A comparative study of aluminium properties manufactured using additive friction stir deposition (AFSD) and wire arc additive manufacturing (WAAM)

Abstract Wire arc additive manufacturing (WAAM) has recently gained considerable attention due to its capability to manufacture large-size metal with a length of one meter or above, with good microstructural and mechanical properties. However, the manufacture of critical components exposed to extreme environmental conditions, such as high stresses, remains the focus of most research studies. The applications of WAAM in high-tech industries, such as aerospace and marine modes, remain limited due to metallurgical challenges such as oxidation, porosity, cracking, and deformation, especially for high-strength aluminium alloys, including 6XXX and 7XXX series. The aforementioned metallurgical challenges in WAAM are minimized to some extent by another emerging technology, known as additive friction stir deposition (AFSD). AFSD is capable of manufacturing large-size and high strength (strength equal to or greater than that of the raw material) industrial components with fewer metallurgical defects and refined microstructures. However, this technology is in its developmental stage and possesses some challenges, such as oxidation, which is currently an emerging topic for researchers in metal additive manufacturing (AM). This paper reviews the potential of various additive manufacturing (AM) techniques for the manufacture of high-strength components, using either unweldable virgin or recycled high-strength aluminium alloys. The study also provides a comprehensive overview of the importance of recycling aluminium, as well as the challenges of utilizing aluminium (Al) alloys within metal AM. Considerations related to microstructure, the mechanical properties and metallurgical defects in both these technologies are extensively discussed and compared. The study concludes that both technologies are still being developed and experience various metallurgical issues, which need to be addressed to fully utilize WAAM and AFSD for critical applications. Further, the AFSD process is shown to be a better alternative to the WAAM process in the fabrication of Al components, where it possesses less metallurgical issues, higher strength and more refined microstructures. The literature suggests ultimate tensile stress (UTS) and average elongation percentage during AFSD in the range of 197.3 MPa–306 MPa and 8.6%–39% for Al alloys, respectively. However, slightly better UTS values in the range of 344 MPa–349 MPa and significant reduction in average elongation percentage to 5% is noted during WAAM process. Furthermore, AFSD exhibited significantly higher microhardness values (40.8 HV–151.4 HV) when compared to WAAM (73 HV–111 HV). Accordingly, the study notes that further numerical and experimental studies are needed to fully understand material flow in stirring zones during the AFSD process.