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AbstractThe present investigation focuses on the synthesis of mono (AA5052/SiC and AA5052/graphene) and hybrid (AA5052/SiC/graphene) surface composites using friction stir processing (FSP). This work examines the synergistic effect of SiC and graphene on the fabricated surface composites. Macro/microstructure, microhardness, and wear test analysis were done on these samples, and the results were compared with the base material AA5052-H32. The microstructure analysis showed that the distribution of reinforcement particles in the aluminum matrix is made more uniform by adding hard SiC with graphene nanoparticles, which can reduce the occurrence of particle clustering and agglomeration. As a result, the smallest grain size of 11.2 µm and the highest microhardness obtained was 84.1 HV obtained in hybrid surface composites. Consequently, the hybrid surface composites obtained more improved wear properties than mono surface composites. Thus, the hybrid surface composites achieved the lowest average friction coefficient of 0.304. [ABSTRACT FROM AUTHOR]

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]

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 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]

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.

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]

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]

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]

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 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]

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]

Friction stir processing (FSP) manufacturing technology was used to fabricate medium Mn advanced high-strength steel in this study. The mechanical properties and microstructure of the steel fabricated using FSP were investigated. The steel obtained a total elongation of 35.1% and a tensile strength of 1034.6 MPa, which is about 59% higher than that of the steel without FSP. After FSP, a gradient structure occurs along the thickness direction. Specifically, across the thickness direction from the base material zone to the transition zone and finally to the stirring zone, both the grain size and austenite fraction decrease while the dislocation density increases, which results from the simultaneous effect of severe plastic deformation and recrystallization during FSP. Due to the gradient structure, an obvious difference in the strain across the thickness direction of the steel occurs during the deformation process, resulting in significant hetero-deformation-induced (HDI) strengthening. The deformation mechanism analysis reveals that HDI strengthening and dislocation strengthening are the main factors in the improvement in the strength–ductility balance. The obtained knowledge sheds light on the process of fabricating medium Mn steels with excellent properties using FSP manufacturing technology. [ABSTRACT FROM AUTHOR]

As an industrially reliable, controllable and effective deformation technique, friction stir process (FSP) can significantly refine the grain size, effectively activate prismatic plane and pyramidal plane slip systems of wrought magnesium alloys through intense plastic deformation and grain refinement, improving the mechanical properties and plasticity simultaneously. Therefore, more and more researchers are devoted to revealing the relationship between grain size, morphology and distribution of precipitated phases, and texture modification with the mechanical properties of magnesium alloys after FSP by means of some characterization techniques, such as electron backscattering diffraction, scanning electron microscopy and transmission electron microscopy. In this paper, the research results of FSP in wrought magnesium alloys in the last five years are reviewed. The fundamental principle and advantages of the FSP process are introduced, and the effects of the FSP process parameters and tool size on the microstructure characteristics, textile evolution, dynamic recrystallization mechanism and mechanical properties of Mg–Al–Zn, Mg–Li and Mg–Zn–Zr wrought magnesium alloys are analyzed emphatically. The preparation of ultrafine crystalline microstructures and achievement of superplastic behavior by modification of FSP are discussed in classification. In addition, the current status of metal additive manufacturing processes based on stirred friction processing (such as friction stir additive manufacturing and additive friction stir deposition) in wrought magnesium alloys is discussed in detail. Finally, the future research development and application of FSP in wrought magnesium alloys are prospected. Some reasonable suggestions are put forward to address the existing problems at this stage, which can provide references for further research in the future. [ABSTRACT FROM AUTHOR]

Multi-response optimization of composites was performed using the Taguchi-based desirability approach. Parameters, namely tool rotation speed (900 rpm, 1120 rpm, and 1400 rpm), feed rate (20 mm/min, 40 mm/min, and 60 mm/min), graphene nanoplates (GNPs) content (6.5 vol.%GNPs, 11 vol.%GNPs, and 17.4 vol.%GNPs) each at three levels were considered to optimize and enhance tensile strength and hardness using Taguchi's L9 orthogonal array. Besides Taguchi's analysis and the developed regression model, the artificial neural network was used to validate the results. A confirmation test was compared with the predicted value of composite desirability ( d G ), and a comparison was drawn between experimental and predicted values. From ANOVA, results inferred that vol.%GNPs significantly impacts d G . The obtained tensile strength and hardness values effectively reflect the macrostructural, microstructural studies and XRD results. Fracture analysis of the confirmation sample showed no dimples but continuous deep ridges with sharp, torn edges indicating brittle failure. [ABSTRACT FROM AUTHOR]

In this paper, the effect of ultrasound on the microhardness and microstructure of friction stir welding joints is investigated. It has been found that the area with minimum microhardness is located in the thermomechanically affected zone on the retreating side. An ultrasonic impact resulted in an increase in the size of this area. The weakening of the region is attributed primarily to the low content of hardening particles due to overaging. It was also found that the ultrasonic impact during welding resulted in a 5 times reduction of residual stresses. [ABSTRACT FROM AUTHOR]

Friction stir processing (FSP) is the most effective severe plastic deformation process for creating materials with very fine grains and good properties. The target of the present research is to investigate the influence of FSP on the microstructure and mechanical properties of homogenized 2024 aluminum alloy with and without rare-earth (RE) and thermomechanically treated conditions (TMT). The rare-earth elements used were Ce and La in the form of a master alloy containing (50% Ce + 50% La). The casting of 2024 aluminum alloys, both with and without (Ce + La), was carried out using the conventional stir cast technique. Part of the obtained alloys was homogenized, whereas the other part was thermomechanically treated (TMT). The homogenized 2024 material was exposed to FSP with multiple passes (one, two, and three) to obtain the suitable pass number. After that, the best pass number was performed on the 2024 aluminum alloy refined with RE (Ce + La) and TMT materials. The microstructures in different conditions (homogenized and stir friction) were examined by optical and scan microscopes attached with EDS and Map analyzer. At the same time, a tensile test was conducted to assess the mechanical properties. The findings indicated that the microstructures were significantly refined after adding RE (Ce + La) or applying the TMT technique. Whereas, the microstructures were greatly improved after applying FSP to both conditions. Ultra-fine grains were observed for both TMT and RE-containing alloys after FSP. On the other hand, the results of mechanical properties were significantly increased after applying multiple passes of FSP. The optimum results were obtained when two passes of stir friction were applied to the TMT alloy condition. [ABSTRACT FROM AUTHOR]

Friction stir processing (FSP) stands as an effective approach designed for grain refinement and site-specific microstructural modification. The evolving microstructure during FSP is determined by various variables out of which rate of sample cooling is the key parameter. More often, FSP is conducted in naturally flowing air; however, a large number of studies are conducted by researchers across the world; stressing the importance of additional sample cooling strategy for tailoring the material microstructure. Such strategies vary not only in terms of the cooling medium used but also with regard to various other compliant conditions that must be fulfilled for the cooling process to make them successful and economically viable. This work critically reviews the most prevalent methods practiced by various researchers and industries for controlled sample cooling during and after FSP. The underlying mechanisms; advantages; disadvantages; and limitations of each procedure along with the resulting microstructure and material performances are discussed and recommendations are provided [ABSTRACT FROM AUTHOR]

It is difficult to prepare large-area bulk ultrafine-grained (UFGed) titanium alloys with uniform structure via multi-pass overlapping friction stir processing (MP-FSP) due to the low thermal conductivity and poor flow deformation ability of titanium alloys. Here, we proposed a new layer-by-layer MP-FSP method to control the defect and microstructure of the Ti–6Al–4V alloy. As a result, the as-cast coarse microstructure was changed directly to the defect-free large-area bulk UFG microstructure. The bulk UFG exhibited a uniform microstructure with average grain sizes of 0.7–0.82 μm and over 90% of high angle grain boundaries. Moreover, the bulk UFG titanium alloy exhibited high hardness (357 HV) and great ultimate tensile strength (1177 MPa), which were much higher than those (308 HV and 739 MPa) of the base material. In addition, the bulk UFG had good thermal stability at a high temperature of 700 °C. Different from the bulk MP-FSP UFGed aluminium alloys where there is generally abnormal grain growth (AGG) at high temperatures, there was no AGG phenomenon in bulk MP-FSP UFGed titanium alloys even at 900 °C. This study provides an effective short-process method for preparing large-area bulk UFG titanium alloys with uniform structure and good thermal stability.

Modified layers with refined and homogenized microstructure were obtained on a cast manganese aluminum bronze (MAB) by friction stir processing (FSP) and laser surface melting (LSM). In 3.5% NaCl solution, a much more protective film was formed and uniform corrosion occurred for the two surface-modified MABs. The corrosion rate of the cast sample was reduced by a factor of 29.73% after FSP and 51.35% after LSM. The cavitation erosion (CE) rate of the cast MAB was about 1.83 and 3.07 times larger than that of the FSP and LSM samples, respectively. The CE resistance increment was highly attributed to the improved hardness and enhanced nano-indentation behavior after FSP or LSM. For each MAB, the CE resistance decreased with extended pre-immersion time. Compared with the result of the correspondingly freshly-prepared sample, the CE rate was raised by a factor of 36.22%, 42.97% and 44.00% after 30 days’ pre-immersion for the cast, FSP and LSM MABs, respectively. For the cast and FSP MABs, mechanical impact was the leading factor accounting for CE degradation. For the pre-corroded samples, corrosion damage at the β and κ phases weakened the mechanical properties and thus triggered more grievous material exfoliation under CE. For the LSM MAB, CE-corrosion synergy dominantly gave rise to the CE damage. Corrosion at grain boundaries after pre-immersion also deteriorated the CE performance. The LSM MAB possessed the highest corrosion and CE resistances because the fine single-phase microstructure reduced the galvanic corrosion effect and crack propagation tendency under CE impact.

Friction stir welding of 7075 aluminum alloy plate with a thickness of 10 mm was carried out with a self-designed stirring tool, and after welding, an irregular transitional zone between the tool shoulder zone and the nugget zone, known as the turbulent zone, was discovered on the advancing side of the weld. The formation mechanism of the turbulent zone was analyzed by observing the transverse and longitudinal sections of the joint cross section. The grain size, the degree of dynamic recrystallization, the misorientation angle distribution in the turbulent region were evaluated by electron backscatter diffraction (EBSD). The grain size in the turbulent zone is large with an average grain size of 2.98 μm. The proportion of substructure is as high as 75.1 %, which makes the hardness value higher than that of other areas of the weld. In addition, layered tensile mechanical test results show that the tensile strength of the turbulent zone layer (342 MPa) is comparable to that of the central layer of the weld nugget zone (345 MPa). [ABSTRACT FROM AUTHOR]

In this work, the effect of SiC and Al2O3 nanoparticles and multipass friction stir processing (MPFSP) on the metallurgical properties of AZ91D was carefully investigated and observed a homogenous dispersion of nanoparticles and refined grain size in the processed zone. The presence of the Mg17Al12 intermetallic compound in the MPFSP of AZ91D with SiC and Al2O3 nanoparticles has significant implications for the material's properties. Mg17Al12 is a typical intermetallic phase formed in magnesium alloys and can profoundly affect thermal, microstructural, and mechanical properties. The intermetallic phase can improve the processed region's strength due to its inherent hardness and solid solution strengthening effect, resulting in enhanced tensile properties and hardness. As the FSP passes increased, the tendency for reinforcement agglomeration diminished. Before undergoing MPFSP/(SiC + Al2O3), the base metal AZ91D exhibited an ultimate tensile strength (UTS) of 208.36 MPa and a strain percentage 15.72. After implementing MPFSP/(SiC and Al2O3) on AZ91D, the UTS consistently increased with each FSP pass. This effect was evident at the fourth FSP pass, yielding a higher UTS of 284.35 MPa. In essence, this process facilitated a marked enhancement in the metallurgical properties of AZ91D, signifying the efficacy of the MPFSP approach when combined with reinforcement particles. The hardness value was higher when the indenter engaged with Mg17Al12 than α-Mg. The SZ of 4-pass FSP (Al2O3+SiC)/AZ91D reached a maximum hardness value of 69.37 HV, while single-pass FSP (Al2O3)/AZ91D exhibited a minimum value of 64.89 HV. [ABSTRACT FROM AUTHOR]

Friction stir processing (FSP) is considered as a prolific secondary processing method to enhance the properties of aluminium matrix composites (AMCs) by altering their microstructure. AA6061/(15 wt.%) Al3Zr and AA6061/(15 wt.%) Al3Ni AMCs were manufactured with the addition of zirconium (Zr) and nickel (Ni) powders to the molten AA6061 and followed by FSP. The change in microstructure of AMCs before and after FSP was analysed through optical and electron microscopies integrated with electron back-scattered diffraction. The cast AMCs exhibited clustered, sharp cornered particles with micropores near the particle–matrix interfaces and showed coarse-grained microstructure. Upon conducting FSP, the particle distribution was uniform along with the elimination of cast defects. The sharp cornered particles were fragmented into finely dispersed particles in the aluminium matrix. Significant grain refinement was observed on AMCs owing to the pinning effect of particles and severe deformation happened during FSP. FSP enhanced the accumulation of dislocations and resulted in modification microstructure, which favoured attaining a combination of ductility and tensile strength. The strength attained by the Al3Ni AMC was higher than that of Al3Zr AMC due to the existence of finely dispersed near round-shaped particles, which exhibited better load-bearing ability. [ABSTRACT FROM AUTHOR]

In this study, we have employed friction stir processing to strategically modify the microstructure of AA-Mg alloys, resulting in a direct enhancement of their mechanical properties. The experiments encompassed a range of tool speeds ranging from 800 to 1600 rpm and feed rates ranging from 20 to 80 mm/min. Employing a single-pass approach across all combinations, samples were extracted from the stir zone region to evaluate hardness and wear characteristics. The evaluation involved Vickers hardness tests to quantify hardness and pin-on-disc tests to examine the tribological attributes of the specimens. The worn-out surfaces of the specimens were examined using scanning electron microscope imagery. There is a substantial increase in hardness when compared with the base material, i.e., 78 HVN is up to 96 HVN for 20 mm/min at 1200 rpm, 98 HVN for 20 mm/min at 800 rpm, 106 HVN for 60 mm/min at 1600 rpm and 96 HVN for 80 mm/min at 1600 rpm. Furthermore, the coefficient of friction increased from 0.341 for base materials to a maximum of 0.635, 0.667, 0.604, and 0.646 for the same combination of speed and feed rate, respectively. The maximum change in percentage is 26% in hardness and 49% in wear coefficient. [ABSTRACT FROM AUTHOR]

This study investigates the microstructural and mechanical behavior of Al6061-TiC-Graphite hybrid metal matrix composites fabricated by the ultrasonically stir casting process. The effects of TiC and graphite on the phase, microstructure, hardness, and tensile strength of the composites are evaluated. Scanning electron microscopy, Energy dispersive spectroscopy, and X-ray diffraction analysis techniques were used to investigate the microstructure and phase composition of the composites. The results show that the addition of TiC and graphite improves the microstructure and mechanical properties of the composites. The maximum hardness and tensile strength were obtained for the composite with 2 wt.% TiC and 1 wt.% graphite. The study provides insight into the development of advanced metal matrix composites with improved mechanical properties for potential use in various industrial applications. [ABSTRACT FROM AUTHOR]

The purpose of this study is to find the influence of volumetric percentage of High Entropy Alloys (HEA) on Mechanical Behaviour of 6061 T6 Al alloy surface composite processed by Friction Stir Processing (FSP). Al-6061-T6 alloy was considered as the base material and Al-Fe-Cu-Ni-Zn as HEA with relevant weight proportion. HEA were reinforced on plate by making a slot on them using shaper and varying the volumetric percentage of slot. Friction stir processing was carried out on the samples with optimal working parameters. Study of the properties such as microstructure of joint and strength will directly affect the parameters such as corrosion of joint which will decide the service and life of the joint in different environments. Radiography was carried out for the samples after FSP to check for any defects or cracks. The microstructures for all the samples are studied based on grain size refinement and uniform Distribution of HEA around the travel pattern of tool. It is observed that micro hardness of samples increased with increase in percentage of HEA which is more than the hardness value of base material (Al alloy). It is evident that 4% sample exhibits better tensile properties than other. [ABSTRACT FROM AUTHOR]

Fe–Mn–Cr–N austenitic stainless steel is widely used in engineering fields because of its good ductility, but its relatively low yield strength limits its application range. In this study, Fe–Mn–Cr–N steel was fabricated with different parameters by friction stir processing (FSP). To explain the effect of the rotation rate and feed speed on the microstructure evolution and mechanical properties of Fe–Mn–Cr–N steel, four sets of parameters were selected. The numerical simulation results reveal that the maximum temperature and strain at the tool-workpiece interface on the advancing side (AS) are 948.8 °C and 39.3 mm/mm, respectively. Under the action of severe strain and frictional heat production during processing, the original coarse columnar grains were refined into uniform equiaxed grains with an average grain size of approximately 10 μm in the stir zone (SZ). Moreover, under the experimental conditions, the δ-ferrites gradually transformed into austenite, and all the δ-ferrites disappeared in the SZ with the greatest strain. In addition, a large number of Σ3 twins formed in this region. Consequently, microstructure refinement is dominated by dynamic recrystallization (DRX), while nucleation is accelerated by dissolution and spheroidization of δ ferrites and evolution of Σ3 twin boundaries. The Fe–Mn–Cr–N steel fabricated at 600 rpm-50 mm/min had the best comprehensive mechanical properties, i.e., its YS, UTS and El changed to 400.9, 649.0 MPa and 60.7 pct from 211.4, 421.2 MPa and 62.4 pct of the original as-casted Fe–Mn–Cr–N steel, respectively. The improvement in the YS was mainly attributed to solution strengthening (σSS = 114.4 MPa) and boundary strengthening (σGB = 189.5–238.1 MPa). [ABSTRACT FROM AUTHOR]

The present investigation delves into the friction stir welding of AA5052 and AZ31B alloys, examining the effects of three distinct parameter configurations. A face-centered central composite design, structured to incorporate full replications for comprehensive and reliable analysis, was employed. A pivotal element of this study is implementing an advanced deep neural network (DNN) model. Characterized by its varied activation functions, structural parameters, and training algorithms, this DNN model was adeptly configured to precisely predict the tensile strength and microhardness of the welded joints. This comprehensive examination also included a quantitative assessment of the parameter effects on joint microstructure and mechanical properties. Flawless welds with exemplary surface characteristics were attained through a meticulously optimized set of parameters: a tool rotation speed set at 825 rpm, a tool traverse speed of 15 mm/min, and a shoulder diameter of 18 mm. During the welding process, the formation of intermetallic compounds, specifically Al12Mg17 and Al3Mg2, was observed. An exceptionally refined grain size of 2.23 µm was observed in the stir zone, contributing to the joint's enhanced tensile strength, measured at 180 MPa. The hardness of the specimen fabricated at the high rotational speed is more elevated due to the brittle intermetallic compounds. The better mechanical properties are related to the reduction and distribution of intermetallic compounds formed in the interface zone. [ABSTRACT FROM AUTHOR]

The motive of present work is to explore the variation in the material characteristics of steel upon multi-pass friction stir processing. Steel plates (IS2062) that were 3 mm thick, were subjected to friction stir processing in a multi-pass manner. The selected transverse speed was 150 mm/min, along with a tool rotation of 800 RPM when using a tungsten carbide tool (shoulder diameter—10 mm). Steel plates were processed using the single-pass, double-pass, and triple-pass travel of the rotating tool to observe the impact of multi-pass processing on the properties of steel plates. Multi-pass friction stir processing resulted in a higher micro-hardness of 175 VHN after the second pass, in comparison to the unprocessed metal, which had a micro-hardness of 130 VHN, owing to the collective effect of the plastic flow of the material due to the rotation of the tool and frictional heat, which also leads to grain refinement. The second pass evidenced an average grain size of 22 microns, whereas the unprocessed material had an average grain size of 57 microns. The results of EBSD and SEM characterization showed reasonably improved material properties of the processed work materials. [ABSTRACT FROM AUTHOR]

Friction stir processing (FSP), a severe plastic deformation process, was applied on commercially pure Ti to obtain an improved microstructure. The process yielded a refined microstructure and higher mechanical properties at room temperature (RT). Yet the microstructure was found to contain bright bands demonstrating high hardness values of about 500 HV. High-resolution scanning electron microscopy (HRSEM) as well as electron backscattering diffraction (EBSD) analysis indicated that these bands were composed of extra-fine equiaxed α-Ti grains with an average radius of 1–2 microns. In addition, a retained β phase was detected at the boundaries of these α-Ti grains, together with a small quantity of separate β grains. The results of a fractography study conducted on broken tensile specimens showed that the material that underwent FSP was free of defects and that the fracture started at these bands. It is proposed that these bright bands are due to excessive deformation occurring during the processing stage, leading to an accelerated dynamic recrystallization (DRX) process. In turn, these heavy deformation regions act as a strengthening constituent, making the material superior to the parent material as far as its mechanical RT properties are concerned. Consequently, this means that the FSP of CP-Ti has the potential to serve as an industrial means of improving the mechanical properties of the material. [ABSTRACT FROM AUTHOR]

Friction stir processing (FSP) is a solid-state treating method to enhance the mechanical properties of materials by altering their microstructure. In this study, FSP was applied to the AZ91 magnesium alloy cladding layer prepared using cold metal transition (CMT) technology, and the purpose was to investigate the effect of the traverse speed of the H13 steel stirring head under a constant rotation speed on the microstructure and mechanical properties of the cladding layer. The results demonstrated that FSP could effectively decrease the grain size of the cladding layer and lead to the dispersion and dissolution of the coarse β-Mg17Al12 second phase into the α-Mg matrix. The mechanical characteristics of the processed cladding layer were significantly enhanced compared to the unprocessed cladding layer due to the grain refinement and second-phase strengthening induced by FSP. When the stirring head rotation speed was set at 300 r/min, the average microhardness and tensile properties of the specimens showed a tendency of initially increasing and then dropping as the traverse speed increased. The cladding layer, obtained at a traverse speed of 60 mm/min, displayed optimal mechanical properties with an average microhardness, tensile strength, and elongation of 85.6 HV0.1, 278.5 MPa, and 13.4%, respectively. [ABSTRACT FROM AUTHOR]

Low-cost hybrid-reinforced magnesium metal matrix composite (HMMC) materials present a revolutionary category of materials achieved by combining two or more distinct reinforcing elements within the magnesium (Mg) matrix. The main focus of this research is to fabricate Mg-based HMMCs with exceptional mechanical and other characteristics by utilizing Mg substrate AZ61A as the base material. To achieve this, nano-titanium carbide (TiC), nano-silicon carbide (SiC), and fly ash (FA) were selected as hybrid reinforcements, and the friction stir processing technique was employed for their incorporation. The microstructural, thermal, mechanical, wear, and fracture properties of synthesized HMMCs were carefully examined using a conventional testing approach. The findings demonstrate that the grain size of the base AZ61A alloy was measured at 32 µm, whereas the AZ61A/FA/TiC/SiC composite exhibited a remarkable reduction to 3.5 µm. Notably, this reduction in grain size leads to simultaneous enhancement in mechanical properties. The microhardness, ultimate tensile strength, and ultimate compressive strength of the developed HMMC showed an impressive increase, measuring 2.09 times, 2.75 times, and 2.10 times higher, respectively, compared to their initial values of the base material. Moreover, a significant enhancement in wear resistance was also observed, attributed to the increased hardness and homogenous hybrid reinforcement dispersion into the HMMCs. In addition, it was evident that the synergistic combination of different reinforcement particulates in Mg-based alloy improves overall fracture resistance and catastrophic failure and mitigates crack propagation. [ABSTRACT FROM AUTHOR]

Experimental laboratory equipment for friction stir welding (FSW) as a result of working out the optimal welding modes at different linear velocities allows producing high-quality butt joints from thin ductile metals. With the development of new mathematical methods for modeling thermodeformational processes, it became possible to analyze the stress-strain state and thermomechanical processes occurring in the FSW joint zone, which is necessary for predicting the operational properties, strength and service life of welded structures made of thin metal. Using mathematical models and finite element analysis, the temperature distributions from the volume heat source at FSW were visualized, and the residual deformations and stresses in the zone of butt-welded joints of thin sheets of magnesium alloys were numerically determined. In the future, it is advisable to determine the effective balance of the linear speed and the rotation speed of the FSW tool to obtain better homogeneity of the weld structure and reduce heat input into the metal during welding. [ABSTRACT FROM AUTHOR]

The article presents an assessment of the possibility of using ashes from the combustion of coal and biomass as a reinforcing phase in metal matrix composites. The composite surface layer was produced by means of the FSP (friction stir processing) method, using an original hole solution with a shifted working zone of the pin. The composite matrix was AA7075 alloy. The obtained composite was subjected to microscopic observations, tribological tests, and hardness measurements. The microscopic examinations revealed favorable changes in the microstructure, in particular, strong refinement of the grains, uniform distribution of the reinforcing phase, and good bonding of the particles of this phase with the matrix material. Changes in the microstructure resulted in a significant increase in the hardness (from 36 to 41% depending on the type of reinforcing phase) and wear resistance (from 24.1 to 32.9%), despite partial dissolution of the intermetallic phases. It was found that the effect of strengthening the matrix and the uniformity of the distribution of the reinforcing phase depend on the physicochemical properties of the used powders, especially on the shape and size of the particles. The research shows that the use of ashes as a reinforcing phase in composites is fully justified. [ABSTRACT FROM AUTHOR]

2A12 hot-rolled aluminum alloy has high plasticity and toughness, and is widely used in the manufacturing of structural parts in aviation, aerospace, automobiles, and other fields. To explore the effect of friction stir welding process parameters on the welded joint properties of 2A12 hot-rolled aluminum alloy, experimental investigations were conducted. The surface appearance of the welded joints under different process parameters was observed, the microstructure, microhardness, tensile strength, yield strength, elongation and the fracture morphology of the welded joints were assessed. The findings suggested that when the rotation speed was 600 rpm and the forward speed was 250 mm/min, the tensile strength, yield strength and elongation of the welded joint were all maximum, which were 437.6 MPa, 381.6 MPa and 7.5 % respectively, reaching 85.5 %, 88.1 % and 35.7 % of the base material. Under the same forward speed, the tensile strength and elongation of the welded joint initially rose and subsequently declined with the increment of rotation speed. The microhardness distribution of the welded joint exhibited a W-shape pattern. The fracture morphology showed that the fracture type of the welded joint was a ductile fracture. Unlike the base material, the welded joints did not exhibit significant necking during the tensile testing. The research results can be utilized as a reference for the engineering application of friction stir welding of 2A12 hot-rolled aluminum alloy. [ABSTRACT FROM AUTHOR]

In this paper, the microstructure, mechanical properties, and corrosion behavior of friction stir welded (FSW) joints of the two aluminum alloys 6005A‐5083 were investigated and their correlation was discussed. In contrast to FSW joints of the same aluminum material, this results in a "V" shape curve of hardness distributed nonsymmetrically along the weld. The lowest hardness area occurs at the interface between the heat‐affected zone and the thermo‐mechanically affected zone of 6005A (6‐HAZ and 6‐TMAZ) due to the transformation of the β" phase under the influence of heat input during the stir friction process. This also leads to all tensile specimens fracturing in this area. The corrosion behavior of the FSW joint in acidic solution containing Cl− was determined by an exfoliation corrosion (EXCO) test, an intergranular corrosion (IGC) test, and potentiodynamic polarization measurements, based on the potential application in acid rain environment. The results showed that the corrosion resistance order in the acidic solution is: 6‐HAZ > NZ > 6‐BM > 5‐HAZ > 5‐BM. The 5‐BM has the worst corrosion resistance due to the high corrosion sensitivity of Al3Mg2 in acidic solution. However, good corrosion resistances are shown in NZ and 6‐HAZ, which is related to a relatively homogeneous microstructure in NZ and a dissolution or coarsening of β" phases in 6‐HAZ because of frictional heat input. [ABSTRACT FROM AUTHOR]

Metal inert gas (MIG) welding is widely employed for aluminum alloy welding, but high residual stress, coarse grain's structure, porosity, and micro-cracks occur during MIG welding. To avoid these defects, friction stir processing (FSP) was employed to the MIG welded joints of AA7075 and AA6082 with ER4043 filler. The grain structure of the weld fusion zone (WFZ) was categorized by eutectic precipitated Mg2Si, and primary α-Al. The elongated, coarse grain structure of the MIG weldment decreased after a one pass FSP. The Mg2Si precipitates were disseminated due to the enhancement of dispersion and dissimilar metal fraternization. The fraction area of the refined grains increases when the FSP pass increases. Furthermore, the effective enhancement of the joint efficiency was observed in the MIG + 4Pass FSP due to the grain refinement. The ultimate tensile strength (UTS) of 169.73 MPa of the MIG welded joint was observed with a grain size of 17.9 ± 0.3, while the highest UTS of 223.84 MPa was perceived at 4 passes of MIG + FSP joints with an elongation of 12.45%. The grain structure was also refined as the FSP pass increased, and the minimum grain size (2.6 ± 0.3 µm) was perceived at MIG + 4Pass FSP. Multipass FSP leads to refinement and homogenization of the microstructure, increasing the microhardness of the weldment. The average hardness value of the MIG weldments at the WFZ was 84 HV, while the microhardness of MIG + FSP joints of 1Pass, 2Pass, 3Pass, and 4Pass FSP was 88, 96, 101, and 110 HV at the stir zone (SZ). [ABSTRACT FROM AUTHOR]

Manufacturing for next-generation thermal management is very important for electrical and electronics industries to meet sustainable development goals through electrification. In this study, thermal management manufacturing application and analysis of channel formation characteristics for copper and aluminum materials are investigated using different tool designs consisting of three probe thread pitches and four process pitches of the Friction Stir Channeling (FSC) process. Channel characteristics such as shape, area, perimeter, and closing angle are investigated. Analysis of microstructure around the channel using optical microscopy and electron beam scattered diffraction, Vickers hardness measurements at channel cross-section, surface features, and roughness inside channels are conducted. Eventually, the FSCed channels are evaluated for thermal efficiency performance. Complex materials flow with the combined effect of materials extraction and forging through stirring followed by shearing action is revealed as the channel formation mechanism in FSC. The higher thread pitch on the tool probe resulted in non-uniform material flow during channel formation and eventually formed non-rectangular channels. At the interface of the ceiling zone-unprocessed region in copper, intriguing features of piling up grain boundaries, low angle grain boundaries, and higher kernel average misorientation are observed. Unique surface roughness textures are noticed for four different walls of channels in copper and aluminum. The aluminum channel's root mean square roughness (R q) value is 63.4% rougher on the retreating side and 246% rougher on the ceiling side compared to the copper channel at the same location. The channel produced by the 1.5 mm thread pitch tool was found to be the most efficient in terms of cooling power for both copper and aluminum materials. For Channels fabricated by thread pitches of 1.0 mm, 1.5 mm, and 2.0 mm in copper were found to be 62.4%, 67.3%, and 82.9% more efficient than aluminum channels. [Display omitted] • First investigation on obtaining channels in copper using friction stir channeling (FSC). • In-depth investigation on channel formation characteristics for copper as well as aluminum materials. • Correlation on probe's thread pitch and channel formation characteristics is established. • Distinguishable microstructural variations at interface between channel ceiling zone and base material are revealed. • The cooling power capacity of copper channel is 62% to 83% higher as compared to aluminum for different thread pitches. [ABSTRACT FROM AUTHOR]

• The microstructure of Mg-Al-Sn-RE anode is tailored via friction stir processing. • The processed anode has fine grains, low dislocation density, and weak orientation. • This unique anode structure boosts the voltages and capacities of Mg-air battery. • The discharge mechanism corresponding to the unique anode structure is analysed. Constructing the magnesium alloy with fine grains, low density of dislocations, and weak crystal orientation is of crucial importance to enhance its comprehensive performance as the anode for Mg-air battery. However, this unique microstructure can hardly be achieved with conventional plastic deformation such as rolling or extrusion. Herein, we tailor the microstructure of Mg-Al-Sn-RE alloy by using the friction stir processing, which obviously refines the grains without increasing dislocation density or strengthening crystal orientation. The Mg-air battery with the processed Mg-Al-Sn-RE alloy as the anode exhibits higher discharge voltages and capacities than that employing the untreated anode. Furthermore, the impact of friction stir processing on the electrochemical discharge behaviour of Mg-Al-Sn-RE anode and the corresponding mechanism are also analysed according to microstructure characterization and electrochemical response. [ABSTRACT FROM AUTHOR]

This study investigates the temperature distribution behavior during friction stir Processing (FSP) of AA6061-T6 plates with varying SiC particle volume fractions (Vf). FSP have been conducted under consistent parameters: a tool rotational speed of 1100 rpm, tool traverse speed of 1.5 mm/s, and tool tilt angle of 2°. Temperature was monitored using K-type thermocouples inserted into the plates, providing a temperature distribution profile for variation in SiCp. Scanning electron microscopy and optical imaging was employed for surface morphology analysis. Mechanical properties such as ultimate tensile strength, yield stress, % elongation, microhardness, and fractography were examined. The findings revealed a continuous increase in temperature with Vf, peaking at 0.25% Vf (353.45 °C) and then decreasing at 0.3% Vf (295.66 °C). Microstructure analysis showed uniform SiCp distribution at 0.25% Vf. Similar trends were observed for ultimate tensile strength, yield strength, and microhardness, with maximum values of 341 MPa, 233 MPa, and 127 HV0.1, respectively, at 0.25% Vf. % elongation decreased with increasing Vf. These results contribute to the understanding of how SiCp reinforcement affects the FSW process and the resultant material properties. [ABSTRACT FROM AUTHOR]

Enhancing the mechanical properties of conventional ceramic particles-reinforced aluminum (Al 1060) metal matrix composites (AMCs) with lower detrimental phases is difficult. In this research work, AMCs are reinforced with graphene nanosheet (GNS) and hybrid reinforcement (GNS combined with 20% SiC, synthesized by shift-speed ball milling (SSBM), and further fabricated by two-pass friction stir processing (FSP). The effect of GNS content and the addition of SiC on the microstructure and mechanical properties of AMCs are studied. The microstructure, elemental, and phase composition of the developed composite are examined using SEM, EDS, and XRD techniques, respectively. Mechanical properties such as hardness, wear, and tensile strength are analyzed. The experimental results show that the GNS and the SiC are fairly distributed in the Al matrix via SSBM, which is beneficial for the mechanical properties of the composites. The maximum tensile strength of the composites is approximately 171.3 MPa in AMCs reinforced by hybrid reinforcements. The tensile strength of the GNS/Al composites increases when the GNS content increases from 0 to 1%, but then reduces with the further increase in GNS content. The hardness increases by 2.3%, 24.9%, 28.9%, and 41.8% when the Al 1060 is reinforced with 0.5, 1, 2% GNS, and a hybrid of SiC and GNS, respectively. The SiC provides further enhancement of the hardness of AMCs reinforced by GNS. The coefficient of friction decreases by about 7%, 13%, and 17% with the reinforcement of 0.5, 1, and 2% GNS, respectively. Hybrid reinforcement has the lowest friction coefficient (0.41). The decreasing friction coefficient contributes to the self-lubrication of GNSs, the reduction in the contact area with the substrate, and the load-bearing ability of ceramic particles. According to this study, the strengthening mechanisms of the composites may be due to thermal mismatch, grain refinement, and Orowan looping. In summary, such hybrid reinforcements effectively improve the mechanical and tribological properties of the composites. [ABSTRACT FROM AUTHOR]

Magnesium alloy-based matrix composites are extensively used in transportation industries because of their high specific strength and low weight. Several existing technologies were utilized for preparing these composites in any proportion of constituent elements. However, friction stir processing (FSP), which employs plastic deformation with high-energy input, has proven as the most successful with proper homogenization. This study examines the microstructure and mechanical characteristics evolved by FSP of a novel magnesium alloy grade (AZ31) with Titanium dioxide (TiO2), Multi-walled carbon nanotubes (MWCNT) and Research grade Graphene nanoplatelets (GNP) that have considerable electrical, thermal and mechanical performance. At a parametric combination, tool rotation of 1200 rpm, traverse speed of 80 mm per minute, plunge depth with 0.25 mm, AZ31 alloy was processed on a specifically engineered fixture with subzero coolant circulation through it. The average size of grains of the base alloy reduced from 52.96 µm to 2.07 µm (AZ31/TiO2), 3.19 µm (AZ31/MWCNT) and 2.54 µm (AZ31/GNP) composites at this combination. The hardness and tensile strength were enhanced from 115 to 130% and 25 to 38%, respectively. Micrographs shows that the shortened grain elongation occurred due to coolant circulation resulted in restricted strengthening precipitate dissolution, which usually occur at high temperature. [ABSTRACT FROM AUTHOR]

The present study investigated the effect of tool rotational speed on the microstructure and mechanical behavior of friction stir processed AA 7050 aluminum alloy using an optical micrograph, scanning electron microscope, tensile test, impact strength, and Vickers microhardness. The alloy was processed at 40 mm min−1 as a travel speed combined with three tool rotational speeds, 800, 1200, and 1600 rpm. The visual inspection of the surfaces of the samples revealed that the alloy could be successfully friction stir processed at any rotational speed. The results indicated that the mean grain size of the stir zone decreases with increasing the tool rotational speed (from 45 to 9 µm). The development of the precipitates θ, (η and η), (T and T), and S phases was significantly controlled by the tool rotational speed. Consequently, the microhardness, tensile strength, and impact strength of the AA7050 alloy were enhanced by friction stir processing due to the combination of grain refinement and precipitation strengthening. The optimum mechanical properties were obtained for the sample processed with a tool rotational speed of 1600 rpm. [ABSTRACT FROM AUTHOR]

Medium- and high-entropy alloys (MEAs/HEAs) or multi-principal element alloys are a new class of promising alloys with wide application possibilities in several industries like nuclear, offshore, liquefied natural gas, and transportation, among others. The development of these revolutionary alloys comes with the need to separately unravel their weldability as the microstructure and the welding-induced thermal responses of the single, dual, and multi-phase HEAs differ. Detailed knowledge of the weldability of MEAs/HEAs is still at the early stage and remains a useful link between the developed MEAs/HEAs and their full-scale industrial manufacturing applications. The intense heat input of fusion welding techniques easily introduces different or combined challenges such as elemental segregation, inhomogeneous phase transformation, solidification cracking, and coarsened structure to the weld metals of HEAs. As a result, this paper provides a state-of-the-art review of the low heat-input or solid-state welding and friction stir processing of MEAs/HEAs. The welding section covers explosive and friction stir welding processes of HEAs. Insights into the future research areas that can further progress the scientific understanding and weldability of MEAs/HEAs are briefly explicated in this paper. [ABSTRACT FROM AUTHOR]

Friction stir processing (FSP) is a solid-state processing technique used to refine the microstructures of metallic alloys. It involves inserting a rotating tool into the material, which generates heat and plastic deformation, leading to the recrystallization and refinement of the microstructure. The aluminium alloy 7050 is a high-strength alloy possessing good corrosion resistance, and is commonly used in aerospace applications. By incorporating SiC particles into the alloy with different percentiles of 0 to 1%, the resulting composite can have improved mechanical properties, such as higher strength and stiffness, as well as increased wear resistance. Mechanical testing and optical metallographic characterization were conducted. The test results showed that weldments have improved mechanical properties compared to the base material, making them suitable for high-strength and low-weight applications. [ABSTRACT FROM AUTHOR]