Friction Stir Processing Parameters Research Articles

Sn/Graphite/Cu reinforced aluminum: An experimental study on fabrication of hybrid surface composite as journal bearing material by friction stir processing

Friction stir processing (FSP) is an energy-efficient and environmentally friendly technique that provides tailored manufacturing possibilities for surface composites in solid-state conditions. This study focuses on manufacturing solid lubricant-reinforced aluminum matrix surface composite (AMSC) through FSP, which can be used as a journal-bearing material. Composite fabrications are performed utilizing Sn, Cu, and graphite particles (hybrid powder) with four passes of FSP. The cross-sectional macro and microstructures of obtained surface composites are investigated via optical microscopy (OM) and scanning electron microscopy (SEM). The stir zone (SZ) chemistry is analyzed with energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The microhardness measurements show the effects of hybrid powder as reinforcement and FSP parameters on the mechanical features of the composite cross-sections. Wettability and tribological tests are also conducted to determine the surface properties of the fabricated composites. According to the findings, the wear rate is decreased by 8 % with the reduction of average CoF to 0.75, while a hardness increment is achieved over ∼35 % in manufactured surface composites compared to the base material. It is observed that the content and amount of the hybrid powder and FSP parameters employed can ensure the fabrication of desired characteristics compatible with the aim in surface composites.

Optimizing friction stir processing parameters for aluminium alloy 2024 reinforced with SiC particles: A taguchi approach of investigation

The present investigation focuses on the microstructural behavior and mechanical properties of Aluminium alloy 2024 reinforced with SiC nanoparticles by applying the Friction Stir Processing (FSP) technique. Taguchi L9 orthogonal array was used to find the optimal process parameters. The experiment used the expected best process parameters, which confirmed the predicted highest value for the mechanical characteristic. Traverse speed, axial load, and rotating speed are the main factors affecting aluminum metal matrix composite. Hence, this experiment examined the effects of five different tool spinning speeds, specifically 800, 900, 1000, 1100, and 1200 rpm. Weld samples are fabricated wherein the stir zone contains SiC nanoparticles. The results of the study indicate that the optimal welding rotational speed of 1000 rpm has a significant impact on the microstructure, wear rate, and microhardness. Specifically, it was observed that the stirred zone exhibited enhanced wear resistance compared to other zones. The study's findings revealed that after implementing friction stir processing (FSP), a well-defined shear zone was observed on the advancing side of the stir zone. Additionally, it is found that the uniform dispersion and strong bonding of SiC particles with an aluminium matrix further enhance wear resistance.

Fabrication of tungsten inert gas-welded dissimilar aluminium joints using different friction stir processing tools through response surface method

ABSTRACT AA6061-T6 and AA7075-T6 materials find wide application in manufacturing industries due to their excellent engineering properties. Fusion welding generates solidification cracks, high residual stresses, and brittle intermetallic compounds that degrade joint qualities. To solve these difficulties, friction stir processing (FSP) is frequently employed, which improves joint properties through local microstructural refinement. In this study, the combined effect of FSP parameters, namely tool pin profile (TPF), tool rotation speed (TRS), and travel speed (TS), on tungsten inert gas (TIG) weld properties was investigated. Response surface methodology (RSM)-based mathematical models were developed to predict responses, namely ultimate tensile strength (UTS), impact toughness (IT), microhardness (MH), and residual stress (RS). The optimal FSP parameters were determined through the desirability function technique. Post-FSP increased the UTS, IT, and MH of TIG welds by 71.51%, 95.40%, and 72.46%, respectively, and decreased the RS by 58.46%. ANOVA findings exhibited that TPF was the most influential parameter, followed by TRS and TS. The dissimilar aluminium TIG+FSP joints showed an optimal UTS of 282.08 MPa, an IT of 17.32 J, a MH of 121.48 HV, and an RS of 22.09 MPa when using a TRS of 1108.49 rpm and a TS of 37.74 mm/min with a THF pin.

Synthesis and characterization of magnesium-titanium carbide nanocomposites via friction stir processing: An in-depth parameter investigation

Magnesium Metal Matrix Composites (MMMCs) possess remarkable mechanical and metallurgical properties that have garnered the interest of researchers worldwide. The current research endeavors to synthesize nanocomposites based on magnesium (Mg), specifically AZ31B, by employing Friction Stir Processing (FSP) and integrating nano-titanium carbide (TiC) as a reinforcing element. Additionally, the impact of various FSP parameters, encompassing transverse speeds (35 and 70 mm/min) and tool rotation speeds (850 and 1700 rpm), on the metallurgical, wear, and mechanical properties of the developed MMMCs was investigated. The microstructural analysis revealed that employing the FSP technique led to a uniform dispersion of nano-TiC reinforcement particles within the base matrix of the AZ31B Mg alloy. This concurrent distribution played a crucial role in both refining and evolving the grain sizes, subsequently leading to improvements in the composites’s mechanical and wear characteristics. To be more specific, the grain size witnessed a reduction by nearly 18 times, the microhardness increased by approximately 2.54 times, and the ultimate tensile strength (UTS) showed a 2.08-fold increase when compared to the base alloy. Furthermore, in contrast to the base material characterized by an adhesive wear mechanism, the presence of scratches indicates that the abrasive wear mechanism predominated in the case of the AZ31B/TiC nanocomposite. The outcome of the results depicts that the nanocomposite fabricated at a tool rotation speed of 1700 rpm and 70 mm/min transverse shows better mechanical and tribological characteristics than other developed composites and the base alloy.

Influence of Processing Parameters on Microstructure and Surface Hardness of Hypereutectic Al-Si-Fe-Mg Alloy via Friction Stir Processing

In this study, the effects of friction stir processing (FSP) parameters on the microstructure and hardness of cast Al-Si-Fe-Mg alloy were investigated. Orthogonal arrays were applied in the design of the experiments. The selected parameters for the experiments included rotation speed, transverse speed, penetration depth, and tilt angle. The microstructure and hardness of the FSPed Al-Si-Fe-Mg were studied using optical and scanning electron microscopy, and microhardness testing, respectively. The quadratic model was proposed to fit the experimental data of hardness. Signal-to-noise ratio (S/N) analysis showed the maximum hardness achieved when rotation speed, transverse speed, penetration depth, and tilt angle were chosen as 1600 rpm, 400 mm/min, 0.1 mm, and 1.5°, respectively. Taguchi’s analysis of variance (ANOVA) was used to determine the significant FSP parameters on hardness, which revealed that rotation speed was the most dominant processing parameter, followed by transverse speed, tilt angle, and penetration depth. Moreover, a quadratic polynomial model was developed to predict and optimize the combination of the parameters, enabling superior mechanical properties. Subsequently, the verification of the microstructure was conducted, demonstrating good agreement between the experimental observation of the microstructure and estimated outcomes.

Enhanced strength ductility and wear resistance in a friction stir processing engineered AZ31B/TiC magnesium-based nanocomposites

ABSTRACTIn the present investigation, efforts have been made to fabricate a magnesium-based AZ31B nanocomposite by integrating nano-sized titanium carbide (TiC) particles via utilising the friction stir processing (FSP) process. The primary objective of the research was to enhance the metallurgical, mechanical, and tribological properties of the base material while investigating the influence of secondary phase particles and various FSP parameters. The findings were rigorously validated through a comprehensive analysis, which encompassed the use of various testing apparatus, such as optical microscopy, field emission scanning microscopy, microhardness testers, tensile and compressive testing machines, along with fractography analysis for wear morphology and tensile properties. The results indicate that the nanocomposite produced under the conditions of a tool rotation speed of 1600 rpm and a transverse speed of 40 mm/min along with three number of FSP passes exhibits superior mechanical and tribological properties compared to both other developed composites and the base alloy. A significant enhancement of nearly 2.68 times in microhardness values along with simultaneous refinement in grain size up to 14.85 times was obtained. Ultimate tensile and compressive strengths report an impressive increase in values up to 2.16 and 1.6 times respectively when compared to the base metal. Furthermore, the tensile fracture behaviour of the base magnesium alloy indicated brittleness, while the AZ31B/TiC composite displayed a combination of ductile and brittle features. In terms of wear morphology, the base magnesium alloy exhibited adhesive and abrasive wear, while the composite demonstrated particle pull-out, delamination, and localised plastic deformation, with enhanced resistance to wear. These findings underscore the significant improvements achieved in mechanical and tribological properties, thus emphasising the novel contributions of this research to the field.

Corrosion Behaviour of High-Pressure Die-Cast AZ91 Alloy in NaCl Solution: Effects of Friction Stir Process at High Rotational Speed.

The AZ series of Mg alloys have become promising in several industrial fields thanks to its potential microstructure refinement and the β-Mg17Al12 eutectic that controls the mechanical behaviour. Simultaneously, the rapid degradation characterizing Mg alloys makes the investigation of their corrosion behaviour necessary. The present work considers high-pressure die cast (HPDC) AZ91 alloy to evaluate its corrosion behaviour in 1M NaCl solution and investigates how different friction stir process parameters can affect the corrosion responses. No studies analyse the effects induced by the friction stir processed zone, reached using high rotational speeds (>2000 rpm), on the unprocessed HPDC AZ91 alloy. In addition, the morphological analysis of the corroded surfaces having a friction stir processed zone, in which the grain refinement was not obtained, is not present in the literature yet. Microstructural features were investigated by optical microscope and X-ray diffraction analysis before and after the friction stir process. These were subsequently correlated to the corrosion responses after the immersion tests. The results show that HPDC samples with a very smooth surface have the best corrosion resistance with a corrosion rate lower than 3 mm/year, evaluated through the weight loss, compared to the rougher ones. Both the amount of β-Mg17Al12 eutectic and the wt.% Al in the α-Mg matrix, as well as the surface roughness, influence the corrosion behaviour of friction stir processed samples. The best corrosion resistance was obtained with an HPDC alloy processed at 2500 rpm and 50 mm/min.

An overview of friction stir processing of Cu–SiC composites: Microstructural, mechanical, tribological, and electrical properties

Copper matrix composite reinforced with SiC exhibits high electrical and thermal conductivity, as well as superior mechanical properties, making it a potential candidate for thermal management applications. There has been rapid progress in the understanding of Cu–SiC metal matrix composites during the past decade. To accomplish this, powder metallurgy, casting, selective laser melting, composite electroforming technology, and electrodeposition methods have been employed. The optimum cutting conditions for fabrication of Cu–SiC metal matrix composites are still being explored. In recent years, friction stir processing (FSP) has become increasingly popular in the fabrication of composites. FSP is capable of microstructural engineering in Cu–SiC systems. In light of the fact that the electrical/thermal conductivity and mechanical performance of Cu–SiC composites depend on microstructural characteristics such as SiC distribution, grain size, grain orientation, density of dislocations, and bulk density, it seems important to study the effect of manufacturing conditions on microstructure in detail. In this study, the influence of FSP parameters such as rotational and traversal speeds, the number of FSP passes, and the pin profile as well as the characteristics of SiC powder are discussed in detail with regard to macro- and microstructure, hardness, strength, tribological, and electrical properties of FSPed Cu–SiC composites.

Optimization of Friction Stir Processing Parameters for Improvement of Mechanical Properties of AlSi7Mg0.2 Alloy

This paper investigates the effects of Friction Stir Processing (FSP) parameters on the microstructure and mechanical properties of an Al-Si7Mg0.2 alloy. The study’s findings indicate that augmenting the rotational velocity of the tool in the context of Friction Stir Processing can reduce grain size and enhance the alloy’s mechanical properties. The optimization of process temperature plays a vital role in managing the thermal profile and preventing undesirable consequences such as overheating or excessive cooling. These adverse effects can significantly impact the microstructure and properties of the alloy. The finer grain size of the FSPed samples resulted from the intense plastic deformation and dynamic recrystallization during the process. This grain refinement improved hardness, wear, and corrosion resistance. The temperature distribution during FSP using finite element simulation was highly dependent on the process parameters, such as the rotational speed and the dwell time. The results of this study are employed to develop a fitting model to predict the temperature distribution along the workpiece during the dwelling stage, which can be used to optimize the process parameters for different applications. The optimization of the heat generation inside the stirred zone plays a vital role in managing the thermal profile and preventing undesirable consequences such as overheating or excessive cooling. These adverse effects can significantly impact the microstructure and properties of the alloy.

ENHANCING MECHANICAL PROPERTIES AND MICROSTRUCTURE ON MODIFIED SURFACE AL–MG/CR3C2 BY FRICTION STIR PROCESSING

Friction Stir Processing (FSP) is a promising solid state method and it is developed from the Friction Stir Welding (FSW) principle. FSP was employed to enhance the surface characteristics by ceramic particulate reinforced with AA5052 aluminum alloy. Initially, the machined square grove was formed on AA5052 and packed with ceramic particulate. In this research, chromium carbide (Cr3C2) is a ceramic material for improving the surface characteristics of the base material. The FSP parameters such as tool rotational speed, traverse speed and axial forces were utilized in this process. The microstructure evolutions of the processed specimens were observed by optical microscope and Field Emission Scanning Electron Microscope (FESEM) with Electron Dispersion Spectroscopy (EDS). The mechanical properties like processed microhardness and tensile strength of AA5052 friction stir processed specimens were analyzed. The various microstructural zones were observed in the processed regions with dispersion of the particulates Cr3C2. The specimen fabricated at 1000 rpm tool rotational speed, 25 mm/min traverse speed and 7 kN axial force exhibits maximum microhardness and tensile strength with homogeneous dispersion of Cr3C2.

The Role of Friction Stir Processing Parameters and Hybrid ZrC/WC Reinforcement Particles in Improving the Surface Composite Dissimilar Matrix’s Dynamic Behavior and Microstructure Refinement

This study examined the impact of hybrid reinforcement particles, specifically zirconium carbide (ZrC) and tungsten carbide (WC), as well as the parameters of friction stir processing (FSP), on the microstructure, mechanical properties, and dynamic behavior of aluminum alloys. The hybrid particles were integrated into the aluminum alloy using friction stir processing (FSP). The fabricated metal matrix composites (MMCs) were characterized using optical microscopy, scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA). The results showed that the FSP parameters and reinforcement particles played an important role in improving the grain refinement of the MMCs. This study’s results suggest that the FSP samples’ UTS can be maximized using a tool rotation speed of 600 rpm and a traverse speed of 30 mm/min. The grain refinement in the composite surface was attributed to the dynamic recrystallization during the friction stir processing (FSP) process. The reinforcement particles also acted as grain growth restrictors, further refining the grain size. This resulted in a 34% increase in ultimate tensile strength compared to AA2024 alloys and a 12% increase compared to AA7075 alloys. The composite surface also exhibited enhanced dynamic properties, with an increase in impact energy of 26%. The free vibration test showed that the hybrid reinforcement particles significantly improved the strength and damping capacity of the aluminum alloys, resulting in a high resonant frequency. This is important for applications such as vibration damping and noise reduction.

Surface Modification on Magnesium Alloys’ Hardness and Microstructure Using Friction Stir Processing – A Review

Low density of magnesium-based alloy is one potential as the lightest structural material for light weight-high strength applications for automotive and aerospace. Severe plastic deformation (SPD) together with thermomechanical processing are proved to be a successful method for attaining desired microstructural modifications through achieving fine and highly misoriented microstructures and creating various structures to the bulk properties of magnesium alloy. The material's deformation can result in an altered microstructure that is gainful to the material's requirements. However, the poor deformability of magnesium and its alloys limits the application of the thermomechanical approach. Controlling over temperature and deformation rate is hard to achieve. Among the thermomechanical processes, friction stir processing (FSP) offers an easy way to achieve process stability and mechanical properties enhancement by heat treatment which results in the closure of porosity and refined grain size. During this process, heat is generated by the rotation of the FSP processing tool. Few process parameters such as rotational and traverse speeds should be controlled to make FSP stay within the defined processing condition. It is critical to set the right tool rotational speed as well as traverse speed to ensure adequate heat generation. As there are no established standards for operating the FSP, the only solution is to experiment with different settings to find the best parameter which will produce better quality on processed magnesium alloy workpiece. This paper explores earlier studies on surface modification via FSP technique to improve the mechanical properties strengthening of magnesium alloy mainly on grain size and hardness. The surface modification was done mostly on popular series of magnesium alloy (AZ series) using different tool material, tool geometry and different parameters combination. A comprehensive view of surface modification on magnesium alloys which includes the FSP tool and workpiece material used, variations of FSP parameters settings as well as the effect on hardness and microstructure analysis will be discussed.

Evaluation of microstructural, tribological and tensile characteristics of AA7075 surface composites fabricated through friction stir process

Superior wear resistance and a high level of tensile strength in piston ring materials are achieved using AA7075 surface composites (SCs) that are fabricated by reinforcing the steel slag (SS) particulates through proper selection of friction stir process (FSP) parameters using the multipass technique. The optical structure elucidates that fine and equi-axed grains are ascertained in the stir zone of the processed region, and by increasing the number of passes from one to three, a homogenous dispersion of particulates and a reduced grain size (9 µm) is obtained. In particular, a clear and defect-free interface is prominent on the resulting composite surface. Field emission – scanning electron microscopy (FESEM) identifies the dispersion of reinforcements, while X-ray diffraction (XRD) technique and energy dispersive spectroscopy (EDS) mapping confirm the existence of reinforcing elements. The Orowan strengthening effect and reduced oxygen content around the SiO2 and CaO elements in the three-pass FSP SC specimen tend to increase its load-bearing capacity and result in superior hardness (353.3 VHN) and tensile strength (792.6 MPa). However, the same specimen exhibits a reduced percentage (%) elongation due to multiplied fragmentation of reinforcements, which eventually restricts the plastic movement of the AA7075 matrix. The SEM fracture morphology indicates that failure occurred through a combination of ductile and brittle modes. Furthermore, the SC specimen with two passes prominently decreases the wear rate (333 × 104 mm3/m), which can be attributed to the commendable trilayer formation, and the worn morphology indicates the abrasive wear was the dominant wear mechanism. This fabricated specimen with high-strength characteristics can be beneficial for design engineers. During piston ring design, an increased level of the factor of safety can be achieved.

Effects of tricalcium phosphate-titanium nanoparticles on mechanical performance after friction stir processing on titanium alloys for dental applications

Friction Stir Processing (FSP) is a solid-state method that is widely used in titanium and its alloys to enhance their strength. The FSP technique produces low-defect-density materials with improved mechanical properties, making it potentially valuable for orthopedic and dental applications. It is primarily used for low-melting-point materials such as titanium but can also be applied to high-melting-point metals such as steel, nickel, and titanium alloys. When conducting an FSP test, it is crucial to select appropriate tool geometry, rotational speed, tool speed, and workpiece thickness. Scanning electron microscopy (SEM) are commonly used to analyze the phase and morphology of samples containing Tricalcium Phosphate (TCP) and Titanium oxide nanoparticles (Ti-NPs) ceramic. The effect of hydrogenation on the mechanical properties of titanium alloys mixed with titanium during FSP is also investigated. The composition of TCP and Ti-NP is diffused onto the titanium substrate, and it is recommended that Ti-NP be joined to the substrate using FSP. Using FSP, the microstructure can be altered, and the properties of the new design tool can be studied using mechanical testing. The effects of hydrogenation during FSP of two non-homogeneous metals with Ti-NP can be investigated to evaluate the mechanical properties of the joint area and the worn tool mechanism. The pin tool mainly alters the direction of the secondary metal, allowing for an increase in the number and size of this secondary material attached to titanium. FSP parameters can be optimized based on the volume of the joined area using various established techniques.

Experimental investigation on fabrication and characterisation of Mg-Al2O3 surface composites

ABSTRACT The current study attempted to introduce nano-aluminium oxide (Al2O3) particles into ZE41 alloy via friction stir processing (FSP). The effect of these nano-Al2O3 particles on the mechanical and tribological characteristics of ZE41 alloy is investigated. The results of microstructural studies revealed the uniform distribution of Al2O3 particles and substantial grain refinement in the stir zone by FSP. Enhanced microhardness was observed in the processed region due to the grain refinement and the occurrence of regularly distributed Al2O3 particles. The wear resistance was also seen increased with the incorporation of the Al2O3 particles. Moreover, the effect of FSP parameters on the successful incorporation of nano-Al2O3 particles in ZE41 alloy without any defect is also realised.

Artificial neural network prediction and grey relational grade optimisation of friction stir processing

The study predicts friction stir process (FSP) parameters using an artificial neural network (ANN) model. A design of experiment (DoE) approach is used to conduct experiments on FSP and to evaluate the best operating parameters of FSP. ANN uses 30 neurons, 1 hidden layer, and an input and output layer in the Matlab® environment. ANN predicts the output parameters with R values of 0.999, 0.995, and 0.992 for training, validation, and test datasets, respectively, while the overall R-value is 0.997. GRA is used to optimize and rank the parameters of the processes and revealed that the rotational tool speed should be 1180 rpm, traverse feed rate 38 mm/min, and tool tilt angle 1° for best results. The optimized values obtained are 380 MPa, 3.8 µm, 138 HV, and 14% for tensile strength, grain size, microhardness, and elongation, respectively. According to the analysis of variance (ANOVA) and grey relational analysis, the order of influencing parameters on output factors was rotational speed (80%), followed by transverse feed (19%) and tool tilt angle (1%). An ANN is further used to predict using the two most significant parameters—rotational speed and traverse feed. The modified ANN has nearly the same R values as the original ANN. Thus modified ANN may be used for prediction.

The effect of FSP on the friction and wear behaviour of Al5083 under normal atmosphere and vacuum conditions

In current technology, there are a lot of machines that work under vacuum conditions such as in space and aviation. For this reason, friction and wear properties of especially light metals, such as aluminium and magnesium alloys, which are candidates to be used in such areas should be examined under vacuum conditions. In this study, the effect of friction stir processing parameters such as traverse speed and pass number on the microstructure, hardness and wear properties of the Al 5083 alloy were investigated. During the friction stir processing, three traverse speeds and from 1 to 4 passes were applied to the surface of the samples. The wear behaviour of the processed and unprocessed samples was investigated by using the ball-on disc tribometer under air and 5 × 10−3 mbar vacuum conditions. After friction and wear experiments, all FSPed samples showed lesser wear amount under vacuum conditions compared with air conditions.

Optimization of Friction Stir Processing Parameters of Aluminum Alloy Reinforced with Hybrid Nanoparticles Using the Taguchi Method

This study deals with the selection of optimum parameters for friction stir processing of Al alloy 6061-T6 reinforced with a hybrid nanoparticle (B4C and SiO2) in terms of their effect on the mechanical properties (hardness, tensile strength, and wear resistance) using Taguchi method. This work was carried out under four parameters each one running in three levels; rotational speeds (<i>800</i>, <i>1000</i> and <i>1200</i>) rpm, travel speeds (<i>10</i>, <i>20</i>, and <i>30</i>) mm/min, holes depth (<i>2</i>, <i>2.5</i>, and <i>3</i>) <i>mm</i>, and mixing ratio of (SiO2/B4C) nanoparticles (<i>1/1</i>, <i>1/2</i>, and <i>1/3</i>), using <i>L9</i> (<i>34</i>) Taguchi orthogonal array. Tensile strength and microhardness tests were conducted to evaluate the mechanical properties, in addition to the wear resistance test which is carried out using a pin-on-disk device. The microstructure was examined by optical microscopy, field emission scanning electron microscopy, and x-ray diffraction analysis. It was found that the highest tensile strength (<i>223</i>) <i>MPa</i> at <i>1200 rpm</i> rotational speed, <i>30 mm/min</i> traverse speed, <i>2.5 mm</i> holes depth, and <i>1/2</i> (SiO2/B4C) nanoparticles mixing ratio, the highest hardness reached is (<i>155</i>) HV, then decreases in the direction of thermomechanically affected zone (TMAZ), heat affected zone (HAZ), and the base material at (<i>1200</i>) <i>rpm</i> rotational speed, (<i>30</i>) mm/min linear speed, a hole depth of (<i>2</i>) mm and (<i>1/3</i>) mixing ratio of (B4C/SiO2) nanoparticles. The wear behavior was of a mild type or an oxidative type at low loads (<i>5 N</i>), which became severe or metallic wear at higher loads (<i>20 N</i>) at fixed sliding time and speed. The (ANOVA) table has been used to determine which parameter is the most significant using MINITAB software.

Effect of single-pass friction stir processing parameters on the microstructure and properties of 2 mm thick AA2524

Friction stir processing (FSP) is an important method for obtaining fine grains. To determine the effects of FSP and processing parameters on the microstructure and mechanical properties of rolled sheets, we performed single-pass FSP of a 2 mm thick 2524 aluminium alloy (AA2524) rolled sheet by comparing the combination of different processing parameters. The results show that lamellar grains (rolled state) are replaced by fine dynamic recrystallisation in the stir zone (SZ), and more Al2CuMg phases are precipitated simultaneously. As the rotation speed increases, the grain size and width of the pin stir zone (PSZ) increase, the microhardness first decreases and then increases; with the traverse speed increase, the grain size first decreases and then increases, and the width of the PSZ and microhardness decrease. The SZ has the smallest grain size, highest high-angle grain boundaries (HAGBs, with misorientation angles (θ) >15°) ratio, and largest ultimate tensile strength (UTS), when the rotation and traverse speed were 1000 r·min−1 and 125 mm·min−1, are 1.59 ± 0.82 μm, 0.91 and 451.23 ± 0.52 MPa, respectively, and the elongation to fracture is 13%. The UTS and elongation were only 95.12% and 98.48% of those of the base metals (BM), respectively, because of the significant decrease in the dislocation density. Fracture analysis revealed ductile fracture of the joint due to the large number of dimples and fine second-phase particles.

Surface hardening of an Al-Si-Cu-Ni-Mg aluminum alloy by friction stir processing and T6 heat treatment

Friction stir processing (FSP) and standard hardening T6 heat treatment were applied for local surface hardening of the АК12D aluminum (Al-12.8Si-1.67Cu-1.03Ni-0.84Mg-0.33Mn-0.23Co-0.24Fe) alloy plates obtained by hot-compression at elevated temperature. FSP was carried out by introducing a pin into the bulk of the material, followed by its movement along the surface at a traverse speed of 8 and 16 mm / min, accompanied by rotation of the pin at a speed of 2000 rpm. The effect of FSP parameters and T6 treatment on structure and hardness were investigated. It was established that FSP at 2000 rpm and 8 mm / min speed resulted in the formation of a monolithic and defect-free processing zone. The FSP and T6 treatment led to fragmentation of the primary Si and intermetallic phases and partial dissolution of intermetallic phases in the α-Al solid solution followed by decomposition and the formation of dispersed precipitates. The formation of a quasi-equiaxed fine-grained structure was observed after FSP and T6 heat treatment in the stir zone. The measured Brinell hardness demonstrated an average value of 128 HB after treatment versus 103 HB in the initial state. The work reveals the features of the local surface structure refinement allowing to figure out approaches to the design of constructions with enhanced properties.