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Purpose: This research aims to examine the impact of friction stir processing (FSP) treatment on an aluminum alloy, especially the AD31T alloy derived from the Al-Fe-Mg-Si system. The aim is to assess the influence of different processing techniques on the microstructure and physical and mechanical characteristics of the material, with a specific focus on structural and bulk imperfections inside the stir zone (SZ). Design/methodology/approach: The study demonstrates that augmenting the linear velocity of the tool within the 25–100 mm/min range results in significant enhancements. The enhancements include a decrease in the heat-affected zone (HAZ), a reduction in the extent of volume defects inside the SZ and a more uniform deformation. The microstructural analysis results are corroborated by data acquired from microhardness and electrical conductivity studies, confirming the beneficial influence of modifying the tool's linear velocity on the material parameters. Findings: This study provides significant observations on the changes in microstructure and the generation of flaws throughout the process of FSP of AD31T alloy. These results have practical implications for improving the characteristics of the alloy and optimizing the production conditions. Originality/value: All samples exhibit a distinct reduction in electrical conductivity within the initial third of the sample, aligning with the transitional region between the base metal (BM) and the HAZ. This underscores the importance of understanding the transitional zones during FSP. [ABSTRACT FROM AUTHOR]

This study examines the impact of Friction Stir Processing (FSP) with TiO2 nanoparticle incorporation on the microstructural, mechanical, and tribological properties of AA5083 Metal Matrix Composites (MMCs). It offers a detailed analysis of the alterations in the alloy’s characteristics due to FSP. Microstructural examination was conducted using optical microscopy (OM) and scanning electron microscopy (SEM). Significant findings include the microstructural refinement where TiO2 nanoparticle addition during FSP shrank the grain size from 20 to 3 µm after one pass, which then rose to 7 µm following four passes. Mechanical properties, specifically microhardness and tensile strength, were assessed. Results indicated that after four FSP passes, the material can reach a yield strength of 192 MPa and an ultimate tensile strength (UTS) of 359 MPa, alongside a consistent microhardness of 103 HV0.1. Furthermore, it was observed that increasing FSP passes enhances energy absorption, although it remains lower than that of the base material. Analysis of fracture and wear mechanisms has led to the conclusion that with more passes, fracture mechanisms transition to a mix of ductile and brittle behaviors, and the friction coefficient decreases by up to 22.95%. [ABSTRACT FROM AUTHOR]

Recycling of metals is becoming crucial from an economic and environmental point of view. The solid-state recycling process Continuous Friction Stir Extrusion was used to produce wires out of A356-T6 chips. The mechanical properties of the produced wires were explored by varying the main process parameters. Characterization involved Vickers hardness tests, tensile tests, grain size measurements, and fracture surface analysis. It has been found that it is possible to achieve 77 % of the Ultimate Tensile Strength (UTS) and 92 % of Vickers hardness with respect to the as-fabricated A356 alloy. The average grain size increases with the tool rotational with values ranging from about 9 µm to about 11 µm. A 3D dedicated numerical model was used to predict the distributions and histories of primary field variables, and to calculate the Piwnik-Plata parameter, fostering a more in-depth understanding of the process mechanics. This allows for the precise prediction of unacceptable product quality of the bonding when the Plata and Piwnik parameters are low. Predicted temperature close to the rotating tool should reach 400 °C while the cochlea temperature should be below 100 °C for sound wires production thus avoiding early chip bonding and process failure. [ABSTRACT FROM AUTHOR]

The primary objective of this research work is to analyse the effect of double pass on grain refinement during friction stir processing (FSP). The impact of double pass was also assessed on the microstructure, micro-hardness, and tensile strength of the hybrid reinforced aluminum alloy. Field emission scanning microscopy with energy dispersive spectroscopic analysis was used to analyze the grain size distribution as well as the percentage of elements present across the stir zone (SZ) and mode of fracture during the tensile testing. Results show a notable increase in mechanical properties and a huge reduction in grain size when compared to base material (BM). The grain size of SZ in single pass FSP (FSPed-SP) and double pass FSP (FSPed-DP) was reduced to 76.71% and 91.8% in comparison to the BM because repetitive stirring action causes huge dynamic recrystallization. However, peak micro-hardness in FSPed-DP and FSPed-SP was achieved as 30.58% and 22.79% of the BM due to the hall–petch effect. FSPed-DP demonstrated superior ultimate tensile strength and percentage of elongation in contrast to FSPed-SP, which exhibited values of 29.03% and 25% respectively. [ABSTRACT FROM AUTHOR]

The increasing demand for lightweight and high-performance materials aimed at reducing carbon footprints necessitates the development of innovative technologies. In this study, high-strength carbon fibre (CF) was utilized to reinforce the aluminium (Al) matrix for fabricating the metal matrix composite (MMC). It was found that strain, strain rate and temperature gradient play a significant role in non-uniform particle distribution at the advancing and retreating sides of the processed regions. To address these challenges, Upward Friction Stir Processing (UFSP) with a threaded pin tool was proposed to assess the uniformity of the reinforcing carbon fibres on the advancing and retreating sides, which is the novelty in this study. The influence of UFSP tool offset direction on material flow characteristics and particle distribution were analyzed. Carbon fibre agglomeration and band formation within the metal matrix was given special attention during UFSP technique. A double-pass UFSP was introduced which revealed a homogenous dispersion of CF upon microstructural characterisation. Furthermore, results demonstrated a 36% increase in bulk hardness and 54% increase of electrical conductivity compared to base metal. Thus, incorporation of a 2 wt% of CF yielded harder and better electrically conductive UFSP-ed metal matrix composite. This is expected to have a wider application in industrial joining methods while joining of two dissimilar metals or metal based composites. [ABSTRACT FROM AUTHOR]

AbstractThe motive of this research is to fabricate AA7475/B4C/Al2O3 hybrid surface composites (HSCs) using friction stir processing (FSP) for various applications in aerospace, marine, and automotive industries. The research systematically varied key processing variables, including rotational speed (900–1300 rpm), feed rate (30–60 mm/min), and reinforcement ratios (from 30% B4C and 70% Al2O3 to 70% B4C and 30% Al2O3), to optimize responses such as ultimate tensile strength (UTS), tensile elongation (TE), and microhardness (MH). A face-centered central composite design (FCCCD) of response surface methodology (RSM) was employed to develop mathematical models correlating the input parameters with the response variables. An analysis of variance (ANOVA) was conducted to assess the effects and interactions of the processing parameters on the composite properties. A validation test confirmed the reliability of these optimal conditions. ANOVA results indicated that the tool rotational speeds had the most significant effect on the tensile, ductility, and hardness properties of the HSCs. However, changes in feed rate and reinforcement ratio had minimal impact on these properties. The study identified optimal conditions for different responses: UTS of 452.62 MPa, TE of 6.89%, and MH of 168.52 HV at a rotational speed of 1300 rpm, feed rate of 45 mm/min, and a 50:50% reinforcement ratio (50% B4C and 50% Al2O3). The HSCs fabricated at 1300 rpm, 45 mm/min, and a 50:50% reinforcement ratio exhibited significant necking before failure, leading to a ductile failure mode. [ABSTRACT FROM AUTHOR]

Friction stir welding of cast and rolled-state aluminum matrix composites is extensively used in many industries, and the speed at which the mixture is stirred profoundly influences the structure and characteristics of the welded connections. The present study investigates the microstructure and mechanical properties of the as-cast and as-rolled (ZrB2 + Al3Zr) particle-reinforced aluminum matrix composites. The welded joints were subjected to friction stir welding at a welding speed of 60 mm/min and stirring speeds of 1000, 1200, and 1400 rpm, separately. At a rotational speed of 1200 rpm, the welded joints exhibit optimal performance with an average hardness of 71.07 HV, a tensile strength of 183.9 Mpa, and an elongation of 16.7%. The weld core region generates precisely shaped equiaxed grains, while the weld matrix facilitates a significant amount of dislocation entanglement. At a rotational speed of 1200 rpm, the grain refinement effect is fully optimized, resulting in an average grain size of 2.94 μm. The recrystallized organization accounts for 70.6% of the grain size. Both types of reinforcing particles are adequately crushed, with the smallest particle size of ZrB2 particles being less than 100 nm and the smallest particle size of Al3Zr particles being less than 1 μm. The two methods of weld reinforcement are fine crystal strengthening and Orowan strengthening. [ABSTRACT FROM AUTHOR]

Aluminium metal matrix composites are widely used in automotive, aerospace, marine, and structural engineering due to their high strength-to-weight ratio and superior mechanical properties. Optimizing friction stir process parameters is critical to enhancing the performance of these materials. This study investigates the effects of FSP parameters such as rotational speed, tilt angle, and traverse speed, on the mechanical properties of AA5083/Silicon carbide and AA5083/Coal composites. Using a Taguchi L9 design of experiments, signal-to-noise ratio, and analysis of variance, this study identifies the optimal process settings for maximizing ultimate tensile strength, microhardness, and elongation. From the results, the study revealed that for AA5083/Silicon carbide composites, rotational speed was the most significant factor affecting tensile strength, while for AA5083/Coal composites, tilt angle played a more critical role. Rotational speed consistently influenced microhardness and elongation for both materials. The signal-to-noise ratio analysis indicates that optimal FSP parameters vary depending on the reinforcement material used. This study highlights the importance of tailoring FSP settings to specific reinforcements to achieve optimal mechanical properties. These findings contribute to the advancement of friction stir processing techniques for fabricating high-performance aluminium metal matrix composites, particularly for applications in industries requiring strong, lightweight, and corrosion-resistant materials. [ABSTRACT FROM AUTHOR]

AbstractThe development of friction stir welding (FSW) created the basic foundation for friction stir processing (FSP). This process entails refining the local microstructure and achieving the localised plastic deformation due to the stirring effect of the tool, which may involve adding additional filler material as required. The rotating tool involved in the process has a shoulder and pin responsible for heat generation for plastic deformation and localised mixing. The rotating tool is inserted and traversed on the desired surface, tailoring the material properties. The tool’s exposure to the surface causes localised plastic deformation and thermal gradient, and microstructural changes occur locally. The present investigation uses Friction Stir Processing (FSP) to fabricate an aluminium metal matrix composite. Recently, the use of aluminium alloy has been replaced by composites because of their increased mechanical and physical properties (specific properties). The experiment leads to manufacturing an aluminium metal matrix composite using aluminium oxide, boron carbide and commercially pure copper dust. Later, the effect of heat treatment on the respective metal matrix composite is studied. A comparative study among three different types of FSP techniques viz. FSP, Reinforced FSP, and Heat-treated Reinforced FSP have been performed. The tool revolution speed (RPM) and tool traverse speed of 400 RPM and 10 mm/min had been implemented, respectively. The T4 Heat-Treatment cycle was used during the current investigation. This investigative study was performed to analyse the changes in grain sizes and hardness values at the stir zone (SZ), thermo-mechanically affected zone (TMAZ), heat affected zone (HAZ) and on the base materials (BM) of the samples. The reinforced FSP metal matrix composite (MMC) showed an 81.26% increase in the micro-hardness value (HV) compared to the base metal. Further on analysing the microstructures, the reinforced FSP composite showed a 65.20% reduction in grain size. Moreover, the Heat-Treated sample showed an increase in the micro-hardness value by 99.8%. [ABSTRACT FROM AUTHOR]

This document is a summary of a special issue of the journal "Materials" titled "Development of Advanced Aluminum and Magnesium Alloys: Microstructure, Mechanical Properties and Processing." The special issue focuses on the latest progress in the development of advanced aluminum alloys, magnesium alloys, and their composites. Thirteen articles are included in the special issue, with six papers on aluminum alloys, two papers on magnesium alloys, and five papers on light metal composite materials. The articles cover a range of topics including optimization of aluminum alloys for casting processes, the effect of torch angle on the properties of aluminum alloys fabricated using additive manufacturing, and the development of high-strength aluminum metal-matrix composites. The special issue provides valuable insights into the relationships between microstructure, mechanical properties, and processing conditions, and aims to contribute to the future development and industrial applications of lightweight alloys. [Extracted from the article]

The present study investigated the effect of incorporating Yttria-Stabilized Zirconia (YSZ) and copper (Cu) in the development of Titanium-Based Metal Matrix Composites (TMCs) using the Friction Stir Processing (FSP) technique. The macrostructure of the TMCs, after adding 5% YSZ and 2% Cu, displayed a defect-free, crack-free, and porosity-free surface, indicating the precision of the FSP method. Microstructure analysis revealed a uniform distribution of reinforcement particles and proper dispersion of grains, key for enhancing mechanical properties. The interfacial bonding between titanium and YSZ was exceptionally strong, devoid of cracks and porosity, attributed to the copper additive's role. The increase in the number of grains per square inch for the Ti/5% YSZ/2% Cu composite (1176.26 grains per square inch at 500×) signified finer grain structure, contributing to a remarkable 48.04% improvement in tensile strength compared to pure titanium. The uniform distribution of reinforcement and strong bonding between titanium and YSZ are the driving forces behind the 46.34% increased in hardness. Additionally, the wear resistance of the composite improved by approximately 76.66%, a vital characteristic for applications facing abrasive conditions. The corrosion testing demonstrated an 8.33% enhancement in corrosion resistance with the Ti/5% YSZ/2% Cu composite. [ABSTRACT FROM AUTHOR]

The present work aims to elucidate the mechanism of microstructural evolution in different regions of nano-SiC particles reinforced aluminum matrix composites prepared by friction stir processing (FSP) on its electrochemical behavior. Electron backscatter diffraction technique (EBSD) and transmission electron microscopy (TEM) were employed to characterize the microstructure evolution of stir zone (SZ), advancing side thermomechanically affected zone (AS-TMAZ), retreating side thermomechanically affected zone (RS-TMAZ) and base metal (BM). The electrochemical behaviors of the above zones were investigated using electrochemical tests. A homogeneous and fine microstructure is formed in SZ, not only the nano-SiC is homogeneously distributed within the grains with an average grain size of 3.5 μm, but also the recrystallized grains account for the highest percentage of 85 %. The potentiodynamic polarization curve indicates that the corrosion current densities of the BM, RS-TMAZ, AS-TMAZ and SZ are 0.89, 0.39, 0.85 and 0.36 μA/cm2, respectively, while the polarization impedances are 33.40, 51.42, 48.72 and 73.79 kΩ cm2, respectively. Combining the Nyquist and Bode plots analysis, the optimal electrochemical corrosion resistance is in SZ. The fine and homogeneous recrystallized grains in SZ significantly improve its electrochemical corrosion resistance. This is mainly ascribed to the increase in crystal defects as a result of the increase in grain boundaries, elevating the electron scattering. Simultaneously, the increase in high-energy state grain boundaries is beneficial to the rapid formation of a thicker passivation film. [ABSTRACT FROM AUTHOR]

In the present study, considering the features and advantages of solid-state welding methods as compared with fusion welding methods such as arc welding, laser welding induction welding, and solid-state welding, they are used to connect CK45 steel to AISIS 304L steel to achieve the desired mechanical and metallurgical properties through experimental and practical tests, by trial and error, suitable parameters of distance, depth, and advance are obtained for welding, and finally a healthy and desirable weld is obtained. The purpose of the present study is to evaluate the weldability of CK45 steel to AISIS 304L steel by friction stir welding method. The distance, advance, and penetration depth parameters were experimentally determined as 950 rpm, 24 mm/min, and 0.35 mm, respectively, to obtain a healthy weld in terms of appearance. Then, through mechanical and metallurgical tests, the effect of the input parameters on the friction stir welding process was determined. The mechanical and metallurgical properties were also evaluated. The results show that the structure of the onion rings in the welding area is caused by the friction stir welding process, which is caused by the massive plastic deformation and the heat generated during the process. The scanning electron microscope image of the welded section of the steel sample shows the formation of a pearlite structure. Considering the severe plastic deformation and dynamic recrystallization in the friction stir welding process, the results obtained from the welding of dissimilar CK5 and AISI304 L show better mechanical properties and acceptable strength. [ABSTRACT FROM AUTHOR]

Friction Stir Processing (FSP) has become a famous solid‐state technology for the fabrication of a wide range of aluminum alloy‐based composites that today find multiple applications across the various metal industries. Generation of revolving, ribbon, bulk, excessive or mass flash as it is generally termed has been a common problem in numerous FSP works. When confronted by this challenge, many researchers apply different experimental and numerical modeling approaches or strategies to reduce the mass flash to practically acceptable limits since it often leads to undesirable loss of material and is also an unwanted defect. This subject is deficiently reviewed, and it therefore becomes the thrust of this paper, to investigate the common trends in mass flash generation during FSP and its commonly employed reduction strategies. Mass flash is caused by high rotational speed at low travel speed and vice versa, flat shoulder, no and low tilt angles, high plunge depth, axial force, and travel force. Mass flash causes material loss, loss of volume fraction control target, material thinning, and leads to poor quality fabrications. Mass flash reduction strategies include the use of high tool tilt angles, concaved tool shoulder, proportional rotational speed and travel speed, and optimal plunge depth, axial force and travel speed as supported by both the experimental and numerical modeling studies. [ABSTRACT FROM AUTHOR]

This study investigates the impact of friction stir processing (FSP) on the hydrogen embrittlement (HE) in AA6082-T6 heat-treatable aluminum alloy. The effects of different number of FSP passes and different hydrogen cathodic charging (HCC) conditions on the material's response to HE are examined through comprehensive mechanical testing, microhardness analysis, and microstructural characterization. The results revealed that FSP leads to a decrease in yield strength, ultimate tensile strength, and microhardness, accompanied by an increase in energy absorption. The introduction of hydrogen through HCC significantly reduces mechanical properties, particularly in non-FSPed specimens. Notably, specimens with 8 FSP passes exhibit an interesting behavior with a slight increase in energy absorption and microhardness values after HCC. Microstructural analysis shows that FSP refines the microstructure, resulting in enhanced resistance to hydrogen-induced blistering effects. These findings contribute to the understanding of hydrogen embrittlement in FSPed aluminum alloys, providing insights for developing surface-modified materials suited for hydrogen-rich applications. [ABSTRACT FROM AUTHOR]

This work presents surface nanocomposites of aluminum alloy AA1050, reinforced with zirconium oxide (ZrO2) nanoparticles developed through multipass friction stir processing (FSP). This article attempts to study the effects of the number of passes on the wear rate, microhardness profile, tensile properties, and macrostructure of surface nanocomposites. The results demonstrate that an improved distribution of ZrO2 nanoparticles is obtained following each FSP pass, and that the number of passes increases with a decrease in stir zone (SZ) grain size. Consequently, it was found that applying FSP passes continuously enhances the materials' microhardness and tensile characteristics. In the microstructure development of the stir zone during the ZrO2 nanoparticle FSP, dynamic recrystallization (DRX) was an essential mechanism. The main reason for this is that surface nanocomposites with homogenous ZrO2 particle dispersion and no discernible particle clustering in the stir zone were shown by microstructural studies conducted through FSP, which significantly reduced the matrix grain size. The AA1050 base metal (BM) has an ultimate tensile strength, yield strength, and hardness of 59.2 MPa, 24 MPa, and 30.1 respectively. The nanocomposite generated by 5 FSP passes exhibits improved yield stress (55 MPa), tensile strength (94.5 MPa), and microhardness (86.5 HV), but its tensile ductility decreased from 34% to 23.8% when compared to the base metal. Tensile strength that is higher is the outcome of fine dimples' ability to pin the dislocation movement during tensile loading. According to fractographic studies, the ductile–brittle mode replaced the dimple-shaped ductile fracture mode.Highlights: ZrO2/AA1050 surface nanocomposites were produced by multipass FSP. Significant strength and microhardness are demonstrated by the ZrO2 nanoparticle reinforcement build, along with a refined microstructure. The results demonstrate the potential of FSP in producing composite materials for specific functional requirements. [ABSTRACT FROM AUTHOR]

The main objective of this study was to optimize the friction stir process parameters to fabricate agate particle reinforced AA6061-T6 Aluminum alloy surface composite for hardness and tensile strength. The surface composite samples were made using a CNC milling machine based on Taguchi's mixed L16 orthogonal array. The process parameters such as tool rotational speed, traverse speed, percent of reinforcement, number of passes and pin profiles were selected in this study. The optimal properties for the developed surface composite were obtained when surface composites having 18% reinforcement were fabricated by a two-pass FSP using a squared pin tool with a rotational speed of 1400 rpm and traverse speed of 60 mm/min. At the optimal process parameters, the tensile strength and hardness of the fabricated surface composite were found to be 312.23 MPa and 74.82 HRB respectively. ANOVA analysis performed at a 95% confidence level revealed that all process parameters were significant and the contribution of the number of passes on the properties of surface composite was higher than other process parameters. Microstructural analysis revealed that medium rotational speed and high traverse speed produced a uniform distribution of agate particles which helped to improve the properties. Article Highlights: A new aluminum alloy surface composite produced with friction stir processing. Studied the effects of process parameters on tensile strength and hardness of the surface composite. Grey relational analysis (GRA) identified the best process parameters for optimum properties. [ABSTRACT FROM AUTHOR]

Metal matrix composites (MMCs) are essential materials in various industries due to superior properties, such as high strength-to-weight ratios, better corrosion resistance, improved wear resistance and adaptability, developed by continuous improvements in their fabrication methods. This helps to meet the growing demand for high-performance and sustainable products. The industries that stand to gain the most are automotive and aerospace, where MMCs are used for car parts, airplane frames, and jet engines that need to be strong and lightweight. Furthermore, MMCs are being extensively used in the biomedical industry for implants and medical equipment because of their suitable mechanical integrity and corrosion resistance. Applications in heavy construction, defense, and even space exploration are noteworthy. The advancements in fabrication of MMCs have revolutionized the composite industry with their improved mechanical, tribological, and metallurgical properties. This review article offers an introduction and thorough examination of the most recent advancements (mostly within the last five years) in fabrication methods of MMCs. The novelty and modernization in the traditional processes and advanced processes are covered, along with discussing the process parameters' effects on the microstructure and properties of the composites. The review focuses on features and prospective applications of MMCs that have been greatly improved and extended due to such advancements. The most recent methods for developing MMCs, including friction stir processing (FSP), ultrasonic-assisted stir casting, and additive manufacturing, are discussed. Artificial intelligence and machine learning interventions for composite manufacturing are also included in this review. This article aims to assist researchers and scholars and encourage them to conduct future research and pursue innovations to establish the field further. [ABSTRACT FROM AUTHOR]

In this study, the environmentally friendly friction stir processing (FSP) method was utilized to fabricate surface composites employing technical aluminum matrix 1050-H14 and aluminum alloy 6060-T4 reinforced with silicon carbide (SiC) particles. Microstructure analysis, employing light and scanning electron microscopy, in conjunction with comprehensive evaluations of hardness, compressive strength, and tribological properties, was conducted to elucidate significant findings. The results reveal that an augmented number of FSP passes contributes to the homogenization of microstructure, leading to the alteration of SiC particle morphology and fragmentation. Consequently, this phenomenon results in improved mechanical properties, particularly noteworthy in the case of AA6060-T4 alloy matrix composites, and enhanced wear resistance. Both AA1050-SiC and AA6060-SiC composites demonstrate notable increases in compressive strength compared to their unreinforced matrices. Particularly noteworthy is the substantial enhancement in compressive strength observed in the AA6060-SiCp composite, escalating from 249 to 331 MPa (at ε = 0.1) and from 398 to 715 MPa (at ε = 0.2) with an increase in the number of FSP passes. Additionally, FSP's ability to precisely control process parameters such as tool rotational speed and traverse speed allows for the optimization of mechanical properties and microstructural characteristics tailored to specific application requirements. This study highlights the potential of FSP in fabricating high-performance aluminum matrix composites with superior strength and wear resistance, positioning it as a viable technique for advanced engineering applications. The environmentally friendly nature of FSP, due to its solid-state operation and reduced energy consumption, further underscores its suitability for sustainable manufacturing practices. [ABSTRACT FROM AUTHOR]

The in situ Al-Cu composites were manufactured by powder metallurgy with state-of-the-art microwave sintering tailed by friction stir process in two different ways: unidirectional overlapped two-pass and unidirectional flipped two-pass. Novelty is claimed in the flipped process. An attempt was made to investigate the addition of copper beyond the solubility limit and the critical composition of an Al-Cu alloy (4.6 wt.%). The overlapped process enforced higher temperature, cumulative strain, and strain rate. Since Al and Cu are high-stacking fault energy metals, both dynamic recrystallization and dynamic recovery occurred and resulted in grain refinement and higher fractions of Al2Cu. The self-hard and brittle nature of Cu and Al2Cu improved strength (Al-3wt.%Cu, 231.23 MPa), hardness (Al-6wt.%Cu, 82.5 HV), and deteriorated ductility (Al-7wt.%Cu, 5.2%). The formed Al2Cu at the interface were surrounded by Al particles and formed passive films Al2O3 and Cu2O enhanced corrosion resistance (Al-5wt.%Cu, 0.00717191 mpy). The process densely compacted the material, minimized porosity, decreased dislocation density, and increased strain aided in better electrical conductivity (Al-5wt.%Cu, 145.92%IACS). The flipped process circumvented excessive heating and embrittlement of the material thereby improving strength without loss of ductility (Al-7wt.%Cu, 235.85 MPa and 25.53%). Al-3wt.%Cu with minimum corrosion current (5.681 µA/cm2) exhibited maximum resistance to corrosion (0.169852 mpy). The highest electrical conductivity was noticed for (Al-5wt.%Cu, 104.17%IACS). [ABSTRACT FROM AUTHOR]

Al6061 alloy has become prevalent in the industrial sector because of its low density, excellent machinability, and corrosion resistance but it lacks properties like hardness and wear. Therefore, surface modifications by friction stir processing (FSP) are done with additive nanosized particles like multi-walled carbon nanotubes (MWCNT), Titanium oxide (TiO2), and Graphene nanoparticles (GNP) To perform 2-pass FSP, a uniquely engineered fixture with coolant circulated underneath the plate at sub-zero temperatures is used. Grain refinement has been observed in micrographs as a consequence of 2-pass FSP. The coolant circulated beneath carries the heat generated and enhances the heat dispersion rate, culminating in finer grains. The calculated mean grain size of the Al6061 alloy was considerably decreased in all the surface composites. There is a substantial improvement in the microhardness profile, which has increased by nearly 70–90%, as well as a significant enhancement in tensile strength of almost 20–30% in all the composites. The ductile type of failure during tensile load is revealed by SEM fractography. The process of dynamic recrystallisation is responsible for the development of equiaxed grains. The wear resistance of all the composites is also enhanced, and the COF of Al6061/GNP composite is found to be lowest at 0.23. [ABSTRACT FROM AUTHOR]

This study explored the effect of friction stir processing (FSP) on tungsten inert gas (TIG)-welded AA6061-T6 and AA7075-T6 joints by utilizing three different tool pin geometries, namely simple cylinder (SC), threaded cylinder with triflat faces (THF), and simple square (SS). The metallurgical aspects of unprocessed and processed weld regions were analyzed and correlated with the ultimate tensile strength, impact toughness, and microhardness properties. Results revealed that the post-FSP with a THF pin transformed the coarse dendritic structures (AGS of 34.55 µm) of the TIG weld into equiaxed fine structures (AGS of 3.51 µm) and increased the UTS, impact toughness, and microhardness by 71.51%, 95.40%, and 72.46%, respectively. The joint processed with the THF pin resulted in the highest ultimate tensile strength of 279 MPa, impact toughness of 15.02 J, and microhardness of 116.13 HV in the nugget region compared to the other two pin geometries. The highest joint properties of THF pin were attributed to the formation of fine grain structures in the nugget region, high effective strain and heat generation, improved material flow, and the decimation of intermetallic precipitates with their uniform dispersion in the nugget region. The tensile fractured surface of the TIG weldment had noticeable macro voids and coarse dimples with some rough cleavage facet in the fusion region, resulting in a brittle mode of failure. However, the tensile fractured surface of TIG + FSP weldments showed ductile failure due to the presence of fine and deep dimples with tear ridges without any void. [ABSTRACT FROM AUTHOR]

The research of hybrid composites' machinability is an intricate modern trend. Industries then evaluate the surface finish of the machined surfaces to ensure they are up to snuff with the needs of the applications. Therefore, the purpose of this research is to examine the machinability performance of AA8014 workpieces (welded by friction stir processing (FSP) with hybrid reinforcement of Titanium diboride and Zirconium dioxide at CNC vertical milling centre, including material removal rate and surface finish (surface roughness). By changing the reinforcement percentage from 4 to 10%, the tool rotational speed from 1000 to 1600 rpm, the traverse speed of the tool head from 4 mm/min setting to 5 mm/min setting, and the axial force from 3 to 4 kN at four levels, we were able to weld the samples with 16 different combinations (L16 orthogonal array) of FSP parameters settings. Taguchi analysis and planning were used to optimize the pace of material removal and smooth out the surface. After milling, the weldment's maximum material removal rate was measured at 2.48 mm3/min, and its minimum surface roughness was measured at 1.84 m. [ABSTRACT FROM AUTHOR]

The purpose of this study is to develop brass based composites using friction stir processing (FSP) for improved wear resistance. SiC particles (volume percentage of 0–18) were efficiently reinforced into Cu−40Zn dual phase brass using FSP. A tool rotational speed of 1600 rpm and a traverse speed of 60 mm/min were used. The FSP process provided an excellent distribution of SiC particles without aggression and segregation. The solid state processing subdued the role of density gradient to have an adverse effect on particle distribution. EBSD maps demonstrated extreme refinement of grains because of dynamic recrystallisation. TEM micrographs hinted that the dynamic recrystallisation was interrupted i.e. discontinuous. Few dislocation fields as well as twinned grains were spotted. SiC particles were beneficial to improve the resistance to wear of the brass composite. Further, the role of SiC particles on the mode of sliding wear as well as the size of wear debris was reported. [ABSTRACT FROM AUTHOR]

Commercial pure cast magnesium (Mg) was subjected to friction stir processing (FSP) at a rotational speed of 600 rpm and tool traverse speed of 60 mm/min. The samples extracted from cast Mg and friction stir processed magnesium have been analysed for the microstructure, hardness, and temperature-dependent damping capacity. The average grain size of as cast pure Mg is reduced from 780 to 26 μm after FSP. There is about a 15% increase in hardness after FSP. The dynamic mechanical analyser (DMA) measured the damping capacity using a three-point bending mode. The FSPed Mg sample exhibited 50% lower damping capacity than the cast Mg at room temperature. However, as the temperature increased, significantly above 80°C, the damping capacity of the FSPed magnesium was greater than that of the cast magnesium. At room temperature, the damping capacity of FSPed Mg was decreased because of the formation of tangled dislocations. In contrast, the increase in damping capacity above 80°C was due to the increased grain boundary area. [ABSTRACT FROM AUTHOR]

This document is an editorial from the journal "Crystals" that provides an overview of recent developments in additive manufacturing (AM) and highlights the studies featured in a special issue of the journal. The studies cover various aspects of AM, including laser additive manufacturing, electrodeposition, and fused filament fabrication, and explore innovations in material properties, microstructural control, and overall performance. The editorial also identifies existing knowledge gaps in AM and suggests future research directions, such as multi-material AM techniques, advanced simulation and modeling tools, scalability, sustainability, and long-term durability and performance studies. The document emphasizes the importance of continued research in these areas to fully realize the potential of AM and drive industrial innovation. [Extracted from the article]

The AA7075 high-strength aluminum alloy exhibits a pronounced tendency for hot cracking during fusion welding, which hampers its widespread utilization in lightweight design concepts. This study aims to investigate the effectiveness of friction stir processing (FSP) as a pre-weld treatment to eliminate the occurrence of hot cracking during fusion welding of the AA7075 aluminum alloy. Our findings demonstrate that the FSP pre-weld treatment successfully suppresses liquation cracking in the AA7075 alloy, even when utilizing ER1050 filler metal for welding, which poses a considerable risk of liquation cracking. The FSP treatment induces a transformative effect on the microstructure of the hot-rolled material, leading to the conversion of the typical large elongated pancake-shaped grains into refined recrystallized grains. Electron backscatter diffraction (EBSD) analysis confirms the introduction of finer grains, characterized by an increased grain boundary area, and higher volume fraction of low angle grain boundaries within the partially melted zone (PMZ) of the friction stir processed base metal. This leads to a reduction in the thickness of the liquid film and consequently diminishes the susceptibility to liquation cracking. These findings prove that arc welding with FSP pre-weld treatment is an enabling welding strategy for producing high-performance AA7075 joints. [ABSTRACT FROM AUTHOR]

High strength-ductility synergy is difficult to achieve in Nb alloys. Although high strength has been achieved through severe plastic deformation (SPD) technology, led to low ductility in alloys. In this work, FSP technology was applied to treat Nb–5W–2Mo–1Zr-0.1C (Nb521) alloys in preparation of fine-grained (FG)/ultrafine-grained (UFG) Nb521 with excellent strength and ductility. The microstructure evolution and mechanical property improvement mechanism were systematically studied for Nb521 alloy through various characterization pathways. The research results indicated that UFG Nb521 alloy with a grain size of 0.63 ± 0.41 μm can be prepared using low shoulder plunge depth FSP (LPD-FSP), which is the first report of UFG Nb521 alloy. The main reason for the formation of onion rings structure in SZ is the periodic wear of the stirring tool, and the onion rings structure does not cause mechanical damage. The texture formed by Nb521 alloy under different processing parameters is off-axis shear texture, which matches the ideal shear texture of D2 (112‾)[111] after rotation. In addition, this study also elaborated on the refinement mechanism of the second phase particles (Nb, Zr) C in Nb521 alloy during FSP. This study also indicated that the increase in yield strength of FSP samples at room temperature is mainly determined by grain refinement. These findings provided new ideas for the development of high-performance niobium alloys.

Magnesium alloys, noted for their substantial mechanical strength and exceptional biocompatibility, are increasingly being considered for use in biodegradable implants. However, their rapid degradation and significant hydrogen release have limited their applications in orthopaedics. In this study, a novel Mg-RE-Sr alloy was created by friction stir processing to modify its microstructure and enhance its degradation performance. Through microstructural characterization, the friction stir processing effectively refined the grains, accelerated the re-dissolution of precipitates, and ensured a uniform distribution of these phases. The processed alloy demonstrated improved comprehensive properties, with an in vitro corrosion rate of approximately 0.4 mm/y and increases in ultimate tensile strength and elongation by 37 % and 166 %, respectively. Notably, in vivo experiments involving a rat subcutaneous implantation model revealed a slower degradation rate of 0.09 mm/y and a uniform degradation process, basically achieving the requirements for ideal performance in orthopaedic applications. The superior degradation characteristics were attributed to the synergistic effect of attenuated galvanic corrosion and the formation of a dense Y(OH)3/Y2O3 film induced by an exceptional microstructure with a highly solid-soluted matrix and uniformly refined precipitates. Meanwhile, the alloys exhibited excellent biocompatibility and did not cause undesirable inflammation or produce toxic degradation products. These improvements in biocompatibility and degradation characteristics indicate great promise for the use of this friction stir processed alloy in osteosynthesis systems in the clinical setting.

Improving the degradation performance and enhancing the biocompatibility are the main challenges of Mg-based biodegradable implants. In this study, a nano-hydroxyapatite-enhanced (nHA) Mg matrix composite was fabricated via friction stir processing and characterised, including microstructure, mechanical, in vitro degradation properties, and cytocompatibility. Hydroxyapatite is renowned for its superior bone compatibility, promoting healing responses and tissue growth. Friction stirring created a gradient grain structure in the alloy, with the stir zone exhibiting the highest grain refinement. The stir zone also contained most of the incorporated nHA and exhibited a strong texture with grains preferentially oriented along the [0001] direction. Immersion and polarisation experiments showed an increase in the FSPed WE43-nHA's corrosion resistance due to the refined microstructure. The treatment also caused a shift in the corrosion mode of the alloy from localized to uniform corrosion despite some localized corrosion associated with the nHA. Cytocompatibility tests in human osteoblast (HOB) cell lines indicated good biocompatibility in the Mg-nHA alloy, with cells exhibiting relatively healthy morphology and increased live cell count. Friction stir processing is a viable manufacturing option for creating Mg-based metal matrix composites with improved corrosion resistance and good biocompatibility.

High-entropy alloys (HEAs) present unique advantages in surface modification due to their stable mixed-state structures and resistance to intermetallic compound formation. This study investigates the surface modification behavior of equiatomic TiNbHfZnZr HEA components in Ti6Al4V alloy using friction stir processing (FSP). The aim is to enhance the mechanical properties and structural stability of Ti6Al4V by incorporating HEA elements. It was found that the introduction of high-entropy alloys forms shear bands with distinctive micro and nano gradient structures on the surface of the Ti6Al4V alloy. These shear bands not only significantly refine the grains but also promote β phase and β twin formation. The HEA-induced shear bands enhance the strength and stability of the alloy by creating bcc twins and dislocation networks that suppress martensitic transformation and maintain superelasticity. Concurrently, the introduction of HEA components leads to the formation of stable dual-phase (α + bcc) microstructures within the α matrix, significantly improving hardness and modulus.

Abstract The primary objective of this study is to investigate the microstructural, mechanical, and wear behaviour of AZ31/TiC surface composites fabricated through friction stir processing (FSP). TiC particles are reinforced onto the surface of AZ31 magnesium alloy to enhance its mechanical properties for demanding industrial applications. The FSP technique is employed to achieve a uniform dispersion of TiC particles and grain refinement in the surface composite. Microstructural characterization, mechanical testing (hardness and tensile strength), and wear behaviour evaluation under different operating conditions are performed. Response surface methodology (RSM) is utilized to optimize the wear rate by considering the effects of process parameters. The results reveal a significant improvement in hardness (41.3%) and tensile strength (39.1%) of the FSP-TiC composite compared to the base alloy, attributed to the refined grain structure (6–10 μm) and uniform distribution of TiC particles. The proposed regression model accurately predicts the wear rate, with a confirmation test validating an error percentage within ± 4%. Worn surface analysis elucidates the wear mechanisms, such as shallow grooves, delamination, and oxide layer formation, influenced by the applied load, sliding distance, and sliding velocity. The enhanced mechanical properties and wear resistance are attributed to the synergistic effects of grain refinement, particle-accelerated nucleation, the barrier effect of TiC particles, and improved interfacial bonding achieved through FSP. The optimized FSP-TiC composites exhibit potential for applications in industries demanding high strength, hardness, and wear resistance.

Abstract Present study has been conducted to characterize the Mg alloy namely AZ31-based composite joined by Friction stir processing (FSP) technique. This study deals with the effect of single and double passes in FSP of AZ31 Mg alloy. The single pass run in FSP is followed at tool rotation speed (N) of 1000 to 1400 rpm. Also, the double pass run in FSP was followed at these speeds without using reinforcements. The feedstock particles namely SiC, Al2O3, Cr, and Si powders were used in fabrication process. The hardness, impact strength, and tensile strength characteristics were assessed in the stir region zone, and the results indicated significant improvement in these properties. The highest values of mechanical strength were seen in the FSPed area with N = 1000 rpm at a constant transverse speed (r) of 40 mm/min. Also, the tensile strength of the two passes FSPed plates is much higher than that of the single section without any reinforcement, as revealed in previous study also. The Scanning electron microscopy (SEM) analysis is done at two different magnifications for the Silicon carbide, Alumina, Chromium, and Silicon powder reinforced composites fabricated at speed of 1000 rpm. The microstructure shows that reinforced particles were uniform dispersed into FSPed region and agglomerated with Mg matrix. Si powder produces finer microstructure as compare to SiC, Al2O3, Cr. FSP decreases the grain size of processed material. Optical Microscopy results revealed that the reinforcement particle produced a homogenous microstructure and, a refined grain and equally dispersed in matrix material without split to the particle.

High-entropy alloys (HEAs) with a face-centered cubic (FCC) lattice exhibit remarkable work-hardenability and high fracture toughness at cryogenic temperatures. However, in some non-equiatomic FCC HEAs, grain boundary melting defects may form during the homogenization process, which may lead to embrittlement of the grain boundaries. To address this issue, in this study, we propose the use of friction stir processing (FSP) to tailor the microstructure of a typical non-equiatomic Fe40Mn27Ni26Co5Cr2 HEA. After FSP, the mechanical properties of the non-equiatomic Fe40Mn27Ni26Co5Cr2 HEA were substantially improved. The study revealed that the improved mechanical properties could be attributed to the intense thermal-shear effect of FSP, which simultaneously eliminated grain boundary segregation and induced discontinuous dynamic recrystallization to refine grain size. Our findings not only shed light on understanding the embrittlement mechanism of homogenization treatment in non-equiatomic FCC HEAs, but also provide a useful route to improve the mechanical properties of FCC HEAs.

Rising concerns about climate change drive the demand for lightweight components. Magnesium (Mg) alloys are highly valued for their low weight, making them increasingly important in various industries. Researchers focusing on enhancing the characteristics of Mg alloys and developing their Metal Matrix Composites (MMCs) have gained significant attention worldwide over the past decade, driven by the global shift towards lightweight materials. Friction Stir Processing (FSP) has emerged as a promising technique to enhance the properties of Mg alloys and produce Mg-MMCs. Initially, FSP adapted to refine grain size from the micro to the nano level and accelerated the development of MMCs due to its solid-state nature and the synergistic effects of microstructure refinement and reinforcement, improving strength, hardness, ductility, wear resistance, corrosion resistance, and fatigue strength. However, producing defect-free and sound FSPed Mg and Mg-MMCs requires addressing several variables and their interdependencies, which opens up a broad range of practical applications. Despite existing reviews on individual FSP of Mg, its alloys, and MMCs, an attempt has been made to analyze the latest research on these three aspects collectively to enhance the understanding, application, and effectiveness of FSP for Mg and its derivatives. This review article discusses the literature, classifies the importance of Mg alloys, provides a historical background, and explores developments and potential applications of FSPed Mg alloys. It focuses on novel fabrication methods, reinforcement strategies, machine and tool design parameters, material characterization, and integration with other methods for enhanced properties. The influence of process parameters and the emergence of defects are examined, along with specific applications in mono and hybrid composites and their microstructure evolution. The study identifies promising reinforcement materials and highlights research gaps in FSP for Mg alloys and MMCs production. It concludes with significant recommendations for further exploration, reflecting ongoing advancements in this field.

The machinability of aluminum alloy (Al-6082) has the scope of enhancement by integrating Friction Stir Processing (FSP) with tool geometry, tool shape and different tool materials. In this research, the role of tool pin shape has been studied by experimenting on various tool shapes (square, hexagonal and octagonal) with the aim of machinability improvement. In FSP, the tool rotation speed is 930rpm and tool travel speed is 26mm/min. The specimens have undergone tensile, microhardness and microstructure testing using optical microscope and scanning electron microscopy. The percentage elongation has been increased from 15% to 29% in the case of the octagonal-shaped tool pin; similarly, the (Vickers’) microhardness value is 14.6% higher than the square- and hexagonal-shaped tool pins. Among these tool pin shapes, the octagonal-shaped tool pin succeeded in providing the best-in-class machinability performance on Al-6082 T6 alloy with FSP. It may unveil the newer scopes of FSP on Al-6082 for automotive components assembly and other similar applications. [ABSTRACT FROM AUTHOR]

Graphene has been considered an ideal reinforcement in aluminum alloys with its high Young's modulus and fracture strength, which greatly expands the application range of aluminum alloys. However, the dispersion of graphene and the interfacial reaction between graphene and the aluminum matrix limit its application due to elevated temperature. Friction stirring processing (FSP) is regarded as a promising technique to prepare metal matrix composites at lower temperatures. In this paper, FSP was used to prepare graphene-nanoplates-reinforced aluminum composites (GNPs/Al). The corresponding effects of the process parameters and graphene content on GNPs/Al were thoroughly studied. The results showed that plastic strain, heat input, and graphene content were the key influencing factors. Large degrees of plastic strain can enhance the dispersion of graphene by increasing the number of stirring passes and the ratio of stirring to welding velocity, thereby improving the strength of GNPs/Al. Low heat input restricts the plastic flow of graphene in the matrix, whereas excessive heat input can promote interfacial reactions and lead to the formation of a more brittle phase, Al4C3. This is primarily associated with the stirring velocity and welding velocity. High graphene content levels can improve the material strength by refining the grain size, improving the load transfer ability, and acting as a precipitate to prevent dislocation movement. These findings make a contribution to the development of advanced aluminum alloys with graphene reinforcement, offering broader application potential in industries. [ABSTRACT FROM AUTHOR]

This study investigates the potential of employing ceramic particles (CrC, NbC, and TaC) and their combinations to enhance several properties of AA6061 aluminum alloy during friction stir processing (FSP). FSP greatly enhances the reduction in the grain size compared to the original metal. Adding ceramic particles to the material strengthens the resistance to grain growth; thus, FSP significantly reduced grain size compared to the base metal by an average of 91.98%. In particular, composites containing TaC and a combination of CrC and TaC have the smallest grain size, possibly due to the combined impacts of these materials. Nevertheless, there were difficulties in the dispersion of particles, as they tended to be distributed randomly during FSP. Adding ceramic particles can significantly decrease friction compared to the alloy without reinforcement, but the extent of the decrease depends on the type and amount of ceramic particles added. Hybrid composites consisting of CrC and TaC have the most minimal friction coefficient. This hybrid also demonstrated exceptional mechanical properties, with increased stiffness by 34.7% and shear strength by 34.1% compared to the base alloy. Microhardness was significantly enhanced by up to 55.90% with reinforcements, particularly in the CrC + TaC hybrid and TaC composites. The microhardness is improved substantially by including reinforcements, with the hybrid CrC + TaC composites and TaC demonstrating the most substantial gains. The results indicate that adding ceramic particles, specifically CrC and TaC, dramatically enhances the wear resistance, mechanical strength, and microstructural characteristics of the AA6061 aluminum alloy. [ABSTRACT FROM AUTHOR]

The primary objective of this study is to investigate the microstructural, mechanical, and wear behaviour of AZ31/TiC surface composites fabricated through friction stir processing (FSP). TiC particles are reinforced onto the surface of AZ31 magnesium alloy to enhance its mechanical properties for demanding industrial applications. The FSP technique is employed to achieve a uniform dispersion of TiC particles and grain refinement in the surface composite. Microstructural characterization, mechanical testing (hardness and tensile strength), and wear behaviour evaluation under different operating conditions are performed. Response surface methodology (RSM) is utilized to optimize the wear rate by considering the effects of process parameters. The results reveal a significant improvement in hardness (41.3%) and tensile strength (39.1%) of the FSP-TiC composite compared to the base alloy, attributed to the refined grain structure (6–10 μm) and uniform distribution of TiC particles. The proposed regression model accurately predicts the wear rate, with a confirmation test validating an error percentage within ± 4%. Worn surface analysis elucidates the wear mechanisms, such as shallow grooves, delamination, and oxide layer formation, influenced by the applied load, sliding distance, and sliding velocity. The enhanced mechanical properties and wear resistance are attributed to the synergistic effects of grain refinement, particle-accelerated nucleation, the barrier effect of TiC particles, and improved interfacial bonding achieved through FSP. The optimized FSP-TiC composites exhibit potential for applications in industries demanding high strength, hardness, and wear resistance. [ABSTRACT FROM AUTHOR]

The grain structure evolution and nanomechanical behavior of cold-sprayed Al coating on Ti substrate with friction stir spot processing (FSSP) were studied by the electron backscatter diffraction and nanoindentation methods. The low-angle boundaries (LAGBs) fraction and the density of the geometrically necessary dislocations (GNDs) decreased from the base zone (BZ) to the stir zone (SZ). The average grain size, the LAGBs fraction and the density of the GNDs were various in different locations of the SZ, which can be attributed to the variety of local shear strain and temperature gradient during FSSP. The B/ B - component, the C component, and the A*1/ A*2 component were mainly developed in the SZ. The highest intensity of the B/ B - component appeared in the 3/8D of the SZ, indicating that the plasticized materials flowed downward experienced the highest shear strain. The materials in the heat affected zone (HAZ) underwent static recrystallization, while the continuous dynamic recrystallization (CDRX) and the geometric dynamic recrystallization (GDRX) occurred in the thermo-mechanically affected zone (TMAZ) and SZ. The nano-hardness and elastic modulus of the cold-sprayed Al coating after FSSP were comparable to those of pure Al bulk. The grain size and dislocation density were the main factors affecting the nano-hardness in the SZ. [ABSTRACT FROM AUTHOR]

Tungsten (W) has a high melting point, excellent thermal conductivity, and irradiation resistance, making it the most promising plasma facing material for divertors in fusion reactors, which are currently under development. However, since the divertor is exposed to an extremely harsh environment, it is considered necessary to develop suitable and cost-effective repair techniques. In this study, the applicability of the atmospheric plasma spraying (APS) method using a gas shroud as a repair technique for W components was investigated, in particular the possibility of strengthening the repaired part by applying friction stir processing (FSP) as a post-treatment. It was found that the application of a gas shroud can suppress in-flight oxidation to some extent, even when the W is deposited in air. In addition, the FSP treatment reduced grain size and porosity, resulting in an increase in microhardness of approximately 37.5% compared to the base material (W substrate) and 203.5% compared to the as-sprayed material. The gas shroud APS and FSP post-treatments have been shown to have potential as repair techniques for tungsten components in future fusion reactors. [ABSTRACT FROM AUTHOR]

In the present work, grain‐refined WE43 magnesium alloy was produced by friction stir processing to investigate the in vitro degradation behavior targeted for temporary bone implant applications. Friction stir processing resulted in significant grain refinement (from 46±4.2 μm to 16.1±5.4 μm) as observed from microstructural studies. Increased wettability was observed from the contact angle measurements in grain‐refined WE43 alloy. The corrosion behavior of the base alloy and the grain refined alloy assessed by potentiodynamic polarization tests demonstrated the influence of the smaller grain size and decreased intermetallics on enhancing corrosion resistance. Immersion studies carried out in simulated body fluids for one week indicated a quick development of the protective magnesium hydroxide on the surface of grain‐refined WE43 alloy compared with the base alloy. The deposition of the mineral phases from the immersed solution on the surface of the samples was studied by scanning electron microscopy and x‐ray diffraction analysis to assess the effect of microstructure on the biomineralization. Promisingly, grain refined WE43 exhibited relatively excellent mineral deposition which further helped to control the degradation of the alloy. The weight loss measurements of the samples from the immersion tests were also in good agreement with the electrochemical test results. Hence, the results demonstrate the promising role of grain refinement by friction stir processing in tailoring WE43 magnesium alloy with better degradation behavior for temporary bone implant applications. [ABSTRACT FROM AUTHOR]

In this study, a bulk-area stirring zone (BSZ) was generated within the Al–Mg–Si alloy using friction stir processing with a combination of pin overlapping and water cooling. Detailed examinations were conducted on various aspects, including microstructural evolution, intermetallic behavior, crystallographic texture, and mechanical properties. The bulk-area stir zone (BSZ) microstructure contains an equiaxed fine-grained structure with more fraction of high-angle grain boundaries due to intense plastic straining and dynamic recrystallization. The grain refinement remained consistent across each overlapping pass, typically within the range of 3 to 4 µm. Notably, the BSZ exhibited the formation of A1-{111}(112) texture components with a maximum intensity of 5.4 owing to the material flow caused by the tool's revoluting nature around the pin. The hardness distribution across the BSZ was found to be uniform and aligned with the grain size values. The combined effects of material softening and intermetallic dissolution in the BSZ led to a substantial enhancement of 127% in ductility. [ABSTRACT FROM AUTHOR]

Hybrid lap joints of polypropylene (PP) and aluminum alloy AA5052 were fabricated using friction stir lap welding under different conditions of tool rotation speed, traverse speed and tilt angle, while placing PP on top. A full factorial design of experiments with three levels of each process parameter was performed, and the lap shear strength was evaluated for each run. The temperature at the interface between PP and AA5052 was measured by thermocouples, and an inverse heat conduction technique was utilized to estimate the approximate temperature distribution in PP. Cross sections of the joint were also examined using optical and scanning electron microscopy. It was found that decreasing the traverse speed, increasing the rotational speed and increasing the tilt angle resulted in an increase in the joint strength. These conditions also resulted in higher process temperatures, which lead to a more uniform weld nugget with less voids, due to the enhanced material flow. Moreover, morphology analysis revealed that mechanical interlocking caused by the anchoring of metal hooks in PP mainly contributed to the strength and performance of the joint. A direct relationship was found between the hook length on the advancing side and the lap shear strength. [ABSTRACT FROM AUTHOR]

Conventional welding processes destroy the unique microstructural characteristics in nanobainitic steels. A novel method, i.e. tailored friction stir welding (FSW) and postheat treatment, was employed to overcome this problem. The postprocessing austempering was carried out on friction stir welded high-carbon steel to obtain nanobainite, and obtained microstructural characteristics were compared to that achieved by simple isothermal bainite transformation. Bainitic sheaves and austenite microblocks could be achieved in both production procedures. However, bainitic ferrites and austenite films within the bainitic sheaves were thinner, and austenite microblocks were finer when implementing the post-processing heat treatment after FSW. FSW enhanced the hardness of the primary steel from 385 HV to above 800 HV, which was maintained at about 520 HV even after post-heat treatment, higher than that of after implementing the isothermal bainite transformation (490 HV). This achievement can be related to FSW that reduced the mean diameter of austenite blocks, the thickness of bainitic ferrite, and the thickness of austenite films from 3820, 138, and 122 nm to 2200, 92, and 78 nm, respectively. Moreover, the microstructure and hardness of various microstructural zones of friction stir welded sample before and after heat-treatment were analyzed and discussed in detail. The outcome of this study can be applied in academic and industrial areas to propose a cost-effective method to weld nanobainitic steels. [ABSTRACT FROM AUTHOR]