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Friction stir processing (FSP) enables surface modifications can likely be applied as a new post-weld treatment for improving fatigue strength. When applying FSP to high-strength materials, tool wear occurring at the interface between the tool tip and the topmost steel layer has been regarded as an unavoidable issue and is related to the tool rotational speed. The present study investigated the relationship between the tool rotational speed and fatigue strength of arc-welded high-strength low-alloy (HSLA) steel joints with weld toes subjected to FSP using a spherical-tip WC tool. FSP was conducted on the weld toe of HSLA steel joints with various tool rotational speeds. Tool wear increased with increase in tool rotational speed, and consequently contents of constituent elements of the WC tool increased in the topmost steel layer of weld toes, leading to large increase in fatigue strength. One reason for the increase with tool rotational speed is significant increase in solid solution hardening due to supersaturated W and C in the topmost steel layer consisting of martensite laths. The hardened topmost steel layer prevented fatigue crack initiation, and the increased fatigue strength depended on the contents of supersaturated W and C. Alloying of the topmost steel layer with tool constituent elements of W and C accompanied with WC tool wear during FSP is unique additive manufacturing to increase the fatigue strength of welded joints, and can be employed locally on structural components susceptible to fatigue.

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

The relationship between as-cast and post-friction-stir-processed microstructures was assessed by a combination of quantitative metallography and statistical analysis. Two distinct as-cast microstructures, resulting from commercial and continuous casting processes, were subjected to multiple friction stir passes and subsequent metallography by SEM with EDS. X-ray maps were used to elucidate Si particles for quantitative image processing. Progressive homogenization with each successive pass was observed in both alloys. Continuously cast samples exhibited Si particle coarsening, while commercially cast alloys undergo Si particle refinement. Aspect ratio of particles remains constant throughout multiple FSP passes despite changes in spatial and particle size distribution. Trends in distributions of Si particle size and nearest neighbor distances with each pass are presented.

Wire-based friction stir processing is introduced as a solid-state surface alloying strategy for surface alloying of AZ31 magnesium alloy with aluminum, as a key alloying element in magnesium alloys. This technique enables the formation of a defect-free, grain refined and alloyed surface with the increased volume fraction of Mg-Al second phase, and thus, enhanced surface hardness. This simple technique provides a solid-state surface alloying pathway to improve the surface properties of the metallic materials.

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

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

The results obtained by ISIM Timisoara to the development of the friction stir welding process (FSW) have supported the extension of the researches on some derived processes, including friction stir processing (FSP). The experimental programs (the researches) were developed within complex research projects, aspects regarding the principle of the process, modalities and techniques of application, experiments for specific applications, being approached. The paper presents good results obtained by friction stir processing of cast aluminum alloys and copper alloys. The optimal process conditions, optimal characteristics of the processing tools were defined. The complex characterization of the processed areas was done, the advantages of the process applying being presented, especially for the cast aluminum alloys: EN AW 4047, EN AW 5083 and EN AW 7021. The characteristics of the processed areas are compared with those of the base materials. The results obtained are a solid basis for substantiating of some specific industrial applications, especially in the automotive, aeronautical / aerospace fields.

In this work, the effect of friction stir processing (FSP) on tungsten inert gas welding (TIG) has been observed to improve mechanical properties and wear resistance behavior of TIG-welded joint of AA7075 and AA6061. The TIG-welded joints were processed by FSP at various tool rotational speeds of 700, 800, 900, 1000, and 1100 r/min with a constant feed rate of 70 mm/min and tilt angle of 1°. The maximum joint efficiency of 92.81% was observed in TIG + FSP-welded joint with filler ER5356 at a rotational tool speed of 1100 r/min. The maximum tensile strength of 284 MPa was observed in TIG + FSP-welded joint with filler ER5356, whereas the minimum tensile strength of 124 MPa was observed in the TIG weldment with filler ER4043. The cleavage facets, tears ridges, and large dimples were observed in fractured specimens of TIG-welded joints, whereas fine and equiaxed dimples were observed in TIG + FSP-welded joints. The maximum micro-hardness of 137 HV in the stir zone was observed in TIG + FSP-welded joint at a rotational tool speed of 1100 r/min. Due to intense precipitate (MgZn2) kept in the stir zone with filler ER5356, the TIG + FSP-welded joints using filler ER5356 have superior wear resistance compared to TIG and TIG + FSP-welded joint with filler ER4043.

Friction stir processing (FSP), an adaption of the solid-state joining process friction stir welding (FSW), is now a widely recognized severe plastic deformation (SPD) technique. It induces microstructural refinement in the metallic materials which enhances their formability and other mechanical properties. Dynamic recrystallization occurs during the stirring phase which leads to reduction in the grain size and texture modification. Breaking up of the intermetallics and precipitates with their homogeneous distribution in the matrix is also accompanied. This further improves the material's ability to attain maximum ductility during plastic deformation at higher temperatures, resulting in very large uniform elongations (>200%) termed as ‘superplasticity’. Optimization of FSP parameters activates superplastic behaviour in different magnesium alloys at low temperatures and high strain rates. It has become the focal point of the recent researches owing to its huge potential in the light-weight structural applications. In addition to the essential aspects of superplasticity, this article highlights the major explorations in the area of superplasticity of magnesium alloys using FSP method and it's recently developed variants.

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

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

Made available in DSpace on 2021-06-25T10:27:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-01 Petrobras Friction stir welding is a solid-state joining/processing technique that offers high strength and productivity, resulting in a microstructure similar to hot working cycles. However, high melting temperature metals such as steels cause excessive wear over welding tools, representing a significant economic issue. Most studies conducted in steels have used polycrystalline cubic boron nitride (PCBN) and W-Re composite tools, which offer a combination of high strength and hardness at high temperatures, along with high-temperature stability. However, even those tools are susceptible to tool wear. In the present study, experimental data was collected during friction stir processing of X70 grade pipeline steel plates, using W-Re and PCBN composite tools under well-controlled conditions. Profilometry and optical microscopy were used to quantify the volume loss at the welding tool due to the number of plunges and the welded distance. Torque and transverse force at the welding tool and the welded bead width were measured and related to the wear process. Tool contamination in boron-nitrogen particles and dissolved tungsten was identified at the stir and hard zones, more substantial at the latter. Welding Engineering Department The Ohio State University São Paulo State University (UNESP) Campus of São João da Boa Vista, Av. Profª Isette Corrêa Fontão, 505, Jardim das Flores Metallurgical and Materials Engineering Department University of São Paulo, 10 Av.Prof. Mello Moraes 2463 Brazilian Nanotechnology National Laboratory (CNPEM) Rua Giuseppe Máximo Scolfaro, 10.000 Polo II de Alta Tecnologia de Campinas, CEP PETROBRAS CENPES, Av. Horácio Macedo 950 School of Mechanical Engineering University of Campinas (UNICAMP), Rua Mendeleyev 200 National Institute of Technology – INT SENAI Innovation Institute for advanced manufacturing and microfabrication, Rua Bento Branco de Andrade Filho, 379 São Paulo State University (UNESP) Campus of São João da Boa Vista, Av. Profª Isette Corrêa Fontão, 505, Jardim das Flores Petrobras: 01

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

This research work investigated the influence of friction stir processing under cryogenic treatment on the wear and corrosion behavior of an extruded AZ31B alloy. The experimental work that employed rotational speeds of 800, 1000, and 1200 rpm have been used, keeping the tool feed rate constant at 60 mm/min. The wear mechanism of the AZ31B alloy and cryogenic friction stir processed specimens were studied using a high magnification of SEM images. A lower wear rate was attained under cryogenic conditions which are around 20% better than the base metal. The results revealed the achievement of a lower corrosion rate at the rotational speed of 1000 rpm. The presence of fine grains and the absence of defects in the processed region lead to higher hardness.

Herein, the friction stir processing (FSP) method was adopted to modify the microstructure of as-cast nickel aluminum bronze (NAB). The microhardness, cavitation erosion-corrosion mass loss, morphological damage and electrochemical tests were extensively examined. The results show that FSP can refine and uniform the microstructure of as-cast NAB alloy. FSP NAB alloy displays enhanced cavitation erosion resistance in distilled water and artificial seawater, as well as heightened sensitive to corrosive media in artificial seawater. Quantitative analysis of the synergistic effect between cavitation erosion and corrosion shows that pure cavitation erosion components contributions largest for as-cast NAB. In contrast, FSP NAB is greatly influenced by the synergistic effect component. The damaged surface shows that cavitation erosion mechanisms of as-cast NAB in distilled water and artificial seawater are similar, which is not the case for FSP NAB due to the synergistic effect between cavitation erosion and corrosion.

Friction stir processing is a solid-state welding technology capable of joining metal parts without the melting. The microstructure of the material evolved during the process vary from columnar grain along the thermal gradient in the melt pool to fine equiaxed grains. Evaluation on its mechanical properties in terms of micro-hardness was performed. A significant decrease in microhardness was observed in the processed region. The decrease in the microhardness is mainly attributed to the dissolution of hardening precipitates in the aluminium matrix.

The capability of friction stir processing (FSP) in tensile properties/quality index enhancement of Al–Si–Mg alloys produced by 100% recycling of uncleaned and pre-cleaned machining chips was studied. Toward this end, FSP was applied on as-cast samples under the optimized parameters (rotation and traverse speeds of 2000 rpm and 12 mm/min). The results showed that the as-recycled samples show inferior tensile properties where the quality index of samples prepared by uncleaned chips (7.8 MPa) and pre-cleaned chips (33.7 MPa) is lower than that of sample prepared by virgin A356 ingot (300 MPa). Applying FSP substantially enhanced the tensile properties and quality index of the samples due to the microstructural modification/densification and the elimination of casting defects. For instance, the quality index of the four-pass FSPed recycled sample increased up to 43% compared to that of the as-cast A356 sample prepared by virgin ingots.

Our proposed research works the ideal way was to improve the aluminum alloy material lifetime by incorporating nanoparticle via friction stir processing (FSP) and it was evident from augmenting metallurgical view. The experimental work was carried out by varying tungsten carbide (WC) nanoparticles of 0, 3, 6 and 9 wt% with heat treated aluminium alloy (AA7075-T6) as a matrix through FSP route. The prepared samples were further assessing the metallurgical assessment through microstructure, scanning electron microscope, x-ray diffraction, energy dispersive spectroscopy and electron back-scattered diffraction analysis. The obtained results revealed that the homogeneous distribution of WC nanoparticles in the matrix stir zone having the absence of intermetallic reactions was observed in the microstructure and x-ray diffraction test. The significant degree of grain refinement was observed in the scanning electron microscopy in which composites due to dynamic recrystallization and pinning effect of tungsten carbide particles in the matrix has occurred. Energy dispersive x-ray spectroscopy analysis and scanning electron microscope analysis indicated the presence of tungsten carbide nanoparticles along the processed region in well-defined grain boundaries and its fine spread of grains across the stir zone by dynamic recrystallization. Also, the electron backscatter diffraction study indicated the good distribution of ceramic particles spread across the stir zone. On the whole, a great significance improvement was achieved in metallurgical behavior during the 9 wt% of WC nanoparticles addition in the matrix during the FSP route. These processed surface composites were suggested for automobile and marine components processed in the future.

Submerged Friction stir processing (SFSP) has become apparent as a technique to modify microstructure. It is used to generate refined grains, modify microstructure, achieve superplasticity, synthesize insitu composite and form intermetallic compounds. In this work, AZ31magnesium alloy is friction stir processed at different rotational and welding speed while submerged underwater, cooling oil and brine solution. The effects of different medium on tensile strength, percentage of elongation, hardness, average size of grains in submerged friction stir processed magnesium alloy samples are discussed and the final results are compared. This investigation produces evidence that submerged friction stir processing under coolant oil results in lower peak temperature. During SFSP, water cooling resulted in lower tensile strength when compared to brine solution and coolant oil.

Metal additive manufacturing (AM) processes are used to produce metal parts with greater design freedom and no material wastage from a CAD model, using powder or wire as feedstock with a layer by layer joining of materials by a high intensity energy source such as laser or electron beam. These processes include selective laser melting (SLM), electron beam melting (EBM) and wire arc additive manufacturing (WAAM) techniques which has wide usage in fabricating metal alloys such as aluminum and titanium for the aerospace and automotive applications. However, these AM parts show many limitations in the as built state like poor surface finish and high tensile residual stress, which will affect the mechanical properties and surface integrity because of the usage of high intensity energy-based melting for the fabrication of parts. This give rise to the need for post processing techniques such as heat treatment and additional machining and polishing operations such as shot peening (SP), laser shock peening (LSP), abrasive flow machining(AFM), friction stir processing (FSP) and hot isostatic pressing (HIP) to improve its surface finish, fatigue life and other material properties. This review paper aims to understand the defects of as built AM parts and focus on the post processing techniques employed by the researchers and its effects on the improvement of AM components.

The AA6082-T651 and AA8011-H14 dissimilar aluminium alloys were utilised in this study. The dissimilar aluminium alloys were joined using tungsten inert gas (TIG) welding technique. TIG welding is the most used welding technique for aerospace engineering applications. However, the joining of dissimilar alloys comes with its drawbacks. The friction stir processing technique comes as a microstructural modifying technique to improve the associated joint defects. The TIG-welded AA6082/AA8011 dissimilar aluminium joints were studied comparatively with the friction stir processed TIG-welded AA6082/AA8011 joints. This was done to investigate the impact of the friction stir processing on the microstructure and mechanical properties of the said TIG-welded joints. The results showed that the application of FSP on the TIG-welded joints resulted in a decrease of minimum grain size of 12.41 to 3.68 µm. The ultimate tensile strength increased from 86.9 to 90.2 MPa. The stir zone hardness also increased from 55 to 68 HV.

Magnesium (Mg) alloys known to have the lowest density amongst other engineering materials used for structural applications. They are emerging as a promising material, particularly in automotive and aerospace industry. But the poor wear characteristics of Mg alloys restrict their use in many applications. In the present investigation, friction stir processing (FSP) of as-cast AZ91D Mg alloy was performed with the objective to improve its wear properties. The FSP was carried out at a tool rotation speed (TRS) of 600, 900 and 1200 rpm. The tool travel speed was kept constant at 70 mm/min. A pin-on-disc tribometer was used to perform dry sliding wear experiments at an optimized set of parameters. FSPed specimens demonstrate a substantial grain refinement and decomposition of coarse β-Mg17Al12 particles into Mg matrix. At a TRS of 600 rpm, the average grain size was reduced to 25 μm and the microhardness was increased to 81 Hv. The refined microstructure and improved hardness are expected to have provided better wear resistance in FSPed samples.

The demand for fine-grained structure materials has been increasing for the last two decades due to their superior mechanical properties such as enhanced superplasticity, high strength to weight ratio and excellent corrosion resistance. The present study focuses on the production of bulk-area stir zone in aluminium 6061alloy with aid of cryogenic friction stir processing (FSP). For this aim, process parameters such as tool traverse speed and rotational speeds were selected from trial experiments. With the use of optimum process parameters, FSP was conducted in cryogenic media. Optical 3D microcope, and universal testing machine were employed to characterize the processed samples and results have been reported.

The main aim of the study is to investigate the effect of the corrosion behaviour of Friction Stir Processed (FSPed) AZ91 magnesium alloy. The corrosion testing was performed by immersing the FSPed samples in 3.5 % (by weight) sodium chloride (NaCl) solution. It is originally proved that the corrosion rate of AZ91 FSPed samples decreased significantly with a square pin profile as compared to the round pin profile. It is attributed that the pulsation effect of the flat-faced tool helped to improve the flow of material. Also, Friction Stir Processing (FSP) modified the surface morphology and uniformly distributed the β-Mg17Al12 phase particles that helped in improving the corrosion rate of AZ91 alloy.

Conventional fusion weld joint possesses coarse grain structure, inevitable defects which results in inferior weld properties. To overcome this, the welds are often repaired or processed with post welding treatments. Friction stir welding (FSW) being solid state process avoids issues related to the solidification of the conventional weld. FSW joint also exhibits the need for improved weld properties. The variant process of FSW, friction stir processing (FSP) modify the microstructure of material for property improvement. FSP can be used to modify welded joints which in addition to modify the microstructure. It also eliminates defects if followed to the fusion welding process. The friction stir processed (FSPed) weld joint is expected to exhibit improved mechanical properties and corrosion resistance. This paper review recent research trends related to the use of FSP for weld modification and its effect on weld properties. It also briefs the different welding processes and parameters used. The last section summarises the scope for FSP and its variants for weld modification.

In past decades, Aluminum composites have found their application in aerospace and automobile sectors. Because of their high strength to weight ratio and low density, they have been used in different areas to replace the application of iron and steels. Researchers to fabricate aluminum composite have used different types of reinforcing materials like Nano tubes, ceramics and different types of fibers. This work represents the fabrication of aluminum composite reinforced by fly ash. Fly ash with different weight percent (0 wt%, 1 wt%, 2 wt% and 4 wt%) have been reinforced in aluminum matrix through friction stir processing. Results of tests have proclaimed that with increase in percentage of fly ash in aluminum matrix, mechanical and tribological properties have enhanced. Composite with 2 wt% fly ash has shown the best results among all the fabricated composites.

Super duplex stainless steels (SDSS) are used in offshore applications and oil/gas plants operating under severe service conditions due to their superior mechanical and electrochemical properties. Fracture toughness, wear and corrosion resistance of a material depends largely on its microstructure and can be improved by refining the latter. Friction stir processing (FSP) can be employed to refine the microstructure of the material, resulting in superior fracture toughness, wear, and corrosion resistance. In the present research, SAF 2507 SDSS was subjected to FSP with optimized processing parameters to study the influence of FSP on fracture toughness, wear, and corrosion resistance of the material. It was observed that FSP refined alloy grains by decreasing the grain size from an average of 160 µm in the base metal to 2-30 µm in the stir zone. Refinement of grains increased the hardness of the material, which enhanced its wear resistance by more than 15%. Wear track and debris analysis revealed the change in wear mechanism of the processed material. FSP also modified the surface composition of processed material, which served to improve its corrosion resistance by more than 80%. Morphology of the corroded surfaces of base and processed material showed that the processed material was more resistant to corrosive attacks than base material. FSP enhanced the grain boundaries in the processed region which improved the fracture toughness after exposure to accelerated corrosion by about 26%. Fractographic study revealed that processed material had brittle fracture behavior while base material had ductile fracture behavior.

The structure of samples of the C27400 copper alloy coatings on the AA5056 aluminum alloy surface, produced by friction stir processing of a rolled sheet package is studied. The regularities of the structure formation at deformation-initiated mixing of Al–(Cu, Zn) system components are elucidated. Intensive diffusion and mechanical mixing of the Al–(Cu, Zn) system components is revealed, resulting in the formation of a complex structure of the stir zone on the macrolevel. It is established that during the formation of the structural-phase composition of the coating, the solid aluminum solutions are formed in copper by zinc extrusion from the solid solution together with complex solid solutions and intermetallic phases by zinc diffusion into the aluminum lattice.

In this paper, the wear resistance of the different parameter (the tool rotation speed and feed speed) modified layer of the hot rolled 7075 aluminum alloy by the friction stir processing (FSP) were studied. The wear mechanism was explored by analyzing the surface morphologies of the modified layer after wear. The results showed that the wear resistance of 7075 aluminum alloy modified by FSP was superior to that of the base metal at different temperatures. The comprehensive wear resistance was better when the tool rotation speed and the feed speed were 500 rpm and 60 mm/min under different temperatures. Furthermore, the FSP parameters had a significant influence on the wear resistance of the modified layer. When the FSP parameters were too high or too low, the wear resistance would be reduced and the adhesive wear would appear. In addition, the modified layers obtained by different parameters received poor wear resistance when the temperature at high values.

The present work deals with the formation and stabilization of the 18R lamellar long-period stacking order phase (LPSO) through friction stir processing of a GWZ magnesium alloy. In this regard, the formation sequence was investigated in detail, where the metastable LPSO structures were formed in the matrix and then transformed into the 18R structure. The involved micro-mechanism is also discussed with emphasis on the formation of a GP-like zone using high-resolution transmission electron microscopy.

Al-Zn-Mg-Sc alloys with different grain structures were fabricated using friction stir processing (FSP) and rolling with different routes. The hot rolling (HR) sample after T6 treatment exhibited stronger texture than the other three samples, and the T6 FSP samples exhibited the finest grains, with average grain size (AGS) of 5 μm. Cold or hot rolling before T6 treatment led to grain coarsening in the T6 FSP samples, and the AGS in the T6 FSP + HR reached 126 μm. All the samples exhibited a low density of dislocations and contained coarse grain boundary precipitates, Al3(Sc,Zr) phases, and a high density of η′ phase. The T6 HR sample exhibited the highest strength mainly due to its strong texture and reasonable grains size, and the T6 FSP sample exhibited the highest ductility due to its fine equiaxed grain structure, which can promote the redistribution of stresses and prevent strain localization during the tension process.

Magnesium alloys are widely used to lightweight the components in the automobile, aerospace, and electronics industries because of their low density and high specific strength. However, factors lik...

Friction stir processing (FSP) can play an important role in grain refinement, redistribution of second phase and texture evolution. In this study, different rotation speed was employed during FSP ...

Effect of strain rate on the tensile behavior of two friction stir-processed dual-phase high entropy alloys was investigated. The dual-phase high entropy alloys have a high fraction of metastable f.c.c. phase. Engineering the f.c.c. phase metastability through alloy chemistry leads to different levels of transformation and impacts the retained f.c.c. phase after deformation. These metastable high entropy alloys show dominance of transformation-induced plasticity (TRIP) irrespective of strain rates, unlike the observations in TRIP steels.

Mechanical alloying can be carried out by a method known as friction stir processing, whereby solid Zn particles in a solution are distributed onto an aluminium alloy plate. The aim of this study was to determine the effects of a volume of Zn particles on the mechanical and physical properties of aluminium 1xxx alloy that had been subjected to friction stir processing. The specimens were plates composed of 1xxx series aluminium. A groove, measuring 12 mm in diameter, was pierced to various depths, and the Zn particles in these containers were then subjected to friction stir processing using a pin-less tool with a diameter of 15 mm. The results showed that the highest hardness was found in the uppermost layer of the workpiece, and this gradually decreased with thickness. An increase in the amount of Zn particles caused an increase in material hardness. The highest hardness of 87.1 HV in the friction stir-processed AA1100 was obtained at the highest volume of Zn compared to the hardness of 44.5 HV, which was obtained for the specimen without the addition of Zn.

Hybrid nanocomposites have potential as wear-resistant materials. However, synthesizing these nanocomposites by conventional molten state methods result in agglomeration of reinforcements. To mitigate this issue, in the current study hybrid aluminum nanocomposites were synthesized using friction stir processing (FSP). For this, two blends of titanium and graphite particles were used as reinforcements. These composites were characterized using a stereo microscope, scanning electron microscope, electron probe micro analyzer, X-ray diffraction, and microhardness indenter. During FSP, ternary carbide (Ti3AlC2) and intermetallic (AlTi3) were formed in situ. These compounds improved the hardness of the composites up to four times. Further, these in situ composites were subjected to wear test using pin-on-disk tribometer at various sliding speeds. Polycrystalline alumina disks were chosen as counterface to minimize chemically induce wear. The wear rate of the composites was 5 to 13 times lower than that of the base metal. This excellent resistance to wear in composites was attributed to improved resistance to abrasion and delamination. Furthermore, it was seen that the dominant wear mechanism of the composites changed from abrasive to adhesive wear as the sliding speed increased.

Magnesium alloy AE42 is a candidate material for high-temperature applications. However, as-cast AE42 alloy exhibits poor high-temperature creep properties because of the microstructure that shows a continuous network of β-Mg17Al12 and Al-RE precipitates along the boundaries of coarse α-Mg grains. In the current work, friction stir processing technique was adopted to refine the coarse as-cast structure of the AE42 alloy and break up the continuous network of β-Mg17Al12 and Al-RE precipitates. The creep properties of the parent material and friction-stir-processed specimens were determined by impression creep test at 150, 175, 200, 225 and 250 °C. The results demonstrated that the presence of fragmented precipitates and the elimination of continuous network structure improved the creep resistance of the AE42 alloy. The metallurgical analysis revealed that no new precipitates were formed after friction stir processing and creep testing. From the data, it can be concluded that friction stir processing of AE42 alloy can lead to an increase in service temperatures from 150 to 225 °C.

The present paper studies the influence of different cooling media (water and cryogenic media) on microstructure, mechanical, and corrosion behavior of friction stir processing of AA2014. From the electron backscattered diffraction results, it was observed that the grain size in stir zone of air-cooled friction stir processing, dry ice-cooled friction stir processing, and underwater friction stir processing are 4.9 µm, 3.5 µm, and 0.9 µm respectively, and the fraction of high angle grain boundaries are more in underwater friction stir processing sample compared to other conditions. The ultra-fine grained structure (0.9 µm) was achieved in underwater friction stir processing due to uniform heat dissipation from the processing zone to the water. Mechanical properties such as hardness and strength were improved in underwater friction stir processing compared to other conditions. The fine precipitates formed in the underwater friction stir processing sample were distributed randomly at grain boundaries, and hence corrosion resistance was improved in underwater friction stir processing sample compared to other conditions.

In this work, the effect of friction stir processing (FSP) on microstructure and mechanical properties of an Al-5Mg-0.2Sc-0.1Zr alloy was investigated in detail. The results showed that the as-cast alloy exhibited equiaxed grain structure with a large number of primary Al3(Sc,Zr) particles inside. FSP imposed a significant grain-refining effect on the alloy, changing the average grain size of 50.5 μm to 2.4 μm, which is attributed to the occurrence of dynamic recrystallization and generation of nanoscaled Al3(Sc,Zr) precipitates. These Al3(Sc,Zr) dispersoids intense impeded the movement of dislocation and grain boundaries and hindered the growth of recrystallized grains, resulting in a remarkable grain-refining strengthening, substructure strengthening and precipitation strengthening effect. On the other hand, the residual primary Al3(Sc,Zr) particles gave rise to a loss in ductility.

The stress corrosion cracking behavior of friction stir processed, micro arc oxidation coated and a composite coated (friction stir processed-micro arc oxidation) ZE41 magnesium alloy were studied in modified simulated body fluid (m-SBF) solution at room temperature. Friction stir processing was carried out with a tool rotation speed of 650 rpm and a traverse speed of 50 mm/min. The results showed that fine equi-axed grain structure with an average grain size of ∼2.8 µm, fragmentation, and partial dissolution of T-phase and Zr-rich particles was achieved through friction stir processing. Specially designed two electrode coating method was adopted to produce samples with micro arc oxidation coating in silicate solution. The stress corrosion cracking susceptibility of base metal, friction stir processed, micro arc oxidation, and composite coated friction stir processed-micro arc oxidation samples were evaluated through constant load testing at five different stress levels. The results indicated higher stress corrosion cracking susceptibility for base metal compared to friction stir processed; micro arc oxidation and friction stir processed-micro arc oxidation samples. Grain refinement and microstructure homogenization enhanced stress corrosion cracking resistance of friction stir processed sample whereas the barrier effect of coating during initial stages of corrosion improved stress corrosion cracking resistance of micro arc oxidation sample compared to base metal. Among all the samples, friction stir processed-micro arc oxidation exhibited superior stress corrosion cracking resistance due to the self-repairing mechanism of friction stir processing, which in turn improved the corrosion resistance of micro arc oxidation layer. The fractographic features revealed different stress corrosion cracking mechanisms for base metal, friction stir processed, micro arc oxidation, and friction stir processed-micro arc oxidation samples. T-phase and Zr-rich particles played major role in the initiation of corrosion pits and resulted in stress corrosion cracks.

The effect of Zn–40Al–2Cu–xSi (x = 4 and 8 wt-%) tungsten inert gas (TIG) surfaced coatings and multi-pass friction stir processing (FSP) on the tribological properties of Zn–40Al–2Cu alloy was stu...