Fabrication challenges and mechanical properties of SiC-reinforced Al-7075 laminates synthesized via friction stir additive manufacturing: A preliminary study

Incorporating SiC nanoparticles into Al-7075 laminates offers significant potential to enhance mechanical performance; however, fabricating defect-free metal matrix laminates remains challenging due to issues such as tool wear, pin breakage, incomplete capping, tunnel defects, and non-uniform particle dispersion. In this study, Al-7075-T651/SiC laminates were fabricated via Friction Stir Additive Manufacturing (FSAM) with varying SiC contents (5–20 vol%) at a tool rotation speed of 1000 rpm and a transverse speed of 30 mm/min to establish the optimal reinforcement fraction. A two-plate laminate containing nominal 5 vol% SiC exhibited improved consolidation and comparatively fewer defects, whereas higher reinforcement fractions led to increased material flow resistance, tunnel defects, and severe tool wear resulting in pin breakage. Based on these findings, an eight-layered SiC reinforced laminate was fabricated. Microstructural analysis revealed uniform particle distribution, fine equiaxed grains, and a 98% reduction in grain size compared to the base material (BM), confirming effective dynamic recrystallization. Both the microstructure and mechanical properties exhibited non-uniform behavior along the building direction. The microhardness gradually increased from 90 to 135 HV, and the ultimate tensile strength (UTS) increased from 200.12 to 257.24 MPa. The enhanced performance of the top layers was attributed to finer grains, improved particle dispersion, and reduced defect density. Overall, both microhardness and UTS remained significantly below those of the BM, highlighting the current performance limitations of the FSAM laminates. Building on the outcomes of this preliminary study, further investigation of tool geometry, reinforcement incorporation strategies, and processing conditions is necessary to improve defect control and reinforcement uniformity. The present findings demonstrate initial process feasibility and highlight key challenges that must be addressed before structural-grade applications can be considered.