Page 38 - IJAMD-2-3

International Journal of AI for
Materials and Design Biomimetic ML for AFSD aluminum properties

metal rods are employed as feedstock. These rods are differences emerged. In Cu, heat generation was
fixed to a rotating spindle that exerts a downward force, predominantly due to interfacial friction resulting from
generating frictional heat that plasticizes the material. The full slipping contact between the tool and the material.
softened material is then layered onto the substrate to form In contrast, for Al-Mg-Si, both interfacial friction and
the additive component. As the spindle moves along a plastic energy dissipation contributed to heat generation
predefined trajectory, the component takes shape. However, under partial slipping and sticking conditions. The study
the material experiences unconstrained expansion in both highlights the significance of material-specific thermal
radial and axial directions, often resulting in curled edges behavior in AFSD and provides valuable insights for
around the rod. Friction extrusion additive manufacturing optimizing solid-state additive manufacturing processes.
also employs metal rods, which are transformed into a Stubblefield et al. developed a fully coupled thermo-
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plastic state through friction with a rotating die driven by mechanical meshfree approach to simulate the AFSD
axial force. The plasticized metal is extruded from the die process, marking a significant advancement in modeling
outlet and fills the gap between the substrate and the tool, this solid-state additive manufacturing technique. Their
forming the component as the spindle moves. However, Lagrangian reference frame allowed for the tracking of
this method tends to produce poorly bonded layers due material point history and accounted for both elastic and
to the frictional interaction between the feedstock and the plastic strains. An explicit dynamics time-stepping scheme
rotating die. was implemented to handle the high non-linearity of the

AFSD, which involves a shoulder-assisted tool, typically AFSD process. The study also introduced a novel thermo-
employs rods, wires, or powders as raw materials. 6-10 These mechanical joining contact algorithm and validated the
materials are introduced into a hollow, non-consumable simulation results by comparing them with experimental
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tool and, under the combined effects of extrusion, friction, data from single-layer deposition tests. Patil et al. estimated
and stirring, become thermoplasticized and migrate key parameters such as temperature and strain rate during
downward to the substrate. Mechanical mixing between multi-layer deposition based on existing thermo-pseudo-
the softened substrate and the plasticized raw material mechanical models of friction stir processes. Their findings
creates a robust bond, after which the component is formed revealed that variations in average deposition temperature
as the spindle traverses its predefined path. Compared and strain rate significantly influenced complex material
to the other two techniques, AFSD offers more precise deformation and flash formation. Microstructural analysis
control over material flow and forming morphology. using electron backscatter diffraction showed the presence
Several essential parameters influence the AFSD process, of fine equiaxed grains along the build direction and
such as tool rotation speed, feed rate, and layer height. The finer grain bands at layer interfaces, suggesting dynamic
rate of heat generation is primarily determined by the tool’s recrystallization as the dominant restoration mechanism.
spinning speed, while feed rate or axial force governs the This grain refinement during AFSD significantly enhanced
rate of material deposition. Tool traverse velocity influences the yield strength of the deposited IN625 compared to
the spatial distribution of heat, and the layer height defines both the feed material and as-cast IN625.
the vertical distance between the tool and the substrate. AFSD has great potential in industrial applications
During the operation, material flow is driven by extrusion due to its ability to manufacture high-strength, defect-free
and shearing in the transition zone beneath the feedstock components without melting. 18-24 In the aeronautic field,
rod, with the tool’s stirring action playing an important AFSD can be applied to both repair and manufacturing
role. 11-14 Thermal evolution in AFSD is defined by heat operations for low- and high-performance parts,
generated from both friction and plastic deformation, with such as turbine blades, fuselage panels, and structural
internal temperature distribution influencing material flow. components, using materials including titanium and
Garcia et al. explored the thermal and material high-strength aluminum alloys. 25-31 The repair phase, in
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flow behavior in the AFSD process, enabling site- particular, benefits most from AFSD through localized
specific deposition of high-quality metals with refined repairs, reduced material waste, and shortened lead times.
microstructures. Their study addressed a critical gap in In the automotive industry, AFSD is increasingly used to
understanding the thermal fundamentals of AFSD by produce lightweight, high-strength components aimed at
employing in situ monitoring techniques such as infrared improving fuel efficiency and supporting sustainability.
imaging, thermocouple measurements, and optical This is largely due to its capacity to fabricate complex
imaging. Focusing on two materials – copper (Cu) and geometries in critical parts. In the defense sector, AFSD
aluminum-magnesium-silicon (Al-Mg-Si) – they observed offers the advantage of on-site manufacturing and repair
that while both materials exhibited similar thermal trends of military equipment, especially in remote or resource-
(e.g., peak temperature and cooling rate), key quantitative scarce locations. 32-37 Its capability to form gradient

Volume 2 Issue 3 (2025) 32 doi: 10.36922/ijamd.5014