Additive manufacturing has revolutionised the production of functional components and assemblies, offering a high degree of manufacturing flexibility. This review explores the latest advancements in additive manufacturing, focusing on its fusion-based and solid-state based technologies, and highlights the use of recycled aluminium as feedstock in these processes. The advantages and limitations of incorporating recycled materials are thoroughly analysed, considering factors such as material properties, sustainability, and process acceptance. While up to 14.4 kg CO₂ per kg of aluminium is released during primary aluminium ingot production, solid-state based additive manufacturing, which is tolerant of feedstock contamination, can directly recycle aluminium. Meanwhile, fusion based additive manufacturing can readily utilise recycling pathways such as maintaining grade, upcycling, and downcycling, as well as powder reuse, providing opportunities for significant emissions reduction. The examination of feedstock manufacturing in this review, such as wire for WAAM and powder for PBF, indicates that this step indirectly increases the resource consumption of additive manufacturing. Finally, the alignment of aluminium recycling and additive manufacturing with Circular Economy principles and the UN's sustainable development goals are addressed, highlighting contributions to SDGs 3, 9, and 12.

Additive friction stir deposition (AFSD) is an emerging solid-state additive manufacturing process with a high deposition rate. Being a non-fusion additive manufacturing (AM) process, it significantly eliminates problems related to melting such as cracking or high residual stresses. Therefore, it is possible to process reactive materials or high-strength alloys with high susceptibility to cracking. Although the residual stresses are lower in this process than with the other AM processes, depending on the deposition path, geometry, and boundary conditions, residual stresses may lead to undesired deformations and deteriorate the dimensional accuracy. Thermal cycling during layer deposition, which also depends on the geometry of the manufactured component, is expected to affect mechanical properties. To this day, the influence of the deposit geometry on the residual stresses and mechanical properties is not well understood, which presents a barrier for industry uptake of this process for large-scale part manufacturing. In this study, a stepped structure with 4, 7, and 10 passes manufactured via AFSD is used to investigate changes in microstructure, residual stress, and mechanical property as a function of the number of passes. The microstructure and defects are assessed using scanning electron microscopy and electron backscatter diffraction. Hardness maps for each step are created. The residual stress distributions at the centreline of each step are acquired via non-destructive neutron diffraction. The valuable insights presented here are essential for the successful utilisation of AFSD in industrial applications.

Many industries such as aerospace, power generation, and ground transportation demand structural materials with high specific strength at elevated temperatures. Up until now, many types of heat‐resistant materials including Ni‐based superalloys, intermetallic compounds, and dispersion‐strengthened alloys have been developed for specific applications in these industries. Moreover, with the recent development of additive manufacturing techniques, these industries can now benefit from the rapid prototyping abilities, geometric freedom, and increased mechanical properties that can be achieved through various additive manufacturing processes. With this in mind, the progress made in additive manufacturing of heat‐resistant intermetallic compounds and ceramic dispersion alloys is herein examined. A brief introduction is provided on the target industries, applications, and the compositions of heat‐resistant alloys of current research interest. Then, recent research on heat‐resistant intermetallic compounds and ceramic dispersion alloys fabricated by additive manufacturing processes such as laser powder bed fusion, laser direct energy deposition, and electron‐beam powder bed fusion are reviewed with information provided on microstructure, processing parameters, strengthening mechanisms, and mechanical properties. Finally, an outlook is provided with future research suggestions.