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 degrees 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 multichannel off-axis feeding for gradient material fabrication and hybrid additive manufacturing.