality, and mechanical and fatigue properties. In summary, the distinct characteristics of various MHAM techniques are outlined, and future trends in MHAM development are anticipated.