A Review of Solid-State Additive Manufacturing Processes

In the last few decades, massive efforts have been added to investigate liquid-state additive manufacturing (AM) processes, such as laser and electron beam-based AM, in the context of their technicality, commercial viability, and research progress. However, the challenges associated with localized melting, processing complexity, defects, high amount of equipment, and operation cost have sparked an interest in the possibility of alternative solid-state AM methods. Therefore, it is vital to consolidate the major solid-state AM processes and their advancements in a lucid manner. The aim of this paper is to provide a short review of the major solid-state mechanical deformation-based AM processes, such as ultrasonic-assisted, friction stir-deposited, and cold-sprayed AM, in the context of their research advancements, challenges, and capabilities. It has been observed that solid-state AM processes can effectively suppress the various shortcomings encountered with liquid-state AM techniques. Among the different solid-state AM methods, the additive friction stir AM techniques are outstanding, with isotropic microstructures and mechanical properties almost similar to the base metals.