Search Results (48)

Additive friction stir deposition (AFSD) is a novel friction stir technology. It is one of the most prolific solid-state metal deposition processes. In recent years, the aerospace and defense industries have increased their investment in the deposition of 7xxx aluminum alloys. This has allowed AFSDs of 7xxx aluminum to move from a laboratory environment to being tested in an industrial setting. This work strives to help move the AFSD of AA7075 toward an effective production environment by providing an initial characterization of the graphite-free layer interface. To the authors’ knowledge, this is the first graphite-free study to utilize both knub–scroll and scroll tools in AA7075. It is also the first study to compare how flat, knub, knub–scroll, and scroll influence layer mixing in graphite-free AA7075. The condition of the layer interface is particularly important to build direction properties. As many end users of AFSD desire isotropic properties, improving build direction properties is extremely important. This work looks at how external tool geometries and layer height impact the layer interface. The objective is to not only better characterize the layer interface but also to determine if a specific external geometry and or layer height could help facilitate a stronger layer interface. It was found that depositions made by the knub tool at a 2.5 mm layer height generated the most visually consolidated layer interface at an optical and SEM level. Under EDS analysis, the knub tool only saw a 12% variation between peak and background oxygen counts. EBSD scans also revealed a more consistent grain size distribution. Full article

Additive friction stir deposition (AFSD) enables solid-state, layer-by-layer metal deposition, minimizing defects and elemental loss from melting. Consequently, AFSD is highly effective for manufacturing aluminum alloys. Systematic studies indicate that grain structure influences properties along different processing directions in AFSD aluminum alloys. Accordingly, this study used AFSD to fabricate an aluminum alloy wall and rigorously characterized its microstructure and mechanical properties in both the XOY plane (X direction) specimen and the YOZ plane (Z direction) specimen. Results demonstrate that AFSD-fabricated 6061 aluminum alloys exhibit refined grains. Microhardness tests revealed directional variation, with the YOZ plane (Z direction) specimens showing lower hardness. Tensile tests showed that the transverse direction (X direction) specimens had slightly higher tensile strength than the deposition direction (Z direction) specimens. This study offers theoretical guidance for optimizing AFSD metal fabrication and provides data supporting the broader adoption of AFSD-fabricated 6061 aluminum alloys. Full article

Additive friction stir deposition (AFSD) is a solid-state AM method that feeds, plasticizes, and deposits solid bars using frictional heat. Although the AFSD is a promising method, its limited technology readiness level precludes its wider use. The use of optimum process parameters is critical for achieving successful results, and closed-loop control of process parameters can improve quality even further by reacting to and resolving any unanticipated issues that arise during the process. This article investigates the utilization of a process monitoring setup including various sensors to examine temperatures, forces, vibrations, and sound during the AFSD of the Al6061 aluminum alloy. Furthermore, it benchmarks the outcomes of the same process’ parameter set with or without utilizing a proportional–integral–derivative (PID). Large thermal gradients were observed at various locations of the deposit. Significant fluctuations in temperature and force were demonstrated for the initial layers until stability was reached as the height of the deposit increased. It has been shown that the change in the process parameters may lead to undesired results and can alter the deposit shape. Finally, residual stresses were investigated using the contour measurement technique, which revealed compressive stresses at the core of the part and tensile stresses in the outer regions. Full article

Using additive friction stir deposition (AFSD), the poor weldability of 1045 steel can be solved, facilitating the efficient and high-performance additive manufacturing of its components. This study selected spherical 1045 steel powder and investigated key factors influencing mechanical properties, including deposition temperature, tool rotational rate, and axial force. The results showed that dynamic recrystallization (DRX) occurred in AFSD 1045 steel, which produced randomly oriented fine equiaxed grains with a size range of 1–3 µm and was sensitive to changes in tool rotational rate and axial force. The AFSD 1045 steel, with a maximum surface hardness of 477.2 HV, ultimate tensile strength of 1061.9–1172.3 MPa, and elongation of 8.6–19.0%, has superior overall mechanical properties compared with other forming processes. Moreover, by analyzing tensile fracture morphology, geometrically necessary dislocation (GND) density, and coincidence site lattice (CSL) boundary distribution characteristics, the strengthening mechanism in AFSD 1045 steel was discussed. The research findings serve as a reference for optimizing the AFSD process for 1045 steel and supply a new alternative for joining and manufacturing this material. Full article

The direct energy deposition arc process is widely used for fabricating medium and large components with moderate geometric complexity but often results in coarse microstructures and inconsistent hardness. This study introduces a hybrid manufacturing approach combining the friction stir burnishing process with the direct energy deposition arc by a gas–metal arc welding technique to refine the microstructure and enhance the microhardness of components fabricated from austenitic stainless steel 316L. Our former study used an aluminum alloy (A5052) friction stir burnishing tool, demonstrating significant microhardness improvement and grain refinement. However, it also faced notable challenges under high-heat and -friction conditions, including the effect of material adherence to the workpiece during processing. Therefore, this study introduces a newly developed friction stir burnishing tool made from copper (C1100) and compares its performance with the aluminum alloy tool regarding microhardness enhancement and microstructure refinement. The results indicate that the specimen processed by direct energy deposition arc combined with the copper friction stir burnishing tool demonstrated the best overall performance in grain refinement and hardness enhancement. Specifically, it achieved the highest average microhardness of 250 HV at 50 µm depths, compared to 240 HV for the aluminum alloy tool. The statistical analysis showed that both tools led to significant improvements over specimens processed without them. The statistical analysis confirmed a notable reduction in secondary dendrite arm spacing across all depths, with the copper tool demonstrating the most refinement. Additionally, a preliminary investigation of corrosion behavior revealed tool-dependent differences. Overall, this study offers a promising approach to improving additive manufacturing, particularly for industries with less stringent surface finish requirements. It could potentially reduce post-processing time and cost. Future research should explore different process parameters and assess long-term corrosion performance to develop this hybrid technique further. Full article

In this work, the effects of tool bias as a processing parameter on an additive friction stir deposition repair of AA7050-T7451 plates were investigated. In this study, the asymmetrical material flow effect was assessed by subjecting a machined groove plate to different tool biases during the AFSD process. The tool bias effectiveness on repairs was quantified through mechanical testing and destructive and non-destructive evaluation. Monotonic tensile tests conducted in parallel with a digital image correlation method captured the mechanical performance of the repairs and the local strain effects of the heat-affected zone. X-ray computed tomography images of the different tool bias repairs were analyzed for any voids or defects to measure the overall bonding effectiveness. The results suggest that the advancing side tool bias had adequate bonding with the substrate, which yielded improved mechanical performance compared to the centered and retreating side depositions. Full article

This study investigates the feasibility of using friction stir extrusion (FSE) recycled aluminum wires as filler metals for gas tungsten arc welding (GTAW) and additive manufacturing applications. A NC-controlled GTAW feeding system was developed to enable the deposition of these recycled wires. The effect of cleaning the machining chips before the FSE process on the quality of the manufactured wires and the resulting welded beads was evaluated. Wires produced from uncleaned chips and cleaned chips were compared in terms of their external appearance, ductility, and the presence of porosity after the weld deposition. The results showed that cleaning the chips before the FSE process is crucial for obtaining more uniform wires with better ductility. Automatic GTAW deposition using cleaned wires resulted in significantly improved bead geometry, reduced external porosity, and overall better quality compared to uncleaned wires. However, both wire types exhibited internal porosity, with uncleaned wires showing the worst performance. The findings demonstrate the potential of using FSE recycled aluminum wires for welding and additive manufacturing while highlighting the importance of chip cleaning and the need for further optimization to minimize porosity in the deposited material. Full article

High-entropy alloys (HEAs) have drawn substantial attention on account of their outstanding properties. Additive manufacturing (AM), which has emerged as a successful approach for fabricating metallic materials, allows for the production of complex components based on three-dimensional (3D) computer-aided design (CAD) models. This paper reviews the advancements in the AM of HEAs, encompassing a variety of AM techniques, including selective laser melting (SLM), selective laser sintering (SLS), selective electron beam melting (SEBM), directed energy deposition (DED), binder jetting (BJT), direct ink writing (DIW), and additive friction stir deposition (AFSD). Additionally, the study discusses the powders and wires utilized in AM, the post-processing of AM-processed HEAs, as well as the mechanical and corrosion properties of these alloys. The unique ultra-fine and non-equilibrium microstructures achieved through AM result in superior mechanical properties of HEAs, like improved strength and ductility. However, research regarding certain aspects of HEA AM, such as fatigue properties and creep deformation behavior, is still relatively scarce. Future research should focus on overcoming the existing limitations and exploring the potential of HEAs in various applications. Full article

The fabrication of multi-layer alloys by additive friction stir deposition (AFSD) results in a complicated microstructure and mechanical property evolution due to the repeated thermal inputs impacting the existing deposited layers. This work systematically studied the microstructure and mechanical properties of several areas (last layers, intermediate layers, and first layers) of a 16-layer 2195 alloy component fabricated by AFSD to ascertain the effect of repeated thermal cycling. The periodic heat input resulted in the minimal quantities of T₁-phase only appearing in the last layers of the sample, while the θ′-phase developed a complex precipitate with the δ′ and β′ phases. The mechanical properties of the 2195 sample exhibit a gradient development related to the microstructure, with a decrease in strength and hardness from top to bottom. The samples located in the last layers show the highest microhardness of 117.0 Hv, yield strength of 296.6 MPa, ultimate tensile strength of 440.6 MPa, and elongation of 27.1%, respectively. Full article

The material flow behavior during friction stir welding (FSW) plays a critical role in the quality of final joints. In this study, the FSW of LAZ931 duplex Mg alloy was carried out at a rotation speed of 800 rpm and welding speeds of 50, 100, and 200 mm/min, respectively. A thin pure Mg strip inserted at the interface between the two Mg-Li alloy plates was used as a marker to study the flow behavior of the materials in the FSW process. Sound welds with no defects were obtained for all three welding speeds. The microstructural evaluations along the marker on the horizontal cross-section around the keyhole of the welds were characterized. As the welding speed increased, the marker came closer to the keyhole, indicating the decreased extent of the plastic deformation of the material. In the shoulder-affected zone (SAZ), the thickness of the marker reduced gradually in the accelerating stage and finally accumulated together in the decelerating stage. However, in the pin-affected zone (PAZ), the thickness of the marker reduced sharply in the accelerating stage and then became dispersed in the decelerating stage, and the degree of dispersion decreased as the weld speed increased. As a result, an elongated grain structure was formed in the SAZ, while two equiaxial grain structures were formed in the PAZ. The material on the advancing side was refined by the pin and deposited in the weld to form a fine equiaxial grain structure due to the high strain rate. In contrast, the material on the retreating side was pushed by the pin and thus directly deposited in the weld to form a coarse equiaxial grain structure. In addition, the area of the fine equiaxial grain structure was reduced obviously with the increase in welding speed. Full article

Emerging solid-state additive manufacturing (AM) technologies have recently garnered significant interest because they can prevent the defects that other metal AM processes may have due to sintering or melting. Additive friction stir deposition (AFSD), also known as MELD, is a solid-state AM technology that utilises bar feedstocks as the input material and frictional–deformational heat as the energy source. AFSD offers high deposition rates and is a promising technique for achieving defect-free material properties like wrought aluminium, magnesium, steel, and titanium alloys. While it offers benefits in terms of productivity and material properties, its low technology readiness level prevents widespread adoption. Academics and engineers are conducting research across various subfields to better understand the process parameters, material properties, process monitoring, and modelling of the AFSD technology. Yet, it is also crucial to compile and compare the research findings from past studies on this new technology to gain a comprehensive understanding and pinpoint future research paths. This paper aims to present a comprehensive review of AFSD focusing on process parameters, material properties, monitoring, and modelling. In addition to examining data from existing studies, this paper identifies areas where research is lacking and suggests paths for future research efforts. Full article

Additive friction stir deposition (AFSD) is a novel solid-state additive manufacturing method developed on the principle of stirring friction. Benefits from its solid-phase properties, compared with traditional additive manufacturing based on melting–solidification cycles, AFSD solves the problems of porosity, cracks, and residual stress caused by the melting–solidification process, and has a significant improvement in efficiency. In AFSD, the interaction between feedstocks and high-speed rotating print heads suffers severe plastic deformation at high temperatures below the melting point, ending up in fine, equiaxed recrystallized grains. The above characteristics make components by AFSD show similar mechanical behaviors to the forged ones. This article reviews the development of AFSD technology, elaborates on the basic principles, compares the macroscopic formability and material flow behavior of AFSD processes using different types of feedstocks, summarizes the microstructure and mechanical properties obtained from the AFSD of alloys with different compositions, and finally provides an outlook on the development trends, opportunities, and challenges to the researchers and industrial fields concerning AFSD. Full article

Additive friction stir deposition (AFS-D) is considered a productive method of additive manufacturing (AM) due to its ability to produce dense mechanical parts at a faster deposition rate compared to other AM methods. Al6061 alloy finds extensive application in aerospace and nuclear engineering; nevertheless, exposure to radiation or high-energy particles over time tends to deteriorate their mechanical performance. However, the effect of radiation on the components manufactured using the AFS-D method is still unexamined. In this work, samples from the as-fabricated Al6061 alloy, by AFS-D, and the Al6061 feedstock rod were irradiated with He+ ions to 10 dpa at ambient temperature. The microstructural and mechanical changes induced by irradiation of He+ were examined using a scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and nanoindentation. This study demonstrates that, at 10 dpa of irradiation damage, the feedstock Al6061 produced a bigger size of He bubbles than the AFS-D Al6061. Nanoindentation analysis revealed that both the feedstock Al6061 and AFS-D Al6061 samples have experienced radiation-induced hardening. These studies provide a valuable understanding of the microstructural and mechanical performance of AFS-D materials in radiation environments, offering essential data for the selection of materials and processing methods for potential application in aerospace and nuclear engineering. Full article

Additive friction stir deposition (AFSD) is a solid-state metal additive manufacturing technique, which utilizes frictional heating and plastic deformation to create large deposits and parts. Much like its cousin processes, friction stir welding and friction stir processing, AFSD has seen the most compatibility and use with lower-temperature metals, such as aluminum; however, there is growing interest in higher-temperature materials, such as titanium and steel alloys. In this work, we explore the deposition of an ultrahigh-temperature refractory material, specifically, a tantalum–tungsten (TaW) alloy. The solid-state nature of AFSD means refractory process temperatures are significantly lower than those for melt-based additive manufacturing techniques; however, they still pose difficult challenges, especially in regards to AFSD tooling. In this study, we perform initial deposition trials of TaW using twin-rod-style AFSD with a high-temperature tungsten–rhenium-based tool. Many challenges arise because of the high temperatures of the process and high mechanical demand on AFSD machine hardware to process the strong refractory alloy. Despite these challenges, successful deposits of the material were produced and characterized. Mechanical testing of the deposited material shows improved yield strength over that of the annealed reference material, and this strengthening is mostly attributed to the refined recrystallized microstructure typical of AFSD. These findings highlight the opportunities and challenges associated with ultrahigh-temperature AFSD, as well as provide some of the first published insights into twin-rod-style AFSD process behaviors. Full article

Magnesium alloys, renowned for their lightweight yet high-strength characteristics, with exceptional mechanical properties, are highly coveted for numerous applications. The emergence of magnesium alloy additive manufacturing (Mg AM) has further propelled their popularity, offering advantages such as unparalleled precision, swift production rates, enhanced design freedom, and optimized material utilization. This technology holds immense potential in fabricating intricate geometries, complex internal structures, and performance-tailored microstructures, enabling groundbreaking applications. In this paper, we delve into the core processes and pivotal influencing factors of the current techniques employed in Mg AM, including selective laser melting (SLM), electron beam melting (EBM), wire arc additive manufacturing (WAAM), binder jetting (BJ), friction stir additive manufacturing (FSAM), and indirect additive manufacturing (I-AM). Laser powder bed fusion (LPBF) excels in precision but is limited by a low deposition rate and chamber size; WAAM offers cost-effectiveness, high efficiency, and scalability for large components; BJ enables precise material deposition for customized parts with environmental benefits; FSAM achieves fine grain sizes, low defect rates, and potential for precision products; and I-AM boasts a high build rate and industrial adaptability but is less studied recently. This paper attempts to explore the possibilities and challenges for future research in AM. Among them, two issues are how to mix different AM applications and how to use the integration of Internet technologies, machine learning, and process modeling with AM, which are innovative breakthroughs in AM. Full article