Izboljšanje mehanske zmogljivosti zvarnih spojev za podvodne aplikacije ter izboljšanje lastnosti intermetalne plasti zvarov na osnovi Al zlitine AA5083 in Cu

This research investigates the underwater friction stir welding (UWFSW) of dissimilar AA5083 aluminum and pure-copper plates, aiming to enhance the mechanical performance through precise control of the process parameters and the suppression of excessive intermetallic compound (IMC) formation. The UWFSW was performed using a CNC vertical milling machine under full immersion to regulate the heat input and improve the joint’s integrity. The optimized parameters yielded a maximum tensile strength of 7.5 MPa, impact strength of 7.5 J, and peak microhardness of 111 VH, outperforming conventional dry FSW joints. Optical microscopy and SEM analyses revealed a defect-free joint with a fine equiaxed grain structure in the stir zone, minimal deformation in the parent zones, and a uniform IMC layer of 2–5-µm thickness along the Al–Cu interface. The underwater cooling effect restricted grain coarsening and prevented void formation, resulting in enhanced metallurgical bonding. The study confirms that UWFSW offers a superior route to producing high-strength, corrosion-resistant Al–Cu dissimilar joints, making it highly suitable for marine, cryogenic, and high-performance electrical applications.