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Friction stir processing (FSP) has been increasingly adopted for joining and processing materials in automotive, aerospace, and industrial construction. During FSP, a dynamic competition between high-speed shear deformation and deformation-induced heating brings about a complex competition between multiple dynamic microstructural evolution mechanisms making it difficult to predict the microstructural evolution pathway. Hence, improved understanding of microstructural evolution mechanisms during FSP can be beneficial for continued growth in the adoption of FSP for demanding applications of future. Towards this goal, this study uses a model binary Cu – 50 at.% Ni alloy to clarify the effect of single and double pass FSP on the microstructural evolution of a coarse grained and compositionally heterogeneous cast microstructure. High energy synchrotron X-ray diffraction, electron backscatter diffraction, and nanoindentation are used to clarify the microstructural evolution due to FSP. The process of compositional homogenization of as-cast segregations is studied by energy dispersive spectroscopy and atom probe tomography. Our results show that a single fast FSP pass at 30 mm.s−1 produces a 100 μm deep layer of submicrometric and hall-petch hardened CuNi grains. The initial cast compositional heterogeneities in a micrometric scale is rapidly transformed to nano-sized domains, mainly confined at grain boundaries. Double pass FSP increases the penetration depth of the processed layer and leads to a 2.9 times grain growth relative to single pass FSP. Grain fragmentation, discontinuous dynamic recrystallization, grain growth, and twinning mechanisms are discussed. These results highlight the value of FSP for ultrafast grain refinement and compositional homogenization of cast alloys.

The trade-off between strength and ductility has been an enormous difficulty in the field of materials for an extended time due to their inverse correlation. In this work, friction stir processing (FSP) was for the first time performed to high-strength and high-melting-point Ni-Co based superalloy (GH4068), and enhanced strength and ductility were achieved in FSP samples. At room temperature, the FSP sample demonstrated significantly higher yield strength and ultimate tensile strength (1290 and 1670 MPa) than that of the base material (BM, 758 and 904 MPa) and advanced wrought GH4068 alloy (982 and 1291 MPa), concurrent with high tensile ductility (∼24%). Compared with the BM, 70% higher yield strength of the FSP sample results from the remarkable contribution of grain-boundary and nanotwin strengthening, which has been confirmed by the multimechanistic model studied in this work. More importantly, with increasing temperature, an excellent strength-ductility synergy was obtained at 400 °C, i.e., the yield strength of the FSP sample was increased by more than 50% compared with the BM (from 789 to 1219 MPa); more interestingly, the elongation was also significantly increased from 17.9% in the BM to 28.5% in the FSP sample. Meanwhile, the Portevin-Le Chatelier effect was observed in the engineering stress-strain curve. The occurrence of this effect may be attributed to the interaction between solutes and defects like twins and mobile dislocations. Moreover, the grain refinement mechanism of FSP samples was proved to be discontinuous dynamic recrystallization.

Together with the mechanical properties, the degradation rate is an important factor for biodegradable implants. The ZKX50 Mg alloy is a suitable candidate to be used as a biodegradable implant due to its favorable biocompatibility and mechanical properties. Current research investigates the degradation rate and corrosion behavior of the ZKX50 as a function of the microstructure constituents and their morphology. Since grain refinement is the main strengthening mechanism for the ZKX50, the effect of the microstructure refinement on the corrosion rate was studied by applying electron beam processing (EBP) and friction stir processing (FSP) on the ZKX50 cast alloy. To study the effect of the microstructure constituents and their morphology a subsequent solution heat treatment (HT) was applied to the processed samples. The results show that the EBP and FSP lead to a uniform and remarkably refined microstructure of the ZKX50 alloy and homogeneous distribution of the intermetallic phases. The results of electrochemical corrosion tests together with the microstructure characterization show that microgalvanic corrosion is the predominant mechanism that occurs between the Ca2Mg6Zn3 intermetallic phase and α-Mg matrix. According to the results attained through the electrochemical tests, the EBPed-HT ZKX50 alloy shows higher corrosion resistance compared to all other conditions immersed in 0.5 wt% NaCl solution. The dissolution and spheroidizing of Ca2Mg6Zn3 particles during the solution heat treatment provides higher corrosion resistance mainly by decreasing the microgalvanic corrosion. The microstructure of the heat-treated samples does not show a significant grain coarsening which can degrade the enhancement of the mechanical properties achieved by the EBP and FSP.

Although having suitable mechanical properties, the high corrosion and resorption rate of biocompatible Mg alloys make them unsuitable for implant applications. Reducing the corrosion rate of the alloys by altering the metallurgical properties can be potentially beneficial for such applications. Friction stir processing (FSP) is an established process to induce changes in the surface microstructure of metals, and in this study, this process has been explored as a potential method to modify the metallurgical microstructure of the alloy. There is an increase of 13 % of microhardness and there is a 21 % reduction in ultimate stress in exchange of 15 % increase in % elongation in friction stir processed AZ31 magnesium alloy. The results indicate that the induced changes in the metallurgical microstructure by FSP process can augment the resistance to corrosion without significantly deteriorating the mechanical properties as observed from tests conducted in a simulated biological environment. Further experimentation is required to optimize the processing condition and establish the relationship between the evolved metallurgical microstructures and the mechanical and electrochemical properties.

In this article, the boron carbide reinforced Aluminium alloy surface composite material was fabricated through the friction-stir processing method. The Al6061 alloy and B4C particles were used as matrix and reinforced materials respectively. The influences of volume percentage of boron-carbide, traveling feed rate, and rotational speed on tensile strength and wear were investigated using the L9 Taguchi technique. The moderate rotating speed and traveling speed of the tool have been preferred to attain optimum responses. The highest tensile strength of 347 MPa and minimum wear of 55 µm were obtained from 15% of the volume of boron carbide particles, 1400 rpm of rotating speed, and 40 mm/min traveling speed of the tool. The optimum Al6061-B4C surface composites micro-structure has also been studied through scanning electron microscope images.

A Co-based tool was employed to weld TA5 alloy to investigate the effects of tool wear on the microstructure evolution and mechanical properties. Results showed that both dense diffusion and loose cracked layers were detected near the surface of as-worn tool, indicating the occurrences of both diffusional wear and abrasive wear. The stir zone (SZ) was divided into the contaminated zone (CZ) and non-contaminated zone (NCZ) according to whether tool constituents were introduced during welding. Continuous and discontinuous recrystallization occurred simultaneously in NCZ, resulting in refined equiaxed α grains. The microstructure in CZ was determined by both thermo-mechanical effects and the content of β-stable tool elements, which reduced α-β transus temperature. As the proportion of tool elements increased, untransformed equiaxed α grains with boundaries rich in foreign elements, transformed acicular α, and retained β emerged successively. The width of transformed needle-like α was decreased to ~ 100 μm, and basket weave structures were obtained when the transition point was reduced to much lower than welding peak temperature. The CZ was provided with extremely high microhardness due to the presences of retained β and needle-like α phases. The SZ tensile specimen was fractured at 824 MPa, 9.1% higher than the BM. Considering periodic tool wear behavior and resultant unique microstructure, the results in this study provide references for the research on material flow and fabrication of high-strength titanium alloy using friction stir processing.

In the present work, the effects of in-process cooling are investigated on the material flow, temperature distribution, axial force, wear resistance, and microstructural and mechanical properties of friction stir processed (FSPed) Al-Si aluminum alloy. The finite element method (FEM) was developed for modeling the process, based on the eulerian-lagrangian technique, and then verified by the experimental force and temperature histories. Next, the material flow and temperature distribution during the friction stir process (FSP) with in-process cooling under different conditions were considered. After that, the experimental investigations, including the optical microscopy, hardness, and wear tests, were conducted. Finally, the stir zone (SZ) shape obtained by experiments and simulation model were compared for the FSPed samples without cooling and with air cooling. The material flow achievements reveal that using a coolant affects the material flow in the pin-driven zone more significantly than in the shoulder-driven zone, leading the SZ to change from the basin shape into the V shape. The SZ shapes obtained from the experiments and the simulation model show a good agreement between the shapes of the samples FSPed without cooling and with air cooling. Moreover, experimental results showed that using in-process cooling reduces Si particles' size and thus significantly increases the hardness and wear resistance. The Si particles size is reduced from 10 μm in the base metal to 2.6 μm and 2 μm in the air-cooled and water-cooled samples. Consequently, the wear mass loss reduced almost 28% and 40%, and hardness increased almost 35% and 80% for the air-cooled and water-cooled samples compared to the processed samples without coolant.

Despite the high strength-to-weight ratio, the poor tribological behavior and sea water corrosion performance of aluminum alloy limit its engineering applications. In this investigation, an attempt is made to obtain good wear and corrosion resistance by fabricating MoS2 and CeO2 reinforced aluminum 7075 matrix hybrid composites through friction stir processing. The microstructural observation suggests intermetallic free uniformly distributed composites are formed. The specific wear and corrosion rates of the fabricated composites are analyzed. The reason behind variation of the responses is investigated. The processing conditions such as rotational speed, traverse speed, tilt angle and mixing ratio of reinforcement powder are optimized for low specific wear rate and low corrosion rate using Taguchi optimization method. The effects of the processing conditions on individual responses are also investigated. Gray relation approach is also adopted for optimizing the processing conditions while considering equal importance of both the output responses.

In the present research, measurement of residual stress induced during turning and threading operations for the fabrication of two types of pin profiled friction stir processing/welding (FSP/FSW) tools, i.e. cylindrical profiled pin tool and cylindrical threaded profiled pin tool, is being dealt with. Workpiece was chosen to be H13 tool steel with a diameter of 22[Formula: see text]mm and 110[Formula: see text]mm length. Turning and threading was done on CNC machine tools using CNMG 12404-THM uncoated tungsten carbide cutting tool. For residual stress measurement of the workpieces, an XRD-based Pulsetec[Formula: see text]-X360n portable residual stress analyzer setup was used. The experimental results show that the cylindrical pin profile tool had a compressive residual stress of [Formula: see text][Formula: see text]MPa and compressive residual shear stress of [Formula: see text][Formula: see text]MPa, while the cylindrical threaded pin profile tool had a compressive residual stress of [Formula: see text][Formula: see text]MPa (51.8% more) and compressive residual shear stress of [Formula: see text][Formula: see text]MPa (40% less). It has been concluded that due to threading operation on the cylindrical threaded pin profile, the value of residual stress is more in it, and since the stress is compressive in nature, it would have a better positive impact while doing FSP/FSW than that of the cylindrical profiled pin tool.

Friction stir processing (FSP) has been used successfully to yield surface composites that offer good wear resistance and high hardness. In this work, an attempt was made to produce SiC particles incorporated within the surface of an A380 Al alloy using FSP under various processing parameters. The microstructure of processed surface was characterized using optical and SEM. XRD was employed to investigate the phases of A380 Al alloy matrix and confirm with EDX mapping the presence of SiC particles. Microhardness test was performed to recognize the variation of hardness values along the cross-section of processed alloy. Pin on disk wear apparatus was used successfully to study wear properties under dry sliding conditions using different applied loads. The results showed that the XRD and EDX mapping confirmed the incorporation of SiC particles within the surface of A380 Al alloy. Refining of α-Al and silicon modification were recognized within the stir zone. Microhardness was changed significantly across the processed region depending on the FSP parameters used. The presence of SiC particles improved the wear properties of A380 Al alloy especially at 1460 rpm tool rotation speed and 0.3 mm plunge depth. © 2020 Karabuk University. Publishing services by Elsevier B.V. This is an open access article under the CCBY-NC-ND license.

The electrochemical properties of a friction stir processed (FSPed) equiatomic CrMnFeCoNi high-entropy alloy (HEA) was investigated in an aerated 0.5 M Na2SO4 electrolyte solution at room temperature. The microstructural analysis reveals a highly refined stir zone (SZ) with an average grain size that decreases from the top region of the SZ to the bottom region of the SZ (also known as shear-processed zone; SPZ). However, the region below the SPZ, (i.e. below the plunge depth) experienced an increase in average grain size and dislocation densities compared to the other regions. There is no secondary phase observed in the FSPed region, however, the microstructural evolution in the FSPed region affects the electrochemical behavior of the HEA. Cr2O3 passive layer was observed to form on the FSPed HEA, leading to excellent corrosion properties from the polarization corrosion tests. Grain refinement in the SZ enhances the rapid formation of the passive layer, thus, leading to better corrosion properties in the front surface of the FSPed HEA. The localized corrosion behavior of the FSPed HEA was predicted to be caused by the micro-galvanic nature of the HEA, which leads to an increase in polarization at the anodic sites (pits). A numerical model was established using the corrosion parameters from the experiment to simulate the localized corrosion behavior on the surface of the FSPed HEA in a neutral environment. The predicted initial pitting potential and corresponding current density agree well with the experimental results. The model is also capable of tracking the dissolution of the pits over longer periods.

Shape memory based high performance nickel-titanium alloy particles were embedded by friction stir processing in graded concentration on the surface of light weight commercially pure magnesium cast plates. The novel functionally graded material so developed was analyzed for microhardness evolution and vibration damping effect. The nickel-titanium alloy particles were filled in a 2.5 wide × 3 mm deep slot and embedded on the surface by friction stir processing. A shallower slot 2.5 wide × 1.5 mm deep was milled over the previously embedded surface in which nickel-titanium alloy powder was again filled and embedded on the surface by second pass friction stir processing. This sequence of pass created the graded variation in nickel-titanium alloy concentration. The so fabricated functionally graded material was cut out from the plate and it was hot-forged to 2/3 thickness and subsequently quenched. The microstructural examination confirmed homogeneous dispersion of nickel-titanium alloy particles and clear interface between high and low concentration regions. The microhardness confirmed a uniform graded variation in hardness. The vibration damping tests confirm considerable improvement in the damping capacity of the fabricated functionally graded material.

Friction stir processing (FSP) was used to modify the microstructure and improve the mechanical properties and corrosion resistance of an Mg–Al–Ca alloy. The results demonstrated that, after FSP, the grain size of the Mg–Al–Ca alloy was decreased from 13.3 to 6.7 μm. Meanwhile, the Al8Mn5 phase was broken and dispersed, and its amount was increased. The yield strength and ultimate tensile strength of the Mg–Al–Ca alloy were increased by 17.0% and 10.1%, respectively, due to the combination of fine grain, second phase, and orientation strengthening, while the elongation was slightly decreased. The immersion and electrochemical corrosion rates in 3.5 wt% NaCl solution decreased by 18.4% and 37.5%, respectively, which contributed to grain refinement. However, the stress corrosion cracking (SCC) resistance of the modified Mg–Al–Ca alloy decreased significantly, which was mainly due to the filiform corrosion induced by the Al8Mn5 phase. SCC was mainly controlled by anodic dissolution, while the cathodic hydrogen evolution accelerated the SCC process.

The modified layer was prepared by adding carbon fiber (Cf) and TiB2 to 7075 aluminum alloy using friction stir processing (FSP). The metallographic microscope was used to analyze the microstructur...

Multi-walled carbon nanotube/aluminum composites are fabricated on Al–Si cast alloy employing friction stir processing. First, the microstructure of the stir zone, as well as the effect of process parameters on the size of silicon particles, is investigated. Then, the process is numerically simulated using a thermo-mechanically coupled three-dimensional finite element method model. Material flow, as the primary reason for the dispersion of reinforcing particles, is considered in the numerical model, and proper conditions to obtain a uniform dispersion of multi-walled carbon nanotubes are determined. Scanning electron microscope analysis is carried out to consider the particle distribution in the texture of the stir zone. The results show that the particle distribution improves significantly by changing the tool rotation direction between the friction stir processing passes. The hardness test is accomplished on the cross-section of the friction stir processed specimens, and finally, the wear test is performed to compare the wear resistance of the composites with the base alloy. The results show that the wear resistance and hardness of the produced composites are considerably enhanced compared to the base alloy.

The purpose of this study is to observe the change in the microstructure of the magnesium AZ91 alloy with the help of refinement of the grain structure due to Friction Stir Processing (FSP), result...

Aluminum alloys find application in aerospace, automobile, and structural sectors. However, these alloys are susceptible to corrosion attack in chloride environments. Introducing a second species on the surface by surface composite fabrication can be a way to increase the corrosion resistance of the aluminum alloys. Here, we present corrosion studies on aluminum matrix surface composites fabricated using friction stir processing. The reinforcement of Mo particles is considered with varying percentage and distribution in the surface composite. The particle content and distribution are analyzed using SEM–EDS and optical image analysis. Based on the potentiodynamic polarization analysis, the surface composites exhibit improved corrosion resistance with higher corrosion potential and lower corrosion rate. Increase in corrosion resistance is observed for higher Mo content with homogenous distribution. While the base alloy exhibit mixed corrosion behavior, the surface composites show charge-transfer controlled corrosion behavior in the Electrochemical Impedance Spectroscopy. Reduced pitting in the Mo-rich areas is confirmed by microscopic analysis of the corroded material.

The paper presents the results of research on the microstructure and selected mechanical properties of the SnSbCu bearing alloy after friction stir processing (FSP). The Whorl tool was used for modification; the process was carried out using two rotational speeds of the tool: 280 and 450 RPM and a constant linear speed of 355 mm/min. Microstructure studies were performed employing the techniques of light microscopy and scanning electron microscopy along with analysis of the chemical composition of micro-areas. Additionally, the phase composition was investigated by means of the X-ray diffraction method and statistical analysis of the precipitates present in the investigated alloy. In addition, hardness, flexural strength and uniaxial compression tests were performed before and after FSP modification. It was proved that using FSP to modify the SnSbCu alloy promotes refinement and homogenization of the microstructure, as well as improvement of the flexural strength, whereas no changes in the hardness level were found.

In this investigation, the friction stir processing (FSP) method was utilized to improve the properties of the surface of the as-cast nickel aluminum bronze (NAB) alloy in two different processing parameters. The microstructure, element distribution and mechanical properties of the alloys before and after FSP were observed and estimated. The cavitation erosion behaviors of the original NAB and FSP NAB in different test solutions were also discussed. The results indicated that the microstructure became finer and more homogeneous and the element distribution became more uniform after FSP. The FSP NAB alloys also possessed better mechanical properties. The lower cumulative cavitation erosion mass loss of FSP NAB in all test solutions indicated the fact that the cavitation erosion resistance of the as-cast NAB could also be improved by the FSP method. Compared to the as-cast NAB, the corrosion effect on the cavitation erosion was more significant for the FSP NAB alloys owing to their better pure cavitation erosion resistance.

A laminated composite of Al-Zn alloy reinforced with copper powder has been fabricated using friction stir additive manufacturing (FSAM). For this purpose, friction stir processing (FSP) was performed in one to four passes on Alclad Al-Zn aluminum alloy sheet. The results showed that, depending on the rotational and traverse speeds, a protective high-purity aluminum layer on the surface of Alclad Al-Zn emerged from the interface and formed an integrated protective layer in the areas around and away from the stir zone. An Al-Cu intermetallic (Al2Cu) layer formed at the interface of the large reinforcement particles. However, in smaller particles, the copper particle reacted completely with Al. Composite fabrication using a rotational speed of 800 rpm, traverse speed of 40 mm/min, and two passes resulted in a 26.3% increase in the maximum ultimate tensile strength (UTS) to 422.69 ± 4.31 MPa and a 2.6% increase in elongation in 25.31 ± 2.11% compared with a powderless double-layer sample.

The goal of the present research is to introduce the Tungsten (W) nanoparticles as reinforcement into Al 6063 alloy to produce Al–W nanocomposites by the FSP technique. The vol% of the reinforcement was varied from 3 to 12 with a step of 3, besides the unreinforced Al matrix was considered as 0 vol% for comparison. The role of W nanoparticles in the Al 6063 matrix has been exhaustively investigated using advanced characterization techniques such as XRD analysis to observe the phases, FESEM to detect the distribution of reinforcements with their interparticle spacing and the average grain sizes, TEM analysis to study the strengthening factors, new phase formation at the interface between AA 6063 matrix and W particles, the morphology of the W nanoparticles. The achieved average matrix grains size was 42, 2, and 0.9 μm for 0, 6, and 12 vol% W nanocomposites, respectively. The obtained results disclosed the uniform dispersion of W nanoparticles, without any agglomeration, and with the absence of intermetallic compounds. The hardness and wear resistance of the fabricated nanocomposites were increased incommensurate with the incorporation of heavy metallic W element as reinforcement particle; which was due to the proper dispersion of W nanoparticles, refinement of matrix grains to ultrafine level, generation of dislocations, and clear interface between Al 6063 matrix and W nanoparticles. In a nutshell, AA 6063–12 vol% W nanocomposite has achieved the higher hardness (120 HV), lower wear rate (0.13 mm3/m), and friction coefficient (0.33) than other nanocomposites The goal of the present research is to introduce the Tungsten (W) nanoparticles as reinforcement into Al 6063 alloy to produce Al–W nanocomposites by the FSP technique. The vol% of the reinforcement was varied from 3 to 12 with a step of 3, besides the unreinforced Al matrix was considered as 0 vol% for comparison. The role of W nanoparticles in the Al 6063 matrix has been exhaustively investigated using advanced characterization techniques such as XRD analysis to observe the phases, FESEM to detect the distribution of reinforcements with their interparticle spacing and the average grain sizes, TEM analysis to study the strengthening factors, new phase formation at the interface between AA 6063 matrix and W particles, the morphology of the W nanoparticles. The achieved average matrix grains size was 42, 2, and 0.9 μm for 0, 6, and 12 vol% W nanocomposites, respectively. The obtained results disclosed the uniform dispersion of W nanoparticles, without any agglomeration, and with the absence of intermetallic compounds. The hardness and wear resistance of the fabricated nanocomposites were increased incommensurate with the incorporation of heavy metallic W element as reinforcement particle; which was due to the proper dispersion of W nanoparticles, refinement of matrix grains to ultrafine level, generation of dislocations, and clear interface between Al 6063 matrix and W nanoparticles. In a nutshell, AA 6063–12 vol% W nanocomposite has achieved the higher hardness (120 HV), lower wear rate (0.13 mm3/m), and friction coefficient (0.33) than other nanocomposites.The goal of the present research is to introduce the Tungsten (W) nanoparticles as reinforcement into Al 6063 alloy to produce Al–W nanocomposites by the FSP technique. The vol% of the reinforcement was varied from 3 to 12 with a step of 3, besides the unreinforced Al matrix was considered as 0 vol% for comparison. The role of W nanoparticles in the Al 6063 matrix has been exhaustively investigated using advanced characterization techniques such as XRD analysis to observe the phases, FESEM to detect the distribution of reinforcements with their interparticle spacing and the average grain sizes, TEM analysis to study the strengthening factors, new phase formation at the interface between AA 6063 matrix and W particles, the morphology of the W nanoparticles. The achieved average matrix grains size was 42, 2, and 0.9 μm for 0, 6, and 12 vol% W nanocomposites, respectively. The obtained results disclosed the uniform dispersion of W nanoparticles, without any agglomeration, and with the absence of intermetallic compounds. The hardness and wear resistance of the fabricated nanocomposites were increased incommensurate with the incorporation of heavy metallic W element as reinforcement particle; which was due to the proper dispersion of W nanoparticles, refinement of matrix grains to ultrafine level, generation of dislocations, and clear interface between Al 6063 matrix and W nanoparticles. In a nutshell, AA 6063–12 vol% W nanocomposite has achieved the higher hardness (120 HV), lower wear rate (0.13 mm3/m), and friction coefficient (0.33) than other nanocomposites.

In this work, friction stir processing (FSP) was applied to the high-strength and high-melting-point Ni–Fe-based superalloy (HT700) for the first time with negligible wear of the stir tool. Different rotation rates were chosen to investigate the effect of heat input on microstructure and tensile properties at different temperatures of friction stir processed Ni–Fe-based superalloy. The results showed that with increasing rotation rate, the percentage of high-angle grain boundaries and twin boundaries gradually decreased whereas the grain size initially increased and then remained almost constant; the difference in tensile properties of FSP samples with rotation rates of 500–700 rpm was small attributing to their similar grain size, but the maximum strength was achieved in the FSP sample with a rotation rate of 400 rpm and traverse speed of 50 mm/min due to its finest grain size. More importantly, we found that the yield strength of all FSP samples tensioned at 700 °C was enhanced clearly resulting from the reprecipitation of γ′ phase. In addition, the grain refinement mechanism of HT700 alloy during FSP was proved to be continuous dynamic recrystallization and the specific refinement process was given.

Tungsten inert gas (TIG) welding is the most commonly used joining process for aluminum alloy for AA6061 and AA7075 which are highly demanded in the aerospace engineering and the automobile sector, but there are some defects occur during TIG welding like micro-crack, coarse grain structure, and porosity. To improve these defects, the TIG welded joint is processed using friction stir processing (FSP). This paper presents the effect of friction stir processing on TIG welding with filler ER4043 and ER 5356 for dissimilar aluminum alloy AA6061 and AA7075. The mechanical characterization, finite element formulation and mathematical equations of heat transfer of TIG + FSP welded joints are investigated using ANSYS Fluent software by adjusting process parameters of FSP. The results show that the maximum compressive residual stress 73 MPa was obtained at the fusion zone (FZ) of the TIG weldment with filler ER4043, whereas minimum compressive residual stress 37 MPa was obtained at stir zone (SZ) of the TIG + FSP with filler 5356. The maximum heat flux 5.33 × 106 W/m2 and temperature 515 °C have observed at tool rotation 1600 rpm with a feed rate of 63 mm/min. These results give a satisfactory measure of confidence in the fidelity of the simulation

In this work the feasibility test of friction stir processing (FSP) of 1.5 mm thick austenitic stainless steel cold spray coating deposited on 304L stainless steel substrate was performed using tungsten carbide tool. Applied FSP parameters (advance speed 50 mm/min, rotation speed 300 rpm, axial force 20 kN, tilt angle 1.5°) allowed to perform FSP treatment with a higher depth than the coating thickness. As a result, the material mixing at the coating/substrate interface was observed. The microstructure observation revealed that the coating microstructure in the stir zone was significantly modified. EBSD analysis confirmed that full material recrystallization during FSP allowed to formation of dense and uniform fine-grain structure with the mean grain size 1.9 mm. Average coating microhardness was decreased from 406 HV to 299 HV. Further FSP parameters optimization should be carried out in order to improve the process reliability and avoid any coating failure during treatment.

Stir casting is employed for successful casting of aluminum-based metal matrix composite (MMC) plates of 12 mm thickness. Surface imperfections, porosity and reinforcement agglomeration are the main concerns in stir casting processes. Solid state friction stir processing (FSP) enhances mechanical characteristics by grain refinement and uniform distribution of reinforcement of MMC. Some of the crucial specifications of FSP include the tool traverse speed, tool rotational speed, tool shoulder diameter (D/d) ratio, pin design, pin length and axial force. In this investigation, five varying tool traverse speeds ranging between 20 mm and 60 mm per min were experimented on the stir cast plates. The wear rate, microstructure and microhardness evaluation on FSP plates revealed that wear resistance of 40 mm/min tool traverse speed FSP plate is superior and attribute to significant microhardness values. In addition, fine grains, uniform distribution and SiC particle bonding with aluminum matrix contribute to effective resistance to wear.

Magnesium (Mg) and its alloys are currently under consideration for use as temporary implants. However, early degradation and maintaining mechanical integrity is a significant concern. Surface modification techniques are used to improve mechanical and corrosion properties of Mg based alloys. In the present study, friction stir processing (FSP) was used to tailor the surface characteristics of Mg-1Zn-2Dy (wt.) alloy for temporary implant applications. The FSPed alloy was characterized using EBSD to understand the influence of FSP on crystallographic texture, grain size and grain boundaries and thereby their effect on corrosion, wettability and hardness. Results showed that the grain size of stir zone (SZ) was refined to less than 3 I¼m, as a result of dynamic recrystallization (DRX) during FSP and the FSPed alloy exhibited better wettability than as-cast alloy. An increase in the hardness (11.7) and elastic modulus (6.84) of FSPed alloy were also observed. Electrochemical corrosion and weight loss methods were conducted in Dulbecco's Modified Eagle's Medium (DMEM) with, 10 Fetal Bovine Serum (FBS) physiological solution. The lower degradation rate (0.72 mm/yr) of FSPed alloy has been attributed to the fine grains and evenly distributed secondary phase particles. Further, the influence of grain boundary characteristics and crystallographic texture on the corrosion behavior have been investigated. © 2021 The Author(s).

The effect of multi-pass friction stir processing (FSP) on the tribological properties of conventionally-cast Al-8.5Fe-1.3V-1.7Si (FVS0812) alloy was investigated. The pin-on-disk dry sliding wear tests were conducted at room temperature under the applied pressures of 0.25, 0.50, and 0.75 MPa. The results showed that FSP substantially refined and improved the distribution of coarse θ-Al13Fe4 platelets and α-Al12(Fe,V)3Si intermetallics in the microstructure of alloys and eliminated the intermetallic-related defects. Consequently, the mechanical properties of the alloys, especially their ductility, were improved, which enhanced the stability of the protective tribolayer formed on their worn surfaces. According to the wear test results, the FSPed samples showed improved tribological properties especially at the higher applied pressures. For instance, at the applied pressure of 0.75 MPa, the wear rate and average friction coefficient of four-pass FSPed sample were lower than those of the base as-cast sample by 97% and 52%, respectively. SEM examination of the worn surfaces and wear debris also demonstrated that the wear mechanism changed from severe delamination/abrasion and microcracking of the tribolayer in the as-cast samples to mild delamination/abrasion and minor plastic wear in the FSPed samples.

The present work studies the effect of microstructure and precipitate formation on mechanical and corrosion characteristics of friction stir processed AA6061 alloy using different cooling technologies (cryogenic and water cooling). The results revealed that recrystallized fine grains formed in all friction stir processing samples (grain size within a range of 2–6 µm) as a result of dynamic recovery and recrystallization, while samples processed in cooling-assisted friction stir processing resulted in better grain refinement in the stir zone than in air-cooled friction stir processing. Three kinds of precipitates (Fe-based needle-shaped precipitates, Si-based round-shaped precipitates, and chain of small round-shaped Si-based precipitates) were identified in base material and friction stir processing samples. Compared to air-cooled friction stir processing, in cooling-assisted friction stir processing, the hardness and tensile strength increased but remained lower than for the base alloy due to the presence of high density Fe-based needle-shaped precipitates. The ductility after friction stir processing greatly improved due to thermal softening and dissolution of precipitates. The corrosion results demonstrated that the corrosion resistance greatly enhanced after friction stir processing due to uniform distribution of grain structure and discontinuous chain of small round-shaped Si-based precipitates in stir zone. Moreover, cooling-assisted friction stir processing resulted in improved corrosion resistance compared to air-cooled friction stir processing due to the formation of fine precipitates.

Post-heat treatment was conducted on the Al-Zn-Mg-Cu-Sc-Zr alloy treated by friction stir processing (FSP) to optimize its strength and corrosion resistance. Different post-heat routes had significant bearing on the phase composition of the FSP sample, while its fine equiaxed grain structure could be retained during post heating. Enhanced strength of the FSP sample was obtained by post-heat treatments. The FSP sample after T6 treatment (artificial aging to peak hardness value after solid solution treatment) exhibited the highest strength in virtue of its high precipitation strengthening effect, and the high ductility of the FSP sample could be retained after solid solution treatment. Furthermore, the FSP sample presented better corrosion resistance after artificial aging and T6 treatment by reducing its solution atom numbers.

In the fabrication of light weight structural materials, the as-cast ZK60 magnesium alloy plays a vital role in the replacement of aluminum alloy. As the wear and friction properties are poor for magnesium alloys, it is very much essential to adopt surface engineering to enhance these properties. Friction stir processing is one of the promising thermo-mechanical processing techniques that alters the grain refinement and surface properties of the material. This investigation is made to understand the impacts of tool traverse speed ranges from 5 to 25 mm/min in cast ZK60 and FSPed/ZK60/SiCp magnesium alloy friction stir processed zone formation. It is found that the FSP made by using the high tool traverse speed of 10 mm/min exhibited higher hardness (121.2HV) and uniform particle distribution in the processed zone. This may be attributed to the dispersion and grain boundary strengthening. Also, this study is further proceeded to transient temperature distribution during FSPed/ZK60 Mg alloy by using Finite Element method. From simulation, the maximum temperature determined is 462°C, which is notably less compared to the melting temperature of the plate.

In this work, we successfully prepared a NAB/Zn composite using Zn wires by friction stir processing (FSP). During FSP, Zn-containing α matrix and (Fe, Ni)Al phases and nano α and CuZn grains with the size of less than 10 nm are formed on the top surface. The average microhardness of the composite is increased by 15 pct compared with the alloy without Zn, which originates from fine grains, CuZn particles strengthening, and more β′ phase.

The surface structure and properties of a cast piston alloy were improved after friction stir processing at a tool rotation rate of 710 rpm and tool traverse speed of 100 mm/min. The microstructure...

The aim of this study was to form a low-carbon steel/TiN surface composite using duplex friction stir process (FSP) and plasma nitriding (PN). First, titanium powder was added to the steel surface by FSP through the pre-determined holes. After applying FSP, the specimens were subjected to plasma nitriding. The specimens were examined by optical and scanning electron microscopes, x-ray diffraction (XRD) analysis, microhardness test and pin-on-disk wear tests. Results of optical and scanning electron microscopy showed that the FSP process was successfully applied on the surface and modified the surface microstructure of the low-carbon steel. The surface hardness of the FSP sample increased by 42% over the hardness of the low-carbon steel and exhibited better wear resistance than the base metal. On the other hand, plasma nitriding also increased the surface hardness of the sample and the measured hardness was about 823 Vickers. This measured value was far greater than the 185 and 130 Vickers obtained for FSP steel and low-carbon steel, respectively. Due to the formation of TiN and the compound layer on the surface of the plasma nitriding sample, the highest wear resistance was obtained as compared with the other samples. For this sample, the wear mechanism was a combination of oxidation and adhesive.

Friction stir processing is demonstrated to effectively enhance the surface and bulk properties of aluminum composites fabricated via the stir casting route. This process is performed below the melting point of the base material wherein common conventional fabrication problems such as solidification, liquidation cracking, and porosity are eliminated to a significant extent. Five different tools with varying tool diameter ratios are experimented on while maintaining tool rotational and traverse speeds and axial force constant. In this investigation, the hardness and wear characteristics of the LM25 aluminum alloy reinforced with 5% silicon carbide particles composite is studied. It is concluded that the tool with a tool diameter ratio of 3.0 resulted in a defect-free processing zone, refined grains, and a minimum particle size enhancing the wear resistance and hardness as compared to that for other values of a tool diameter ratio.

In this study, the wear behavior of AA7075-T6 has been significantly improved by encapsulating TiC and graphite nanoparticles using FSP. The wear tracks and debris SEM EDX analysis confirms that the prominent wear mechanism changed from fretting fatigue to abrasion due to the presence of TiC/Gr mechanically mixed layer at contacting surfaces. The tool rotational speed-w rpm (39%), TiC/Gr vol% (14%), the interaction effect of tool rotational speed and TiC/Gr hybrid ratio HR (17%) and interaction effect of tool traverse speed v-mm/min and vol% (23%) observed to be most influential factors. The lowest wear rate was observed for the Run 19 surface composite produced at lower rotational, traverse speeds and with higher volume percentage TiC/Gr with the weight ratio of 60:40. The ranges of parameters that hold suitable for retaining the inherent precipitates along with the dispersion of graphitized-TiC particles have been traced successfully, and the prediction equation of wear rate is defined. Subsequently, it has been validated through observed confirmation results. The predicted and experimental values showed a good association. The inherent isomorphous precipitates dissolution due to excessive intense plasticization has been confirmed through FESEM analysis. The interfacial bonding of TiC/graphite nanoparticles with the base alloy matrix was found to be the necessary condition in controlling the wear rate. The composites processed at lower tool stirring parameters have resulted in good wear properties since it retained inherent precipitates along with the dispersion of graphitized-TiC particles. The wear rate was found to be a function of graphite content inside composites.

Multipass friction stir processing (MP-FSP) is a solid-state surface modification technique, which was developed based on the simple principle of FSW. Aluminium plates were subjected to MP-FSP from 1 to 14 passes along the longitudinal direction with the specified process parameters such as rotational speed of 1000 rpm and travel speed of 70 mm/min and axial force of 15 kN. Subsequently, similar process parameters had followed by doublepass friction stir processing (DP-FSP) in order to help determine the effectiveness of multipass in creating high strength of aluminium alloys. Now-a-days extensive research had focused on various process parameters such as rotational speed, traverse speed, tool design on processing of aluminium alloys and proficiently enhanced material properties. This technique has considered mostly development of green technology, which is energy efficient and environment friendly technique. Experimentally proven that the Al-Zn-Mg-Sc alloys are characterized through OM, FESEM, DSC, SEM, TEM, and mechanical properties. The tensile strength and ductility of the MP-FSP specimen improved significantly to 122.48%, and 42.55% respectively, but hardness decline to 4.84% as compared to DP-FSP. This is due to not only for refinement of cast dendritic structure and eliminate segregation in the as-cast alloy, but also to the refining of grains, such as the uniform distribution of Al3Sc and hardening precipitates. To aim of this research work is to mainly focusing on MP-FSP may enhance mechanical properties better than DP-FSP and useful for macroscale applications.

The present-study accustomed aluminum 2014-T6 alloy of 3 mm sheet as the work material for conducting the friction stir processing. The entire studies have been completed in two phases of work. In ...

Crack repairing of aluminum alloys is done using conventional welding techniques or mechanical methods, which results in the redundancy of mechanical properties due to defects formation. Friction Stir Welding/Processing (FSW/FSP) is a solid-state joining technique which is used to join various different similar and dissimilar metals, along with the fabrication of surface composites to cater the mentioned problem. The objective of this study is to repair the crack produced in 6061 aluminum alloy by the reinforcement of ceramic particles, Al2O3 and B4C, to further increase the efficiency of the joint along the crack line. Weld parameters, equipment used and the processing conditions are emphasized. The mechanical testing and the characterization of the weld as well as base metal was done and compared using tensile testing, micro hardness test and microstructural analysis. X-Ray Diffraction (XRD) was performed for crystallinity and intermetallic study. The dispersion of the particles was investigated using Field Emission Scanning Electron Microscope (FESEM). The crack in the Al-6061 was effectively repaired using FSP. The reinforced samples showed improved mechanical properties as compared to non-reinforced ones.

In the present paper, a 3D thermo-mechanical finite element model (FEM) was developed to simulate friction stir processing (FSP) of super duplex stainless steel (SDSS SAF 2507). It aims to study the developed bead residual stresses and thermal history of the processed material. The model was built and solved in the Abaqus environment by considering the temperature dependency of the mechanical and physical properties of the investigated material. The Gaussian moving heat source was adopted to simulate the heat generated by the tool-workpiece interaction and was applied with the help of a developed user subroutine. Similarly, the tool forging force was incorporated as a moving surface load. For validation purposes, FSP was experimentally performed at a fixed rotational speed of 400 rpm, traverse speed of 100 mm/min, and tilt angle of 2°. During the process, the tool-workpiece temperature was measured using an infrared camera. After processing, the developed residual stresses within the processed zone were measured using the drill hole technique. The numerical results were found to agree with measured temperatures and residual stresses. FEM was then used to estimate the temperature history, the residual stress distribution, and the deformation contours in the processed SDSS SAF 2507. The numerically estimated results revealed a broadening in the plasticized zone within the plunging area. Moreover, developed stresses were found to stabilize within 40 mm from the starting point, i.e., two shoulder advancements. According to the estimated temperature history, the sigma phase was predicted not to form.