Additive Friction Stir Research Articles

Experimental evaluation of T-peel strength on functionally graded Al5083 and HDPE tri-laminated composites fabricated by colding-assisted friction stir additive manufacturing

Functionally graded composites offer impressive promise in overcoming the inherent weaknesses of Metal-polymer hybrid structures. In this study, functionally graded 5083 aluminum (Al5083) and high-density polyethylene (HDPE) tri-laminated composites were fabricated by colding-assisted friction stir additive manufacturing (CA-FSAM) and friction stir additive manufacturing (FSAM). Functionally graded laminate composites have been used to overcome these drawbacks by varying the thickness of the raw laminate. The thickness changes in the user sheets were functionally 0.75 mm compared to the previous laminate. Finally, the initial sheets were transformed to three thicknesses: 3, 2.25, and 1.5 mm. The bond strength between the sheets was measured using the T-peel test. In the T-peel test, the initial crack length was 25 mm and the length of the weld zone was 111 mm. The results showed that the bond strength between the laminates improved with cooling after the CA-FSAM process. The bond strength is essentially determined by the amount of covalent bonding, which, in turn, is a function of the density on the treated surface. Dislocation forest at the surface of the tri-laminate composite can be considered a consequence of T-peel test. The joining mechanism could be ascribed to mechanical interlocking, adhesion bonding at the interface of the Al5083 alloy and HDPE polymer, and metal-chip reinforcement in HDPE of the stir zone. The maximum force (Fmax) obtained in the FSAM and CA-FSAM specimens were 1057.58 and 1254.20 N, respectively. Average force of T-peel test (Favg peel) obtained in the FSAM and CA-FSAM specimens was 984.36 and 1024.32 N, respectively.

Thermal prediction of additive friction stir deposition through Bayesian learning- enabled explainable artificial intelligence

Additive friction stir deposition is an emerging solid-state metal additive manufacturing technology that can conveniently and economically produce fully-dense, high-end components, rendering it promising for high-value manufacturing industries, such as defense, aerospace, and space. Like in other metal additive processes, the thermal characteristics in additive friction stir deposition govern the quality and properties of the printed products but is challenging to predict and control in this complex manufacturing system. Recent advances in artificial intelligence provide a powerful data-driven prediction paradigm, which nevertheless necessitates extensive training datasets and struggles to be applied across diverse material systems that exhibit significant variations in thermal and material flow characteristics during printing. Relying solely on physics-based modeling also lacks success due to potential model discrepancies, unknown material parameters, and high computational cost. Here, we propose to address these challenges by developing an explainable artificial intelligence scheme via Bayesian learning, in which the physics-based surrogate model is calibrated and updated via machine learning of in-situ monitoring data, resulting in a physics-informed, data-driven model for temperature distribution during additive friction stir deposition. The efficacy of this approach is demonstrated in printing of an Al-Mg-Si alloy, in which fast, accurate temperature prediction is achieved using a moderate number of physics simulation trials and a small number of in-situ measurements. This approach also offers physical insights into previously unknown parameters, such as the interfacial slip/stick coefficient and back heat transfer constant.

Multi-physics Approach to Predict Fatigue Behavior of High Strength Aluminum Alloy Repaired via Additive Friction Stir Deposition

A smooth particle hydrodynamic (SPH) simulation of an additive friction stir deposition (AFSD) repair was used to inform a multi-physics approach to predict the fatigue life of a high strength aluminum alloy. The AFSD process is a solid-state layer-by-layer additive manufacturing approach in which a hollow tool containing feedstock is used to deposit material. While an understanding of the evolving microstructures is necessary to predict material performance, the elevated temperatures and strain rates associated with severe plastic deformation processes (SPDP) make accurate collection of experimental data within AFSD difficult. Without the ability to experimentally determine material history within the AFSD process, an SPH model was employed to predict the thermomechanical history. The SPH simulation of an AFSD repair was used to inform several microstructural models to predict material history during and after processing with AFSD and a post-processing heat treatment. These microstructure models are then used to inform a mechanistic microstructure and performance model to predict the fatigue life of an AFSD repair in AA7075.

Closed-loop temperature controlled solid-state additive manufacturing of Ti-6Al-4V with forging standard out-of-plane tensile properties

Here, we present the first demonstration of additive friction stir deposition of Ti-6Al-4V with closed-loop temperature control, wherein the print head rotation rate is adjusted in real-time to maintain a constant tool temperature during deposition. The as-printed Ti-6Al-4V is fully dense, achieving forging standard tensile properties along both the in-plane and out-of-plane directions. The measured yield strength, ultimate tensile strength, and elongation are 903 MPa, 1000 MPa, and 17% along the in-plane direction, and 948 MPa, 1024 MPa, and 16% along the out-of-plane direction. With closed-loop temperature control, the microstructure is found to be comparable along the thickness direction, contrasting the previous work performed under parameter-controlled conditions. For all the deposition conditions explored in this work, the deposited Ti-6Al-4V exhibits a lamellar microstructure with alpha laths forming inside prior beta grains, indicating higher peak temperatures than the beta transus. The increase of a pseudo heat index leads to an increase in the prior beta grain size and a decrease of the out-of-plane yield strength. Deposition of Ti-6Al-4V is seen to modify the microstructure of the substrate near the interface: the original equiaxed microstructure is replaced by lamellar and bimodal microstructures. We finally discuss the possibility of forming equiaxed microstructures in the as-deposited Ti-6Al-4V and provide evidence for different types of microstructures forming in the same deposition layer, which may be caused by the thermal gradient during reheating.

Dynamic Tensile Behavior of Laser-Directed Energy Deposition and Additive Friction Stir-Deposited AerMet 100

Quasi-static and high-rate tensile experiments were used to examine the strain rate sensitivity of laser-directed energy deposition (L-DED)- and additive friction stir deposition (AFSD)-formed AerMet 100 ultrahigh-strength steel-additive manufactured builds. Electron backscattered diffraction (EBSD) revealed similar as-deposited grain sizes between the two AM processes at approximately 24 μm and 17 μm for the L-DED and AFSD samples, respectively. The strain hardening rate, θ, revealed little change in the overall hardening observed in the L-DED and AFSD materials, with a consistent hardening in the quasi-static samples and three identifiable regions in that of the high-rate tested materials. The L-DED deposited materials displayed average ultimate tensile strength values of 1835 and 2902 MPa for the 0.001 s−1 and 2500 s−1 strain rates, respectively and the AFSD deposited materials displayed ultimate tensile strength values of 1928 and 3080 MPa for the 0.001 s−1 and 2500 s−1 strain rates, respectively. Overall, the strength for both processes displayed a positive strain rate sensitivity, with increases in strength of ~1000 MPa for both processes. Fractography revealed significant solidification voids in the laser DED material and poor layer adhesion in the AFSD material.

Towards Understanding the Relationships between Processing Conditions and Mechanical Performance of the Additive Friction Stir Deposition Process

In this research, we explore the preliminary effects of processing conditions using a novel additive manufacturing (AM) process, known as additive friction stir deposition (AFSD), on resulting build direction (BD) mechanical performance. Using the AFSD process, a feasibility study of three AM builds of identical size are created using differentiating processing parameters. A relationship referred to as the deposition pitch, exhibiting similarities to weld pitch, is determined to be a simple but effective predictor of the interlayer bonding in AFSD processing of AA7020. The deposition pitch directly correlates the necessary temperature, time, and pressure required for effective solid-state bonding. Using this correlation, increased mechanical performance in the BD is achieved through an increase in deposition pitch. A reduction in the deposition pitch from 4.46 rev/mm to 1.08 rev/mm resulted in a significant decrease in failure strain from 24.4% to 0.82%, with the failure mechanism shifting from a ductile failure to brittle failure. The inverse relationship between grain refinement and BD failure strain at high deposition pitches suggests deposition pitch and heat input are the dominant factors in the resulting BD mechanical properties.

Microstructure and mechanical properties of Al–Li alloy manufactured by additive friction stir deposition

The microstructure and mechanical properties of 2195 Al–Li alloy manufactured by additive friction stir deposition (AFSD) were thoroughly investigated before and after various post-heat treatments. The 4-layer built sample is characterized by the distinct layer-dependent microstructure, i.e., the grain size, texture, and precipitate, and resultant heterogenous mechanical properties, owing to the layer-dependent thermal histories of each layer. Post-heat treatments can significantly improve the mechanical strength and reduce the layer-dependent mechanical properties, via introducing the nanosized T1-phase. The AFSD Al–Li alloy after solution treatment and artificial aging achieved the max YS of 491.1 MPa and max UTS of 505.0 MPa. However, the ductility of the alloy is concomitantly reduced by the presence of precipitate free zones (PFZ) along grain boundaries after post-heat treatments. For the bottom layers, EL of AFSD-A and AFSD-ST-A samples are decreased by 65.3% and 76.2%, respectively, compared to AFSD.

Dynamic Behavior Characterization of Aluminum Alloy 7020 Manufactured Using the Additive Friction Stir Deposition Process

Dynamic Behavior Characterization of Aluminum Alloy 7020 Manufactured Using the Additive Friction Stir Deposition Process

Additive Friction Stir Deposition of AA7075-T6 Alloy: Impact of Process Parameters on the Microstructures and Properties of the Continuously Deposited Multilayered Parts

In the aircraft industry, the high-strength aluminum alloys AA7075 and AA2024 are extensively used for the manufacture of structural parts like stringers and skins, respectively. Additive manufacturing (AM) of the AA7075-T6 aluminum alloy via friction stir deposition to build continuously multilayered parts on a substrate of AA2024-T4 aluminum has not been attempted so far. Accordingly, the present work aimed to explore the applicability of building multilayers of AA7075-T6 alloy on a substrate sheet of AA2024-T4 alloy via the additive friction stir deposition (AFSD) technique and to optimize the deposition process parameters. The experiments were conducted over a wide range of feed rates (1–5 mm/min) and rotation speeds (200–1000 rpm). The axial deposition force and the thermal cycle were recorded. The heat input to achieve the AFSD was calculated. The AA7075 AFSD products were evaluated visually on the macroscale. The microstructures were also investigated utilizing an optical microscope and scanning electron microscope (SEM) equipped with an advanced EDS technique. As well as the presence phases, the mechanical performance of the deposited materials in terms of hardness and compressive strength was also examined. The results showed that the efficiency of the deposition process was closely related to the amount of heat generated, which was governed by the feeding rate, the rotational speed, and the downward force. AA7075 defect-free continuously multilayered parts were produced without any discontinuity defects at the interface with the substrate at deposition conditions of 1, 2, 3, and 4 mm/min and a constant 400 rpm consumable rod rotation speed (CRRS). The additively deposited AA7075-T6 layers exhibited a refined grain structure and uniformly distributed fragment precipitates compared to the base material (BM). The gain size decreased from 25 µm ± 4 for the AA7075-T6 BM to 1.75 µm ± 0.41 and 3.75 µm ± 0.78 for the AFSD materials fabricated at 1 and 4 mm/min deposition feeding rates, respectively, at 400 rpm/min. Among the feeding rates used, the 3 mm/min and 400 rpm rod rotation speed produced an AA7075 deposited part possessing the highest average hardness of 165 HV ± 5 and a compressive strength of 1320 MPa.

Influence of Preheating Temperature on the Microstructure and Mechanical Properties of 6061/TA1 Composite Plates Fabricated by AFSD.

In this study, composite plates of 6061/TA1 were successfully manufactured using additive friction stir deposition (AFSD). The impact of preheating temperatures (room temperature, 100 °C, 200 °C) on the interfacial microstructure and interface mechanical properties at various deposition zones was studied. The results showed that as the preheating temperature increased or when the deposit zone shifted from the boundary to the center, the diffusion width of Al and Ti increased, accompanied by an increase in bonding shear strength. Moreover, in the boundary zone of the sample preheated at room temperature (P-RT), only mechanical bonding was observed, resulting in the lowest bonding shear strength. Conversely, the other samples exhibited a combination of mechanical and metallurgical bonding. Under the preheating temperature of 200 °C, interfacial intermetallic compounds were observed near the center zone, which exhibited the highest bonding shear strength.

Potential and challenges for large-scale near-net-shaping of 7xxx aerospace grade aluminum via additive friction stir deposition

This letter examines the potential and challenges of using additive friction stir deposition for large-scale near-net-shaping of 7xxx Al alloys, particularly AA7075 and AA7050. Compared to fusion-based additive manufacturing, which is unable to print these alloys without feedstock modification or composition change, additive friction stir deposition is an emerging solid-state additive process with a thermomechanical processing nature that can render fully-dense AA7075 and AA7050 in the as-deposited state. More importantly, wrought-like tensile properties have been demonstrated in the deposited AA7075 based on the original composition. The process is well-suited for large-scale printing due to its high build rate and scalability. Significant challenges nevertheless exist in process and post-process control, in addition to the impurity from lubrication.

Tailoring microstructure of additive friction stir-deposited Al–Mg alloy through post-processing deformation treatment for enhancing mechanical performance

This study explored the influence of the amount of post-processing deformation on the microstructure and mechanical properties of Al-5083 fabricated by the additive friction stir deposition (AFSD) process. The findings indicated that, through post-processing deformation treatment, the tensile properties achieved were comparable to those of wrought 6061-T6 Al alloy.

A Novel Approach for Enhanced Mechanical Properties in Solid-State Additive Manufacturing by Additive Friction Stir Deposition Using Thermally Stable Al-Ce-Mg Alloy

A Novel Approach for Enhanced Mechanical Properties in Solid-State Additive Manufacturing by Additive Friction Stir Deposition Using Thermally Stable Al-Ce-Mg Alloy

Microstructure Evolution and Mechanical Properties of Single-Layer Multipass Overlapped Al-Mg-Mn-Sc-Zr Alloy Fabricated via Additive Friction Stir Deposition

Microstructure Evolution and Mechanical Properties of Single-Layer Multipass Overlapped Al-Mg-Mn-Sc-Zr Alloy Fabricated via Additive Friction Stir Deposition

Improving grain structure and dispersoid distribution of nanodiamond reinforced AA6061 matrix composite coatings via high-speed additive friction stir deposition

Improving grain structure and dispersoid distribution of nanodiamond reinforced AA6061 matrix composite coatings via high-speed additive friction stir deposition

Additive friction stir processing and hybrid metal additive manufacturing of high melting point materials: A review

Ever since the beginning of 4th industrial revolution, metal additive manufacturing has revolutionized the paradigm of printing high melting point materials. In this context, this paper reviews experimental and computational aspects of friction stir processing and hybrid techniques applied for metal additive manufacturing of high melting point materials like steel, and titanium alloys. Initially, friction stir processing working principle has been discussed. Secondly, friction stir processing is compared with other severe plastic deformation techniques and summarized their advantages, disadvantages and applications in a tabular form. Then based on the state-of-the-art of literature, additive friction stir processing and hybrid metal additive manufacturing processes are discussed for high melting point materials and results have been presented with respect to their microstructural developments, mechanical behavior, etc. Finally, gaps are highlighted for high melting point materials that shows importance of selecting process parameters, tooling capacity, computational analysis, mathematical modelling, etc., and presented these as future scope of work.

Hybrid manufacturing by additive friction stir deposition, metrology, CNC machining, and microstructure analysis

Aerospace flight panels must provide high strength with low mass. For aluminum panels, it is common practice to begin with a wrought plate and remove the majority of the material to attain the desired structure, comprising a thinner plate with the desired pattern of reinforcement ribs. As an alternative, this study implements hybrid manufacturing, where aluminum is first deposited on a baseplate only at the rib locations using additive friction stir deposition (AFSD). Structured light scanning is then used to measure the printed geometry. This geometry is finally used as the stock model for computer numerical control (CNC) machining. This paper details the hybrid manufacturing process that consists of: AFSD to print the preform, structured light scanning to generate the stock model and tool path, three-axis CNC machining, and post-process measurements for part geometry and microstructure.

Process planning for hybrid manufacturing using additive friction stir deposition

Additive friction stir deposition (AFSD) provides a solid-state approach to metal deposition that does not rely on local melting and solidification, but rather on kinetic energy and plastic flow. In this study, AFSD is combined with structured light scanning, turning, and milling to produce metal components while considering the unique requirements imposed by the hybrid manufacturing process sequences. Two demonstrations are presented which include: 1) a cylindrical build plate selection to enable coordinate system transfer between deposition and turning of a hollow cone; and 2) intermittent deposition-machining operations with structured light scanning to fabricate a two-sided hexagon-cylinder geometry.

Additively Manufactured Parts from AA2011-T6 Large-Diameter Feedstocks Using Friction Stir Deposition.

The current work investigates the possibility of fabricating additive manufacturing products in solid-state form, from AA2011-T6 of 40 mm diameter rods as a feedstock, using an additive friction stir deposition (A-FSD) technique. The use of large diameter feedstocks, especially high-strength aluminum alloys (2XXX series), is a challenge, as it necessitates high power and the critical selection of the optimal A-FSD parameters, such as feed rate and spindle rotation speed. The study included applying a wide range of spindle rotation speeds, ranging from 400 to 1200 rpm, at three levels of feeding rates of 1, 3, and 5 mm/min. The AA2011-T6 friction stir deposited parts (FSDPs) were visually evaluated. This was followed by an examination of macrostructures through the thickness of the fabricated specimens. The characterization of microstructures was also carried out using optical microscopy and a scanning electron microscope equipped with advanced EDS analysis. Furthermore, the mechanical properties in terms of hardness and compressive strength of the AA2011-T6 base material (BM) and deposited materials were evaluated. Sound, additively manufactured products were successfully fabricated from 40 mm diameter AA2011-T6 feedstocks using the suggested deposition variables of 600 and 800 rpm spindle speeds and feeding rates of 1, 3, and 5 mm/min. The results indicated that the spindle speed and feeding rate govern the quality of the FSDPs. Furthermore, the axial load during the A-FSD process increased with increasing these parameters. In comparison to the AA2011-T6 BM, the additively deposited materials showed a refined grain structure and uniform dispersion of the fragment precipitates in their continuous multi-layers. The reduction ratio in grain size attains 71.56%, 76%, and 81.31% for the FSDPs processed at 800 rpm spindle speed and feeding rates of 1, 3 and 5 mm/min, respectively, compared to the grain size of BM. The Al2Cu and Al7Cu2Fe intermetallics are detected in the AA2011-T6 BM, and their deposited parts are in different shapes of spherical, almost spherical, irregular, and rod-like shapes. The compressive strength and hardness of the deposited parts increased with increasing spindle speed and feeding speeds. At a spindle speed of 800 rpm and a 5 mm/min feeding rate, the higher hardness and compressive strength gained were 85% and 93%, respectively, from that of the AA2011-T6 feedstock.

Quantitative study on the correlation between microstructure and mechanical properties of additive friction stir deposited 6061-T6 Al-Mg-Si alloy

Additive friction stir deposition (AFSD) technology is attractive for its ability to create freeform and fully dense structures without melting and solidification. Hence, AFSD is an alternative to fusion-based additive manufacturing technology. However, the quantitative relationship between mechanical properties and microstructure has not been established yet. The purpose of the research is to establish a quantitative relationship between the microstructure and mechanical properties of AFSD-ed 6061-T6 aluminum alloy. In this study, 6061-T6 aluminum alloy feedstock was processed using AFSD technology and then subjected to post-deposited heat treatment (PDHT). The microstructure evolution and mechanical properties of the feedstock, as-deposited and PDHT-ed 6061-T6 aluminum alloy specimens, were investigated for a comparative study. The microstructure was analyzed using electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Hardness testing and tensile testing were conducted for the feedstock, as-deposited, and PDHT-ed specimens. The strengthening mechanisms were discussed. It was found that precipitation strengthening was the main strengthening mechanism for feedstock and PDHT-ed specimens, which contributed to 69% and 83% of the total yield strength, respectively. Whereas grain refinement strengthening was the main strengthening mechanism for the as-deposited specimen, which occupied 68% of the total yield strength. Finally, the relationship between microstructure and mechanical properties of additive friction stir-deposited 6061-T6 Al–Mg–Si alloy was quantified.