Particle-based friction stir additive manufacturing of an Al-Mg-Mn alloy

An innovative Particle-based Friction Stir Additive Manufacturing (P-FSAM) technique has been developed, featuring a continuous off-axis feeding mechanism for metallic particles. The process optimization focuses on the ratio of actuator reciprocating frequency to tool traverse speed, ensuring adequate heat generation and particle filling for high-quality deposition. Through the implementation of an optimized stirring pin and spiral groove design, the technique facilitates Z-direction flow of thermoplastic material, resulting in enhanced interfacial bonding and material flow characteristics. This study demonstrates the successful application of P-FSAM in producing Al-5356 alloy deposits with an equiaxed fine-grained microstructure, exhibiting mechanical isotropy and a balanced combination of strength and ductility. During the stable deposition of single-pass multilayers of this alloy, P-FSAM requires about 1 kN thrust force, with a maximum steady-state temperature exceeding 435°C. The deposits exhibit refined grain structures due to dynamic recrystallization, nearly complete dissolution of the Al₃Mg₂ phase, while maintaining grain stability during thermal cycling. The deposits achieve favorable mechanical properties, with yield strength exceeding 210 MPa, ultimate tensile strength surpassing 350 MPa, and elongation over 20 % in both build and traverse directions, outperforming fusion-based additive manufacturing counterparts. P-FSAM expands the potential of solid-state additive manufacturing, paving the way for future applications involving composite particles, polymers, metal powders, and industrial scraps, as well as multi-channel off-axis feeding for gradient material fabrication and hybrid additive manufacturing.