Surface composites by friction stir processing: A review

Friction stir welding/processing of metals and alloys: A comprehensive review on microstructural evolution

BACKGROUNDMetallic components are the cornerstone of modern industries such as aviation, aerospace, automobile manufacturing, and energy production. The stringent requirements for high-performance metallic components impede the optimization of materials selection and manufacturing. Laser-based additive manufacturing (AM) is a key strategic technology for technological innovation and industrial sustainability. As the number of applications increases, so do the scientific and technological challenges. Because laser AM has domain-by-domain (e.g., point-by-point, line-by-line, and layer-by-layer) localized forming characteristics, the requisite for printing process and performance control encompasses more than six orders of magnitude, from the microstructure (nanometer- to micrometer-scale) to macroscale structure and performance of components (millimeter- to meter-scale). The traditional route of laser-metal AM follows a typical “series mode” from design to build, resulting in a cumbersome trial-and-error methodology that creates challenges for obtaining high-performance goals.ADVANCESWe propose a holistic concept of material-structure-performance integrated additive manufacturing (MSPI-AM) to cope with the extensive challenges of AM. We define MSPI-AM as a one-step AM production of an integral metallic component by integrating multimaterial layout and innovative structures, with an aim to proactively achieve the designed high performance and multifunctionality. Driven by the performance or function to be realized, the MSPI-AM methodology enables the design of multiple materials, new structures, and corresponding printing processes in parallel and emphasizes their mutual compatibility, providing a systematic solution to the existing challenges for laser-metal AM. MSPI-AM is defined by two methodological ideas: “the right materials printed in the right positions” and “unique structures printed for unique functions.” The increasingly creative methods for engineering both micro- and macrostructures within single printed components have led to the use of AM to produce more complicated structures with multimaterials. It is now feasible to design and print multimaterial components with spatially varying microstructures and properties (e.g., nanocomposites, in situ composites, and gradient materials), further enabling the integration of functional structures with electronics within the volume of a laser-printed monolithic part. These complicated structures (e.g., integral topology optimization structures, biomimetic structures learned from nature, and multiscale hierarchical lattice or cellular structures) have led to breakthroughs in both mechanical performance and physical/chemical functionality. Proactive realization of high performance and multifunctionality requires cross-scale coordination mechanisms (i.e., from the nano/microscale to the macroscale).OUTLOOKOur MSPI-AM continues to develop into a practical methodology that contributes to the high performance and multifunctionality goals of AM. Many opportunities exist to enhance MSPI-AM. MSPI-AM relies on a more digitized material and structure development and printing, which could be accomplished by considering different paradigms for AM materials discovery with the Materials Genome Initiative, standardization of formats for digitizing materials and structures to accelerate data aggregation, and a systematic printability database to enhance autonomous decision-making of printers. MSPI-oriented AM becomes more intelligent in processes and production, with the integration of intelligent detection, sensing and monitoring, big-data statistics and analytics, machine learning, and digital twins. MSPI-AM further calls for more hybrid approaches to yield the final high-performance/multifunctional achievements, with more versatile materials selection and more comprehensive integration of virtual manufacturing and real production to navigate more complex printing. We hope that MSPI-AM can become a key strategy for the sustainable development of AM technologies. Download high-res image Open in new tab Download PowerpointMaterial-structure-performance integrated additive manufacturing (MSPI-AM).Versatile designed materials and innovative structures are simultaneously printed within an integral metallic component to yield high performance and multifunctionality, integrating in parallel the core elements of material, structure, process, and performance and a large number of related coupling elements and future potential elements to enhance the multifunctionality of printed components and the maturity and sustainability of laser AM technologies.

Material-structure-performance integrated laser-metal additive manufacturing.

Mechanical behavior of high-entropy alloys

Friction stir based welding and processing technologies - processes, parameters, microstructures and applications: A review

The spatial gradients in microstructure have been proven to be effective in optimizing the performance of components, and several techniques have been developed to achieve this microstructure. Nevertheless, the local microstructural modification methods inevitably result in the formation of gradient microstructure leading to a variation in the property. This work systematically investigates the effect of gradient microstructure formed during thick section friction stir weld AA 5083 alloy on its mechanical properties. A novel macro-indentation technique, profilometer-based indentation plastometry (PIP), is utilized to capture the variation in the mechanical properties in the feedstock (rolled plate) and weld region. The feedstock exhibited a gradient microstructure owing to different stress states during rolling. Additionally, the stirring of the tool resulted in a complex material flow pattern producing a microstructure gradient in the weld region. The aspect ratio of the grains was identified as the primary factor causing variation in indentation response in the feedstock. In contrast, variation in the grain size in the weld region resulted in property variation. Overall, the stir zone has a lower yield strength (158 ± 4 MPa) than the base material (173 ± 3 MPa). In addition, microstructure heterogeneity in the stir zone resulted in lower elongation than the base material. 

Macroscale property assessment and indentation characteristics of thick section friction stir welded AA 5083

Metals are excellent conductors for phonon transportation such as vibration, sound, and heat. Generally, metal sound insulators require multi-material structure or defects, and uni-metal sound insulators have been challenging. Therefore, we propose a design of a defect-free sound insulator made by single-alloy with multiple friction stir processes (FSP). Periodic friction stir processing can induce superlattice-liked local mechanical properties modifications. By experimental acoustic characterization, we observe that FSP can introduce clear acoustic-elastic property contrast on an aluminum plate by the presence of stir zone and heat-affected zones. In numerical simulations, the signature FSP-induced property profile was periodically and parallel arranged on a long aluminum plate. The transmission gap frequencies are present on the frequency spectrum with the sound propagation direction perpendicular to the FSP paths. We further introduce disorder offsets on the FSP periodicity. Anderson localization is found on a resonance frequency, which provides -11dB sound reduction by an exponential decay. Due to the finite design length, the slight disorder can also enhance sound insulation in the periodic transmission gap frequency. With analysis and comparison with different configurations, the best performance in the models can achieve -30dB sound insulation in around 350 mm long aluminum alloy plate with 14 parallel FSPs. This article is protected by copyright. All rights reserved. 

Defect‐Free Sound Insulator Using Single Metal‐Based Friction Stir Process Array

Meshfree Simulation and Analysis of Contact Conditions and Microstructure Evolution in Shear Assisted Processing and Extrusion

Lumped parameter methods aim to simplify the evolution of spatially-extended or continuous physical systems to that of a"lumped"element representative of the physical scales of the modeled system. For systems where the definition of a lumped element or its associated physics may be unknown, modeling tasks may be restricted to full-fidelity simulations of the physics of a system. In this work, we consider data-driven modeling tasks with limited point-wise measurements of otherwise continuous systems. We build upon the notion of the Universal Differential Equation (UDE) to construct data-driven models for reducing dynamics to that of a lumped parameter and inferring its properties. The flexibility of UDEs allow for composing various known physical priors suitable for application-specific modeling tasks, including lumped parameter methods. The motivating example for this work is the plunge and dwell stages for friction-stir welding; specifically, (i) mapping power input into the tool to a point-measurement of temperature and (ii) using this learned mapping for process control.

Neural Lumped Parameter Differential Equations with Application in Friction-Stir Processing

The dynamic behavior and energy transformation mechanism of the multi-period evolution of bubbles collapsing near a wall have been essential considerations in bubble dynamics research. In this study, a compressible two-phase solver considering thermodynamics and phase transitions is developed on OpenFOAM (version v2112). This model is validated via comparison with analytical solutions and experimental results. The dynamics of the multi-period evolution of bubbles collapse process at different dimensionless stand-off distances (γ) were accurately reproduced. The results indicate that the shock wave emitted by the collapse of cavitation bubbles impacts the wall, causing the fluid temperature along the wall to increase. Moreover, the liquid jet has a dual effect on the wall temperature increase, depending on the initial stand-off distance between the bubble and the wall. When γ is small, the jet carries the low-temperature fluid to occupy the high-temperature region, and when γ is large, the jet carries the high-temperature fluid to occupy the low-temperature region. Compared with the mechanisms above of wall temperature increase, the collapse process of cavitation, when directly attached to the wall, increases the fluid temperature along the wall more significantly. Additionally, an energy transformation mechanism is proposed considering the internal bubble energy based on the analysis of the internal bubble energy and acoustic radiation energy with different γ values. Both the internal and acoustic radiation energy initially decreased and subsequently increased with increasing γ values. These findings provide deeper insights into the near-wall collapsing cavitation process mechanism.

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Thermodynamic Behavior and Energy Transformation Mechanism of the Multi-Period Evolution of Cavitation Bubbles Collapsing near a Rigid Wall: A Numerical Study

Tianhao Wang

Papers

Macroscale property assessment and indentation characteristics of thick section friction stir welded AA 5083

Defect‐Free Sound Insulator Using Single Metal‐Based Friction Stir Process Array

Meshfree Simulation and Analysis of Contact Conditions and Microstructure Evolution in Shear Assisted Processing and Extrusion

Neural Lumped Parameter Differential Equations with Application in Friction-Stir Processing

Thermodynamic Behavior and Energy Transformation Mechanism of the Multi-Period Evolution of Cavitation Bubbles Collapsing near a Rigid Wall: A Numerical Study