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Friction Stir Processing: A New Grain Refinement Technique to Achieve High Strain Rate Superplasticity in Commercial Alloys
Abstract
Friction stir processing is a new thermo-mechanical processing technique that leads to a microstructure amenable for high strain rate superplasticity in commercial aluminum alloys. Friction stirring produces a combination of very fine grain size and high grain boundary misorientation angles. Preliminary results on a 7075 Al demonstrate high strain rate superplasticity in the temperature range of 430-510 °C. For example, an elongation of >1000 % was observed at 490 °C and 1×10-2 s-1. This demonstrates a new possibility to economically obtain a superplastic microstructure in commercial aluminum alloys. Based on these results, a three-step manufacturing process to fabricate complex shaped components can be envisaged: cast sheet or hot-pressed powder metallurgy sheet + friction stir processing + superplastic forging or forming.
... In this case, the processing must be done below the material's melting point to avoid these problems. The friction stir process (FSP) is one such solid-state processing technique developed by Mishra et al [11][12][13] for surface modification of metallic materials. ...
... The fitted model of hardness is given by equation no. (12). It was found that as-cast NAB exhibited 7.0×10 -6 gm m −1 of wear rate, whereas the FSPed composite showed a minimum wear rate of 5.5×10 -6 gm m −1 . ...
Present study focuses on fabricating a chromium-reinforced nickel aluminum bronze (NAB) composite using an optimized multi-pass friction stir processing (FSP) technique. The tool rotation, traverse speed, and volumetric concentration of the reinforcement were taken as input process parameters, whereas the ultimate tensile strength, yield strength, percentage elongation, microhardness, and sliding wear rate were taken as output responses. Taguchi-Grey relational analysis (GRA) was used to optimize the input process parameters, which were 1000 r.p.m., 28 mm/min and 15.7 %, respectively. The most significant parameter was traverse speed, followed by tool rotation and volumetric concentration. The fabricated composite exhibited improved mechanical and tribological performance compared to the NAB base alloy owing to grain refinement. FE-SEM, EDS, and XRD analyses were performed on the as-cast NAB, chromium powder and FS processed composite. Grain refinement was significant in the FSPed region of the composite. Microstructural examination was carried out on the fractured specimens of the NAB base material and composite. Furthermore, the worn surfaces of the specimens were examined to investigate their wear mechanisms. It was revealed that the mechanism of wear in the case of as-cast NAB was primarily adhesion, whereas abrasion was found to be the primary mechanism of material removal in the processed composite.
... FSW is used for joining, while FSP is used for modification in the grain structure of the material. Friction stir processing (FSP) was developed by Mishra and Mahoney [13] to process a single piece of material. In FSP, a rotating tool mechanically stirs the material to alter its microstructure. ...
... Severe plastic deformation occurs during FSP as the pin mechanically stirs the material to alter its microstructure. Grain refinement of the microstructure of the material occurs due to the plastic deformation and different researchers showed that it occurs through dynamic recrystallization of the material [13,14]. Ultrafine size grains can be formed by this process. ...
Friction stir processing (FSP) technology has received reasonable attention in the past two decades to process a wide range of materials such as aluminum, magnesium, titanium, steel, and superalloys. Due to its thermomechanical processing nature, FSP is used to alter grain structure and enhance mechanical and corrosion behavior in a wide range of steels. The refinement in grains and phase transformations achieved in steel after FSP affects hardness, tensile properties, fracture toughness, fatigue crack propagation rate, wear resistance, and corrosion resistance. A number of review papers are available on friction stir welding (FSW) or FSP of nonferrous alloys. In this article, a comprehensive literature review on the FSP/FSW of different types of steels is summarized. Specifically, the influence of friction stir processing parameters such as advancing speed, rotational speed, tool material, etc., on steels’ performance is discussed along with assessment methodologies and recommendations.
... In practical applications, Al-7075 alloy are inevitably faced challenges during processing with existing conventional techniques, most notably metal cladding, surface nitriding and different types of heat treatment processes, cannot be used so effectively [2]. Friction stir processing (FSP) is the newly invented technique which improves the strength and ductility by making the grains finer and uniformly dispersion [3]. Therefore, it is considered that FSP would be a potential technique which improves the grain structure the ductility and strength as well as lesser time production and cost [4,5]. ...
... As the number of FSP passes increases, the formation of intermetallic compound increases which enhances the surface properties. Studies are recorded primarily on the manufacture of nanocomposites Al-Al 3 Fe, Al-Al 3 Ti, Al-Al 3 Ni, and Al-Al 2 Cu through Al-Ti, Al-Fe, Al-Ni, and Al-Cu FSPed coated surface. In addition to oxide structures such as Al-CeO 2 , Al-CuO, Al-TiO 2 , and Al-MgTiO 2 , in-situ nano-size Al 2 O 3 and MgO particles was also identified. ...
Friction stir processing (FSP) is a new and exciting technique being extensively explored because of its thermomechanical
surface modification which has the capability to enhance the mechanical, microstructural and tribological
properties. Various studies were described on friction stir processed aluminium alloys using several
reinforcement particles containing micro and nano size grains thereby the formation of homogeneous and
identical microstructure. However, this review is mainly focused on Al-7075 alloy which is a potentially superplastic
alloy for making metal matrix composites. In this review, the recent research progress in FSP is
discussed in detail with particular emphasis on their preparing method, characterization and various mechanical
properties including present challenges and future prospects. Though, a remarkable progress has been made
during the past few years, the present status in materials processing is far from ideal, especially in obtaining
desire composites by using single or dual reinforcements.
... The high thermal conductivity of pure copper could explain the absence of the HAZ in Fig. 6. The synergetic effect of the mechanical forces and elevated temperature beyond Tm/2 (where Tm denotes the melting point of the cooper) created an irregular arrangement of the grains known as a thermos-mechanically affected zone [46]. ...
... The processed samples were seen to be composed of uniaxial grains that were much smaller than those in the as-received pure copper. The sever plastic deformation (SPD) occurred upon the FSP [41] leads to highly deformed microstructure with finer grains, thereby enhancing the mechanical properties of the specimen [46]. The dynamic recrystallization (DRX), which occurs during the FSP process [47], causes a refined microstructure [48], with the extents of grain refinement and grain growth phenomena determining the final microstructure. ...
Multiple passes of the friction stir processing (FSP), were applied on the pure copper substrates. As reinforcements, Ti2AlC and MoS2 nanoparticles were employed for developing pure copper matrix surface nanocomposites. To investigate the microstructural evolution of the samples upon the FSP, optical microscopy (OM) and scanning electron microscopy (SEM) were utilized. Considerable microstructural grain refinement was achieved in the samples subjected to the FSP. To evaluate the hardness of the samples, the Vicker's microhardness method was used. Accordingly, the average microhardness of the Cu/MoS2 and Cu/Ti2AlC nanocomposites increased by about 38% and 55%, respectively, as compared to the non-reinforced sample. The samples were further subjected to uniaxial tensile test to assess their mechanical properties. The ultimate tensile strength (UTS) values of the base metal (BM) and Cu/Ti2AlC nanocomposite samples subjected to 4-pass FSP, were improved by nearly 75% and 175%, respectively. To investigate the tribological behavior of the samples, the dry sliding wear test was carried out by the AISI 52100 steel counterpart. The mass losses of the Cu/MoS2 and Cu/Ti2AlC nanocomposites were about half of the pure copper base metal, and the average friction coefficient decreased by 20% and 32% for the Cu/Ti2AlC and Cu/MoS2 nanocomposites, respectively. SEM investigations on the worn surface and the debris generated by the wearing of the samples after the 300 m sliding wear test, indicated the occurrence of the adhesion and delamination mechanisms in the case of the non-reinforced samples, while abrasion and delamination were the dominant mechanisms for the composites samples.
... Overall, the microstructural changes are governed by the grain refinement of the SZ. The grain refinement is one of the prominent advantages of FSP which controls the mechanical, tribological and physical properties of the material [73][74][75]. FSP is also famous as a tool for microstructural modification through severe plastic deformation (SPD) [75]. The traditional methods of SPD such as accumulative roll bonding (ARB), equal channel angular pressing (ECAP) have their limitation due to low strain rate and reduced cross-sectional area of the workpiece material [16]. ...
... The grain refinement is one of the prominent advantages of FSP which controls the mechanical, tribological and physical properties of the material [73][74][75]. FSP is also famous as a tool for microstructural modification through severe plastic deformation (SPD) [75]. The traditional methods of SPD such as accumulative roll bonding (ARB), equal channel angular pressing (ECAP) have their limitation due to low strain rate and reduced cross-sectional area of the workpiece material [16]. ...
The demand for tailored properties of the materials and lightweight characteristic accelerates the development of metal matrix composites (MMCs). The conventional methods of MMCs development require several post-processing techniques like a microstructural modification or grain refinement, to fulfil the desired requirement of specific applications. In this regard, friction stir processing (FSP) can be proved as an alternative, not only for microstructural modification but also utilized for the development of surface composites. This solid-state approach is an environment-friendly process. It also refines the grain structure of the alloys and composites, which in turn, enhances the mechanical properties such as tensile strength, hardness and fatigue strength. The present work aims to focus on the state of the art research in the field of friction stir processing and to highlight its key points and merits over traditional methods. The present work also emphasizes the developments in friction stir processing, especially on aluminium and magnesium-based alloys and composite and futuristic approaches adopted in various industrial application.
... Thus, there exists a variety of literature whose major concern was to obtain desire mechanical properties i.e. tensile strength and hardness, better resistance towards wear and corrosion, homogenous distribution of secondary phase particles and attaining superplasticity in manufactured surface composites and to optimize process parameters [125][126][127][128][129]. It should also be noted that friction stir processing has been implemented for modification of microstructure and thus enhancing the mechanical properties of the bulk composites [102,103,130,131]. ...
Owing to its excellent properties, Metal Matrix Composites (MMC) has gained popularity and finds application in aerospace, aircraft, shipbuilding, biomedical, biodegradable implant materials and many more. To serve the industrial needs, the manufactured MMC should have homogenous distribution along with minimum agglomeration of reinforcement particles, defect-free microstructure, superior mechanical, tribological and corrosive properties. The techniques implemented to manufacture MMC highly dominate the aforementioned characteristics. According to the physical state of the matrix, the techniques implemented for manufacturing MMC can be classified under two categories i.e. solid state processing and liquid state process. The present article attempts to review the current status of different manufacturing techniques covered under these two categories. The article elaborates on the working principles of state-of-the-art manufacturing techniques, the effect of dominating process parameters and the resulting characteristic of composites. Apart from this, the article does provide data regarding the range of dominating process parameters and resulting mechanical properties of different grades of manufactured MMC. Using this data along with the comparative study, various industries and academicians will be able to select the appropriate techniques for manufacturing MMC.
... The mechanical properties of these, and other, alloys can be improved using severe plastic deformation (SPD) as an effective tool for the production of ultrafine-grained material. The most important SPD techniques are friction stir processing [3,4], high-pressure torsion (HPT) [5,6], accumulative roll bonding (ARB) [7,8] and equal channel angular pressing (ECAP) [9,10]. ...
A commercial 2024 aluminum alloy was heat treated at 280 °C for 48 h and then slow cooled in a furnace to obtain minimum hardness. This material was then friction stir processed (FSP) using three sets of processing conditions. To study the effect of the processing on the microstructure and the high temperature mechanical properties, the materials were tested in tension at an initial strain rate of 10−2 s−1 and temperature range 200 to 450 °C. Processing severity was selected as the main factor for obtaining fine grain sizes right after FSP. The grain size was enormously reduced from about 50 µm to 1 µm. This grain reduction gave rise to very high elongations to failure of about 400%. Strain–rate-change tests showed a stress exponent close to 2 at intermediate strain rates, which was related to grain boundary sliding as the controlling deformation mechanism and to superplasticity, which is strongly grain-size dependent. A possible controlling deformation mechanism by solute-drag creep, as proposed by other authors, was disregarded since tests conducted at 450 °C, where the microstructure of the FSP materials coarsens rapidly, gave a low elongation to failure and high resistance, which showed the importance of the grain size dependence of the operative deformation mechanism at 250–400 °C, which was only compatible with grain boundary sliding.
... Friction Stir Processing (FSP) is an evolving technique to produce surface composite and achieve super plasticity [1]. It was developed in 1999 by Mishra et al. [2]. ...
Aluminum alloys are among the most widely used material in the manufacturing industries due to their high strength and lightweight properties. To enhance its surface properties, Friction Stir Processing (FSP) proved itself as an efficient method to enhance its microstructural, mechanical, and tribological properties. However, FSP has many process parameters that can affect the final properties of the material. Therefore, an optimized process parameter is required before the use of FSP to obtain the best results. In this paper, a mathematical model has been developed using Response Surface Methodology to predict the hardness of produced surface composite of AA5083 aluminum alloy by using SiC-Gr hybrid reinforcement. FSP was optimized for its hardness (HRB) property by optimizing the FSP process parameters like Tool rotating speed, Tool Traverse speed, number of FSP passes, and the ratio of hybrid reinforcement volume fraction. It was found that the Tool Rotating speed of 1000 rpm, traverse speed of 80 mm/min, 3 number of FSP passes, and Hybrid reinforcement ratio of 75:25 (SiC:Gr) produced the best result with the hardness of 32.6HRB.
... Friction stir processing (FSP) is a novel grain refinement technique and one of the most promising methods of modifying the microstructure and properties of engineering materials. This solid-state processing technique was developed by Mishra et al. [1,2], but the basic principles and idea of friction stir processing are derived from friction stir welding (FSW) technology [3]. The differences between FSP and FSW mainly concern their purpose because FSW technology is used to join materials [4,5], while FSP is employed to modify the microstructure of the material [6][7][8][9]. ...
A rolled plate of 7075 aluminum alloy was friction-stir-processed (FSP) with simultaneous cooling by an air stream cooled to −11 °C with a jet cooling nozzle. Two variants of air blowing were used: at an angle of 45° to the sample surface and at an angle of 90°. The reference material was a sample subjected to analogous treatment but naturally cooled in still air. The microstructural tests revealed strong grain refinement in all the samples, with higher grain refinement obtained in the air-cooled friction-stir-processed samples. For the naturally cooled samples, the average grain size in the near-surface area was 7.6 µm, while for the air-cooled sample, it was 1.4 µm for the 45° airflow variant and 3.2 µm for the 90° airflow variant. A consequence of the greater grain refinement was that the hardness of the air-cooled friction-stir-processed samples was higher than that of the naturally cooled samples. The improvement in abrasive wear resistance was achieved only in the case of the friction-stir-processed specimens with air cooling. It was found that the change in the air blowing angle affects not only the degree of grain refinement in the stirring zone, but also the geometrical structure of the surface. In all the samples, FSP caused redistribution of the intermetallic precipitates combined with their partial dissolution in the matrix.
... In more detail, all the technologies presented will be considered in other study. [6][7][8][9][10][11]. Among Russian studies, there are few works devoted to FSP [12,13]. ...
One of the most perspective methods of hardening is friction stir processing. The study shows processing methods based on the friction stir principle. The results of hardening of tool steels 1089 (Fe97%, C0.8%), 3343 (Fe80%, C0.9%, Cr4%, Mo5%, W6%, V2%), 440C (Fe78%, Cr18%, C0.95%) are presented. As a result of hardening, it was possible to increase the microhardness of carbon tool steel by more than 3 times, and also to achieve a decrease in the average grain size in the treated area by more than 10 times in relation to the base material. It is proposed to use the FSP in the manufacture of cutting tools from tool steels to increase physical and mechanical properties.
... Friction stir processing (FSP), stemming from the stir friction welding (FSW), is an efficient and simple process to achieve material grain refinement and property improvement by large plastic deformation [10]. In FSP, the stirring tool is used to process the material at a certain rotation and feeding speed [11]. The material undergoes severe plastic deformation, while the tool friction heat makes the material reach the recrystallization temperature. ...
A dual-phase Mg-Li alloy LA103Z sheet was subjected to single pass submerged friction stir processing (FSP) at various of tool sizes, rotation rates and travel speeds. The relationships between processing parameters, frictional heat generation, microstructure, and the room-temperature tensile properties of LA103Z in the stir zone were systematically investigated. Both the α-Mg phase and the β-Li phase undergo complete dynamic recrystallization, the grains are significant refined and the texture is significantly weakened. The precipitation of the AlLi phase and the Li2MgAl phase are promoted by FSP. With the increase of the tool size and rotation rate, the average grain size of the FSPed LA103Z rises as well as the tensile strength, showing an inverse Hall-Petch relation. This is owing to the solid-solution strengthening effect and the reduction of the α/β phase boundaries caused by the dissolution of the α-Mg phase. After being processed by a 16mm-diameter-shoulder stirring tool under the rotation rate of 800rpm and the traverse speed of 100mm/min, the ultimate tensile strength of the FSPed LA103Z is remarkably improved from 177.92MPa (base metal, BM) to 268.04MPa, showing the best mechanical property.
... Aluminum matrix composites have been a subject of great interest in the field of sports, electronic packaging, military, aerospace and automotive industry due to their low cost and enticing properties [1,2]. Compo-casting, stir casting, squeeze casting, powder metallurgy, metal injection molding are the various methods by which composite can be fabricated [3]. However, all these fabricating methods results into nonuniform distribution of the reinforcement, which is quite undesirable. ...
The effect of FSP process parameters such as mechanical, microstructural and wear behaviour on A7075/WC surface composites was examined. In the present investigation, 15 wt% WC was used as a reinforcement for producing FSP surface composite through cylindrical tapered tungsten carbide pin tool. It was observed that WC reinforced FSPed surface matrix under traverse speed of 60 mm/min with 1200 rpm rotational speed reduced the matrix particle’s size and distributed homogeneously throughout the surface. Also, as the FSP passes increases the broadening and offsetting of the diffraction peaks of WC and A7075 was observed. At same process parameters corresponding to 6- passes, the micro hardness as well as tensile strength were increased up to 35% and 52%, respectively, compared to base material (A7075). In addition, the increase in FSP passes increases both slurry erosive wear resistance and abrasive wear resistance due to repeated self-heat treatment phenomena.
... The process parameters in FSP are tool material, tool rotational speed, transverse speed, tool profile, reinforcement materials, etc., which are shown in Fig. 2. Tool transverse speed and rotational speed determine the heat produced in the material [17]. The heat produced determines the formation of stir zone [19] and grain refinement. The maximum temperature achieved in stir zone is reported below melting point of material and ranged in (0.6-0.9) Tm. ...
Friction stir processing (FSP) is a technique to manufacture metal-matrix composites (MMCs) and has been gained popularity as a promising surface fabrication technique as it is a solid-state and eco-friendly process. FSP is used to fabricate composite by eliminating various casting defects, improving the grain refinement, increasing the hardness and wear resistance, tensile strength, corrosion resistance, etc. A rotating tool is inserted into the workpiece, due to which frictional heat is generated, which softens the material. Due to the stirring action of the tool pin, the reinforcement particle is mixed with base material in the stir zone, and the tool shoulder applies an axial downward force to constrained the plasticized material. This review paper focuses on friction stir processing parameters that directly affect the quality of fabricated surface composites. Microstructural and mechanical characterization, including microhardness, tensile strength, wear, corrosion, is also discussed.
... The microstructure and properties of magnesium alloys can be additionally shaped by means of a wide range of volumetric and surface treatments, including, e.g., technologies using concentrated heat sources such as lasers [2][3][4][5] or GTAW technology [6]. One of the latest solutions, which is becoming increasingly important in surface engineering, is the innovative friction stir processing invented by Mishra et al. [7,8]. It is a new solid-state surface modifying technique that has been widely used for grain size refinement. ...
Friction stir processing (FSP) was used to modify the surface layer of the AZ91 magnesium alloy. The treatment was carried out using a jet cooling nozzle, generating a stream of cold air and enabling intensive cooling of the friction stir processed (FSPed) zone. Single-pass FSP was carried out using a tool rotational speed of 500 rpm and travel speed of 30 mm/min. The treatment was conducted using a truncated cone-shaped tool with a threaded side surface. Strong grain refinement and microstructural changes typical for FSP were found in all the samples. Very fine, equiaxed recrystallized grains dominated in the stirring zone. In the samples modified with the jet cooling nozzle, greater grain refinement was obtained than in the case of naturally cooled material. The average grain size in the surface part of the stirring zone was 1.4 μm and 9 μm in the samples with air-cooling and with natural cooling, respectively. Both the naturally cooled specimen and air-cooled specimen were characterized by a distinctly higher hardness than the base material. The average Vickers hardness in the stirring zone was 91 HV0.1 in the FSPed sample with the air-cooling system and 85.5 HV0.1 with natural cooling, respectively. The average Vickers hardness of the as-cast alloy was 64 HV0.1. Slightly higher wear resistance of the FSPed samples using a jet cooling nozzle was found in relation to the naturally cooled sample. Based on the conducted research, high efficiency of the jet cooling nozzle in cooling the modified zone during friction stir processing was found.
... technologies using concentrated heat sources such as lasers [2][3][4][5] or GTAW technology [6]. One of the latest solutions, which is becoming increasingly important in surface engineering, is the innovative friction stir processing invented by Mishra et al. [7,8]. It is a new solid-state surface modifying technique that has been widely used for grain size re nement. ...
Friction stir processing (FSP) was used to modify the surface layer of the AZ91 magnesium alloy. The treatment was carried out using a jet cooling nozzle, generating a stream of cold air and enabling intensive cooling of the friction stir processed (FSPed) zone. Single-pass FSP was carried out using a tool rotational speed of 500 rpm and travel speed of 30 mm/min. The treatment was conducted using a truncated cone-shaped tool with a threaded side surface. Strong grain refinement and microstructural changes typical for FSP were found in all the samples. Very fine, equiaxed recrystallized grains dominated in the stirring zone. In the samples modified with the jet cooling nozzle, greater grain refinement was obtained than in the case of naturally-cooled material. The average grain size in the surface part of the stirring zone was 1.4 µm and 9 µm in the samples with air cooling and with natural cooling, respectively. Both the naturally-cooled specimen and air-cooled specimen were characterized by a distinctly higher hardness than the base material. The average Vickers hardness in the stirring zone was 91 HV0.1 in the FSPed sample with the air-cooling system and 85.5 HV0.1 with natural cooling, respectively. The average Vickers hardness of the as-cast alloy was 64 HV0.1. Slightly higher wear resistance of the FSPed samples using a jet cooling nozzle was found in relation to the naturally-cooled sample. Based on the conducted research, high efficiency of the jet cooling nozzle in cooling the modified zone during friction stir processing was found.
... After FSW's success in joining similar materials in butt configurations, various other variants of the process came into existence based on different application requirements. Some major variants comprise of Friction Stir Spot Welding (FSSW), Friction Stir Processing (FSP), dissimilar FSW, and Micro-friction Stir Welding (μFSW), among others for applications in spot welding of sheets in automotive sectors, improving material properties for engineering components, TWBs in automotive industries and joining of micro-mechanical assemblies, respectively [2,[11][12][13][14]. Among these variants, dissimilar welding is an essential variant for application in many sectors because of its increased performance and functionality. ...
Dissimilar micro-friction stir welding (dissimilar μFSW) can be a preferred choice for joining dissimilar materials having thickness ≤ 1000 μm. The technique's potential applications are in miniaturized components, where the inherent benefits of the process, such as low temperature, low distortion, and clean joining, are advantageous compared to fusion welding. However, the challenges associated with dissimilar μFSW hinder its full potential applications in the relevant industries. The challenges are particularly a combination of two different characteristics of the process (i) the complexities of simultaneously fulfilling the dissimilar materials' demands due to the vast differences in the two materials' mechanical and thermal properties and (ii) the problems due to reduced sheet thickness. In this regard, the present work is a comprehensive
and timely review of the research works done on dissimilar μFSW targeted at easily acquainting the research community about the know-how and the state of the art of the process. The review is broadly divided into three crucial parts: the process inputs/requisites, process mechanics, and process performance. The details about the μFSW tool, process parameters, and relative sheet positioning are discussed under the heading process inputs/requisites. Concerning the process mechanics, the intermetallic compound formation, defect generation, and material mixing are discussed. The joints' resulting performance is shown by detailing the essential properties such as formability, residual stresses, fatigue, hardness, and tensile strength. Additionally, several future research directions are presented at the end of this critical review
... FSP is a solid-state fabrication process that modifies the metallic materials microstructure [1][2][3] which works based on the friction stir welding (FSW) principle [4]. It is first developed by Mishra et. ...
Friction Stir Processing (FSP) is a proven technique for the fabrication of Metal Matrix Composites. It is shined in these recent years for its enormously improving capabilities of surfaces of different materials. As Carbon Nanotubes (CNTs) hold excellent mechanical, thermal, and electrical traits, they have become a boon as reinforcements to improve the properties of the materials. Reinforcing CNTs into the materials using FSP exceptionally increases the properties of different materials. This article reviews the CNT's reinforcement with metals such as Aluminum, Magnesium, Copper, and few other alloys by exploring the lat-est tendencies and techniques employed to manufacture the particulate metal matrix composites, to improve friction stir process efficiency. Moreover, notable microstructural features and mechanical properties are also discussed. The article concludes with the conclusion drawn from the literature and future work that needs consideration is also mentioned.
... As a result, an ultra-fine grained microstructure is generated in the processing zone. The extensive grain refinement (upto ~ 3.3 μm) and presence of equiaxed grains in the stir zone (SZ) of FSPed 7075-T651 Al alloy at 1 × 10 -2 s −1 and 490 °C is attributed to the dynamic recrystallization (DRX) mechanism [33]. However, a better application of the FSP technique is to exploit its ability to surface modify components, where enhanced tribological performance and surface hardness are required. ...
Aluminium metal matrix composites (AMMCs) are the fastest developing materials for
structural applications due to their high specific weight, modulus, resistance to corrosion and
wear, and high temperature strength. Carbon nanotubes (CNTs) is known as the material of the
21st century is evaluated concerning its application in structural components for their high
specific strength as well as functional materials for their exciting thermal and electrical
characteristics. The present study comprise a systematic literature review of Al/CNT
nanocomposites fabricated through a solid state friction stir processing. The literature review
is primarily focussed on dispersion and survivability of CNTs in the Al matrix because these
are the key factors in deciding the mechanical properties of the fabricated composite.
Additionally, the formability, weldability and machinability of the FSPed fabricated
composites are also summarised here. Based on the detailed literature review, following
research gaps are identified which needs a critical and more focussed attention of the scientific
community working in this research area: (i) the presence of agglomeration or clustering of
CNTs in the composite, (ii) survivability and shortening of CNTs during FSP, (iii) interfacial
reactions or the formation of reaction products (such as Al4C3) between Al matrix and CNTs,
and (iv) the unidirectional alignment of CNTs in the fabricated composite. Important
suggestions for further research in effective dispersion of CNTs with its preserved structure by
FSP are provided.
... At present, there are several methods through which reinforcements can be introduced in the metal matrix. Most of the researchers followed the method of reinforcement by creating a reservoir such as holes or grooves for preplacing the reinforcements before FSP [28][29][30]. With the modification in this method, some researchers used an aluminium sheet to cover the reservoirs to prevent the particles from being airborne during FSP [10]. ...
The present study aims to investigate the effect of reinforcement incorporation approach on the microstructure, mechanical, and tribological properties of the Al-CNT nanocomposite fabricated through friction stir processing (FSP). With the proposed multiple micro-sized channel reinforcement filling (MCRF) approach, the extensive grain refinement of ∼ 23 % is achieved as compared to the conventional single macro-sized channel reinforcement filling (SCRF) approach. The extensive grain refinement is attributed to the better consolidation obtained by the sandwiched aluminium matrix between the successive reinforcement grooves. The tensile strength of the MCRF fabricated composite is increased by ∼ 22 % at the cost of only ∼ 3% decrease in the elongation as compared to the un-reinforced processed alloy (Reference material, RM). The specific wear rate of MCRF fabricated Al-CNT composites is also reduced by ∼ 20 % as compared to RM. The improved wear performance is attributed to the formation of a carbon rich tribo layer which prevents the direct contact of composite with the counter surface. Whereas, the strengthening of Al-CNT composites is attributed to various mechanisms such as grain refinement, Orowan looping, load transfer through the interface and thermal mismatch between CNTs and Al matrix.
... The friction between the tool and workpiece causes localized heating along with plastic deformation. The rotational agitation forces the material to withstand severe plastic deformation and significant grain refinement [10][11][12][13]. A new surface formed by the FSP has three regions with different thermo-mechanical histories, which can be identified in the cross section. ...
The effects of rotational speed in range of 800-1600 rpm and traverse speed in range of 12-40 mm/min on the mechanical and microstructural properties of 2205 duplex stainless steel were studied. The temperature and strain were crucial to the microstructural evolutions in the stir and thermomechanical affected zones. The major microstructural evolution is the breaking of austenite islands and morphological change into spherical volumes named as "dynamic globularization". The hardness was maximum in the stir zone and decreased by passing through the thermomechanical and heat affected zones. A linmaear equation was developed between hardness and the ratio of ω/S. The highest hardness was obtained at 1000 RPM and 12 mm/Min. The results of tensile test showed that the ultimate tensile strength (UTS) and fracture strain are improved by FSP. UTS and fracture strain increased with increase in the rotation speed and decrease in the traverse speed.
... FSW zones[3] 2. Experimental work FSW procedure on 6005 metal alloy plates thickness of 3 mm, length of 20 cm, width of 7.5 cm as shown inFigure (3), a clamping fixing tool was used to fix the samples welded on the milling machine show in figure ( 4 ) Standard mechanical properties of 6005 AA of current and standard work are shown in ...
Friction Stir welding (FSW) is a welding method that occurs without fusion and smoothed the granules, used to improve the fine structural properties of metals. In this paper, the enhancement of mechanical properties for FSW samples at rotation speeds (1000, 1100 and 1200 rpm) with welding speed (45 mm/min) for 6005 AA is studied by using the method of FSW at the same variable rotating speed and feeding speed. In order to convert a heterogeneous nanoscale structure to a more precise and homogeneous monolithic structure. The best welding results obtained at parameter 45 mm/min are welding speed and rotational speed of 1100 rpm at FSW where efficiency reaches 96% for FSW for maximum tensile strength of mother metals. The FSW was developed as a finite element simulation of (FSW) of 6005 AA. Numerical simulations of thermal conductivity, heat and specific density were developed to find out the relationship between these factors and maximum temperature.
... FSP is a solid-state processing technique that was first developed by Mishra et al. [13] in 1999. Along with the production of super-plasticity into the materials [14], this technique is also used to produce surface composites [15][16][17][18]. FSP works on the basic principle of Friction Stir Welding [19]. ...
In this paper, Friction Stir Processing was used to process the surface of aluminum 5052. Different tool rotating speeds and tool traverse speeds were combined and were then used for the study. Micro-hardness and wear tests were performed on the surface of Al5052 after FSP and the results were then compared to the base metal without FSP. Results showed that the samples processed with FSP provided better micro-hardness values as compared to the base material. The wear test as well as the coefficient of friction was performed and showed better results than the parent material without FSP.
This study applied friction stir processing (FSP) to the TIG weldments of AA6082-T651 and AA8011-H14 with a single and double V-joint to analyze the FSP technique's impact on the TIG weldments' tensile characteristics. The single V-groove TIG (TIG SV) welded joint was more porous than the double V-groove (TIG DV) one; however, both joints exhibited a coarse-grained microstructure. When FSP was applied to the TIG weldments, the coarse grain structure (grain size 32.05 µm) was transformed into a refined grain structure (grain size 6.68 µm), thereby eradicating the defects that had been seen before FSP. Regardless of the TIG welding groove, FSP enhanced the flexural and tensile properties of the TIG welded joints. Similarly, the hardness was found to have improved due to FSP. However, when comparing the TIG SV + FSP joint properties to those of the TIG DV + FSP joints, it was observed that the TIG DV + FSP joints showed more improved properties. This behavior was correlated with the microstructural grains obtained. The maximum tensile strength of 95.3 MPa was observed for TIG DV + FSP, while the minimum tensile strength (56.1 MPa) was found in the TIG SV joint. The TIG DV welded joint showed a hardness higher by 13.44% compared to that of the TIG SV welded joint, while the TIG DV + FSP joint had a hardness higher by 21.24% than the TIG SV + FSP joint.
Conventional metal matrix composites (MMCs) with particles, whiskers, and fibers as reinforcements have been developed primarily for structural applications. Despite their long history of progress, however, MMCs exhibit sluggish performance enhancements. Low-dimensional nanomaterials, such as carbon nanotubes, graphene, boron nitride nanotubes, boron nitride nanosheets, MXene, and metal dichalcogenides, have emerged as effective nano-sized fillers for developing metal matrix nanocomposites (MMNCs) to overcome the performance limitations of conventional materials. Although various low-dimensional nanomaterial fillers have been considered as promising candidates for enhancing the multifunctional performance of MMNCs, structural properties of MMNCs filled with 1-D or 2-D nanomaterials have been a major area of research. Taking advantage of the unique properties of low-dimensional nanomaterials, multifunctional MMNCs have exhibited a remarkable trend in the development of advanced materials to meet the complex demands of emerging application areas. In this review, the current state of recent research in the field of 1-D and 2-D nanomaterial-filled MMNCs is discussed. Additionally, we have examined a vast array of fabrication processes for tailoring the microstructures and interfaces of MMNCs. Moreover, discussions on the structural and functional properties, applications, challenges, and future prospects of multifunctional MMNCs filled with low-dimensional nanomaterials have also been presented.
Equal channel angular pressing (ECAP) was applied to a biomedical TiZrNb medium entropy alloy (MEA) with an equal atomic ratio at 480 °C with 1, 2, 4, and 6 deformation passes in route C to enhance the mechanical properties and exploit the plastic deformation mechanism of the MEA. As the applied strain increased, dendritic grains first tended to merge and form equiaxed grains, which eventually elongated and formed coarse grains. Simultaneously, many straight dislocations and dislocation loops occurred and coalesced into a line during the early stages. Then, they rearranged to construct highly dense dislocation walls (HDDWs) and evolved into shear bands, maintaining the continuity of the deformation. After a 6-pass deformation, the TiZrNb MEA exhibited a yield strength of 1170 ± 21 MPa, higher than that of the as-cast sample of 830 ± 21 MPa, and a maximum hardness of 389 ± 11 HV0.2, which enhanced its wear resistance.
As the lightest metal structure material, Mg-Li alloy possesses many advantages and promising applications, but the low strength at room temperature limits its application. Multi-pass friction stir processing (MFSP) is expected to be an effective and simple method to overcome this shortcoming. In this study, the plate of LA103Z Mg-Li alloy was treated using MFSP. The mechanical properties, microstructure, and corrosion resistance of the plate before and after MFSP were compared. It was found that MFSP can effectively improve the mechanical properties of the plate, and the tensile strength and microhardness have been enhanced. Meanwhile, the plasticity of the material was also significantly improved, and the elongation increased by up to 109.2%. Furthermore, the corrosion resistance of the plate after MFSP was also increased.
An enormous amount of research has been conducted on aluminium alloys in friction stir processing (FSP), despite magnesium alloys reporting severe weight reduction when compared to aluminium alloys; a very slight amount of research has testified for FSP of magnesium alloys. Magnesium is highly reactive and susceptible to corrosion in the presence of an aggressive environment. This highly corrosive nature of magnesium limits its applications. Surface properties like crystal structure, composition, and microstructure influence the corrosion and wear properties of the material. Coating techniques and alloying techniques like laser surface modifications are performed to passivate the magnesium surface from corrosion. Coating techniques, however, have been found to be insufficient in corrosion protection due to coating defects like pores, cracks, etc, adhesion problems due to poor surface preparation of the substrate, and impurities present in the coating which provide microgalvanic cells for corrosion. The current study gives a detailed overview of different types of surface modification methods, such as physical vapour deposition, chemical vapour deposition, chemical conversion coating, and ion implantation coating techniques, and also focuses on a few alloying or surface processing methods, such as laser surface modification – namely laser surface melting, laser surface cladding, laser shot peening, laser surface alloying and FSP. FSP is a novel surface modification method derived from friction stir welding, which modifies the microstructure and composition of surface layer without changing the bulk properties to enhance corrosion resistance. FSP enhances and homogenizes the microstructure but also eliminates the breakup of the brittle-network phases and cast microstructure imperfections. Indeed, FSP can produce particle and fibre-reinforced magnesium-based surface composites. FSP empowers the manufacturing of magnesium by adding additives. The different methods of coating and surface modification are compared with FSP.
The ever-increasing demand for high performance materials in all walks of life encouraged researchers to develop composites with excellent mechanical properties. Reinforcing the Mg alloys with carbonaceous nanomaterials are progressively in focus due to their superb performance. The present research fabricated the composites by as-rolled Mg–2.97wt%Al–1.02wt%Zn–0.34wt%Mn (AZ31) alloy and graphene (GNP) through one-pass friction stir processing (FSP). For comparison with the GNP enhancement in composites, different passes FSPed AZ31 alloys were also prepared, respectively. The microstructure and mechanical properties of the investigated materials were analyzed by optical microscopy (OM), scanning electron microscopes (SEM), electron backscatter diffraction (EBSD), transmission electron microscope (TEM), and tensile tests. The average grain size of the one-pass FSPed AZ31 alloys (9.23μm) is smaller than the basal metal (BM)(47.8μm). With the increasing passes of FSP, the average grain size decreased, and basal texture became stronger, which resulted in the rising comprehensive mechanical properties of the FSPed AZ31 alloys. The GNP/AZ31 composite displayed a good ultimate tensile strength (UTS)(220MPa). The elongation (29%) of the GNP/AZ31composite increased by 202 % compared with the BM (9.6%). This is attributed to grain refinement by FSP and strengthening effects of GNP. The TEM results show that GNP was uniformly dispersed in the BM, which benefits the formation of load transfer. Thus high performance GNP/AZ31 composites are obtained.
To expand the application of wire-arc additive manufacturing (WAAM) in aluminum alloy forming components, it is vitally important to reduce the porosity, refine microstructure, and thereby improve the mechanical properties of the components. In this study, the interlayer friction stir processing (FSP) technique was employed to assist the WAAM of 4043 Al–Si alloy, and the related effects on the microstructure evolutions and mechanical properties of the fabricated builds were systematacially investigated. As compared to the conventional WAAM processing of Al–Si alloy, it was found that the introduction of interlayer FSP can effectively eliminate the pores, and both the α-Al dendrites and Si-rich eutectic network were severely broken up, leading to a remarkable enhancement in ductility and fatigue performance. The average yield strength (YS) and ultimate tensile strength (UTS) of the Al-based components produced by the combination of WAAM and interlayer FSP methods were 88 and 148 MPa, respectively. Meanwhile, the elongation (EL) of 37.5% and 28.8% can be achieved in the horizontal and vertical directions, respectively. Such anisotropy of EL was attributed to the inhomogeneous microstructure in the stir zone (SZ). Notably, the stress concentration can be effectively reduced by the elimination of porosity and Si-rich eutectic network fragmentation by the interlayer FSP, and thus the fatigue behaviour was improved with the fatigue strength and elongation increased by ∼28% and ∼108.7%, respectively. It is anticipated that this study will provide a powerful strategy and theoretical guidance for the WAAM fabrication of Al-based alloy components with high ductility and fatigue performance.
Friction stir processing (FSP) was carried out in AA6063 alloy using the tools with different pin eccentricities (0 and 0.6 mm) under different cooling rates. Results showed that the FSP using a tool with 0.6 mm pin eccentricity enhances the hardness, tensile strength, fretting wear resistance, and corrosion resistance of AA6063 alloy. Moreover, a high cooling rate using a water circulating copper block further enhances the hardness, tensile strength, fretting wear resistance, and corrosion resistance of AA6063 alloy. Pin eccentricity and increasing cooling rate reduce the peak temperature during FSP, thereby preventing grain coarsening, resulting in fine grain structure, enhancing the hardness, tensile strength, fretting wear resistance, and corrosion resistance. The XRD pattern reveals no phase changes due to FSP, but peak broadening occurred in FSP specimens.
Friction stir processing (FSP) is a new, promising technique for the grain refinement of materials. The microstructure evolution during FSP is the result of the processing parameters, dimensions of the tool, as well as the method of cooling the sample. FSP is most often carried out under natural cooling conditions in still air. However, increasingly more often additional sample cooling systems are used, which allow a significant increase in the cooling rate. Cooling substances differ in terms of their cooling mechanism, but also in terms of the requirements that must be met to make the cooling process effective and feasible. In this study, an analysis of the most commonly used methods for the rapid cooling of FSP-treated samples was performed. The characteristics of the individual solutions and used cooling agents were made; the advantages, disadvantages and limitations of the individual solutions were indicated.
Friction surfacing (FS) is a thermo-mechanical surface modification technique that can enhance the microstructure, mechanical, and tribological characteristics of a surface. The combined action of friction between the substrate and the consumable rod, as well as viscoplastic deformation in the coating and substrate materials, produces heat. FS was first restricted to the processing of soft materials such as aluminium and magnesium alloys. However, it is now gradually being introduced for hard materials and alloys also. Microstructural characteristics, tribological properties, mechanical properties and erosion-corrosion resistance are some of the processed surface qualities that can be enhanced with FS without affecting the basic material characteristics. According to the literatures, tool rotational speed, substrate travel speed, and axial force are significant process factors that affect the processed surface performance. The purpose of this paper is to examine and emphasize the different process parameter impacts on the resulting microstructural, mechanical, corrosion and tribological characteristics, as well as current challenges and future prospects in FS.
FSP (friction stir processing) technology is a modern grain refinement method that is setting new trends in surface engineering. This technology is used not only to modify the microstructure of the surface layer of engineering materials, but increasingly more often also to produce surface composites. The application potential of FSP technology lies in its simplicity and speed of processing and in the wide range of materials that can be used as reinforcement in the composite. There are a number of solutions enabling the effective and controlled introduction of the reinforcing phase into the plasticized matrix and the production of the composite microstructure in it. The most important of them are the groove and hole methods, as well as direct friction stir processing. This review article discusses the main and less frequently used methods of producing surface composites using friction stir processing, indicates the main advantages, disadvantages and application limitations of the individual solutions, in addition to potential difficulties in effective processing. This information can be helpful in choosing a solution for a specific application.
In this work, we have developed lead-free multi-layered epoxy polymer composites to effectively shield personnel and equipment against high energy γ-rays. Multi-layered shield, consisting of several layers of different materials, not only contributes to weight and cost reduction but also offers solution to inconsistent shielding performance. Compared to single layer of one type of shielding material, the probability of radiation absorption and scattering is higher in multi-layered configuration, thus enhancing shielding efficiency. However, there is a need to investigate the effect of stacking sequence and properties (dispersion of fillers, density of composites, etc.) of multi-layered materials on shielding performance. In view of this, several combinations of epoxy multi-layered composites containing micro and nano particles of both bismuth (III) oxide and tantalum (V) oxide were prepared to study the attenuation of γ-rays from 137Cs (662 keV) radioactive source. Attenuation experiments showed that the layered epoxy composites loaded with 30 wt% Bi2O3 nanoparticles alone showed around 30% γ-ray attenuation. 19-mm-thick multi-layered shield composed of two layers of n–Ta2O5/epoxy at the outer side, and two layers of n-Bi2O3/epoxy layer at the inner side were found to be as effective with almost same shielding efficiency. At around similar thickness, the epoxy composite containing n-Bi2O3/m-Bi2O3/n-Ta2O5/m-Ta2O5 layer-by-layer showed 28% attenuation, demonstrating the synergistic effect of combining micro and nano sized particles. Enhancement in attenuation on use of multi-layered structures could be attributed to the fact that epoxy composites containing different fillers of varying size will probably attenuate radiations more efficiently than those with one type of filler of a particular size. This work demonstrates that the multi-layered high-Z metal oxide-polymer composites may be as reliable as conventional lead-based materials in attenuating γ-rays.
Corrosion plays a very important role in the modern world, and there are many causes for the corrosion, in which welded joint is one of the cruiser parts, where the material undergoes corrosion. Current investigation focuses on the study of the corrosion behaviour of welded and unwelded zone in hybrid aluminium metal matrix composite. Aluminium 7075 alloy is known for its high strength and good corrosion resistance property; thus, it has a wide range of applications in building bridges, aerospace, industries, defence equipment, transport industries, railway transports and aircraft industries. An attempt is made to study the corrosion behaviour of hybrid composite aluminium alloy 7075 metal matrix prepared with fine greenish SiC of 7% along with chopped E-glass fibre and AA7075 of about 90% was produced by stir casting method with the help of graphite crucible furnace. Then the process was followed by (FSW) friction stir welding process for joining, where two hybrid MMC metals are joined with the help of a cylindrical tapered tool, with different welding parameters like transverse speed and tool spindle rotational speed of about 600, 900, 1200 rpm and feed rate is about 40, 80, 120 mm/min. Impetus gives normal force, effects of torque and the transverse force which is affecting the plate while welding. The corrosion is mainly contingent on environmental conditions, and thus the test followed by the specimen was placed in sodium chloride solution for 24 h, the flow of the election was determined between the standard electrons and sample metal piece concerning corrosion rate. The main objective is to study and evaluate the result compared with a hybrid MMC plate with aluminium 7075 base metal and weld zone. We observed that the corrosion resistance of welded composite material exhibits very high resistance to corrosion because of the uniform distribution of atoms and the compaction of atoms at the welding zone. When compared to base material welded zone exhibits a better corrosion resistance property and also changes in grain size and grain shape the effects of corrosion behaviour of a welded joint by FSW process when compared to aluminium 7075 base material.
In this paper, the metallurgical characteristics of the Friction Stir Processed (FSPed) A7075 alloy surface composites reinforced with 7.5 wt% of WC and 7.5 wt% ZrSiO4 nanoparticles were investigated. Homogenous distribution of dual reinforced particle i.e., WC and ZrSiO4 was observed during FSP, and reinforcements distribution was improved with increasing the FSP passes. Due to segregation of porosity, fine recrystallized grain-structure and dissolution of rich Al2O3 intermetallics were obtained and hence improved the processed surface properties. The mechanical properties such as micro hardness and tensile strength after 2, 4 and 6 passes were increased upto 11%, 23%, 38% and 5%, 27%, 46% compared to base metal respectively. Moreover, slurry abrasive wear was decreased with increase in FSPed passes and abrasive wheel hardness (i.e. 50, 60, 70 durometer). Hence, by increasing the slurry concentration and rotational speed (i.e. 1000, 1500, 2000 rpm) erosive wear was also decreased.
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.
In the present work, the effect of different parameters of friction stir processing (FSP) on microstructure and mechanical properties of pure copper were investigated numerically and experimentally. Three different tool rotation speed (900, 1200 and 1500 rpm) and a constant traverse speed (60 mm/min) were used as FSP parameters. To model the microstructure of stir zone (SZ) which undergos the dynamic recrystallization (DRX) and grain growth, Zener-Hollomom parameter were used to predict the grain size. In the first step the temperature distribution was formulated and solved by a commercial software COMSOL Multiphysics. An analytical model were then utilized to calculate the strain rate distribution in SZ using MATLAB. Finally, strain rate and temperature were imposed to Zener-Hollomon equation to predict the grain size. The results of modeling indicated that by increasing the rotation speed, the Z parameters decreased and subsequently the grain size increased. The predicted grain size were in a good agreement with the experimental results. The mechanical properties also improved by grain refinement.
The machining process is widely used to manufacture various machine elements for its innumerable application in manufacturing industry. The cutting fluid imparts an essential duty to the machining processes as a coolant and lubricant. With the advancement and innovations in the machining processes, the cutting fluid is under progression, and many novel cutting fluids are developed in last two decades. In recent years, the metal-oxide and non-metal-oxide particle-based nanofluids have drawn attention of the researchers due to their enhanced thermophysical and tribological properties and capabilities as efficient coolant and lubricants. This article reviews the work on potential use of the metal-oxide-based nanofluids for sustainable machining processes reported in the scientific literature over years.
A systematic study of butt friction stir welding of a recently developed Cu-containing metastable high entropy alloy (HEA) was conducted. Different zones of the weld were evaluated using mechanical testing, microstructural characterization, and differential scanning calorimetry (DSC). The nugget exhibited high tensile strength as a result of the refined equiaxed microstructure. Interestingly, the heat affected zone, which is known to be the weakest region, exhibited an excellent combination of strength and ductility as compared to the base metal. DSC was explored as a novel and quick technique to obtain enthalpy information and thus understand the TRIP effect.
In this research, the friction stir processing passes overlapping effect on AA3105/SiC is studied by evaluating the microstructural, mechanical, and tribological properties of the produced composites. The results indicated that the decrease of offset amount in different passes mediated by the more homogenous distribution of strengthening particles in the processing zone, the composite tensile strength and hardness have increased. The wear rate has decreased by 36%, compared with the sample without the strengthening phase. Also, no significant variations in the hardness, strength, and wear resistance is not seen by the friction stir processing on both sides of the sample. Although, the effect of tool shoulder induced flow is so strong that it restricts the uniform particle mixture and the access of pin-induced flow upwards the stirring region, but the offsetting decrease in the different passes reduces the tool shoulder-induce flow. The obtained highest tensile strength and the lowest wear rate of the fabricated composite equaled to 189.40 MPa and 3.6 × 10−6 gr/m, respectively.
Multi-pass friction stir processing with 100% overlap was applied to modify the as-cast 2A14 aluminum alloy plate through one to three passes. The effects of the number of FSP passes on microstructural evolution and mechanical behaviors of the stir zone (SZ) were comprehensively evaluated. The results indicated that obvious refined equiaxed grains with predominant high angle grain boundaries were formed in the SZ due to dynamic recrystallization (DRX). The grain size and tunnel defects decreased, while the second-phase particles are refined and distributed evenly as the number of passes increased. Moreover, the shear texture components of C and A1* are produced in the SZ through the DRX. As compared to as-cast alloy, the texture intensity of SZ is significantly reduced due to the formation of recrystallized grains with random orientation during FSP. Additionally, the effective improvement of strength and ductility was achieved in the two passes FSP (2P FSP) sample because of the grain refinement, fragmented particles and the elimination of casting defects. The ultimate tensile strength and elongation of 2P FSP sample reach up to 391.6 MPa and 10.8%, which are 120.9, 232.1% higher than that of the BM (177.23 MPa and 3.24%), respectively. Meanwhile, the hardness test results evidenced that 2P FSP not only enhances the microhardness, but also increases the width of SZ.
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.
In this work, the process parameters of friction stir welded dissimilar joints of aluminium alloys were analysed. The experimental investigations are carried out by the various researchers are evaluated and tabulated. Friction Stir Welding (FSW) is a solid-state metal joining process. Solid state metal joining means, the metal is not melted during the welding process and also original metal characteristics remain unchanged. Selection of material with specific properties is the key parameter in many industrial applications, especially in the aircraft and automotive industries. However, processing of such alloys with specific properties, like high strength, suffer from certain limitations in terms of cost and time of production, apart from the reduction in ductility. High strength accompanied by high ductility is possible with materials having fine and homogenous grain structures. Hence there arises a necessity to develop a processing technique that would produce a material with small grain size that satisfies the requirements of strength and ductility as well as the cost and time of production. FSP expands the innovation of friction stir welding (FSW) developed by The Welding Institute (TWI) of United Kingdom in 1991 to develop local and surface properties at selected locations. FSP is a new and unique thermo mechanical processing technique that alters the microstructural and mechanical properties of the material in a single pass to achieve maximum performance with low production cost in less time. In the present work, FSP is investigated as a potential processing technique for aluminum alloys because of various advantages it offers over other processes as mentioned above. This FSW process mostly implemented on aluminium alloys. FSW of dissimilar alloys are controlled by various process parameters, in this paper, the effect of FSW tool geometry is analyzed and tabulated. From this brief discussion, we can improve the quality of FSW process.
Microhardness Surface morphology Submerged friction stir processing Normal friction stir processing Mechanical properties a b s t r a c t The friction stir welded dissimilar aluminium alloy joints were friction stir processed under air (normal) and underwater (submerged) with room temperature conditions. The joints produced through these two distinct conditions were studied comparatively. The microstructural analysis revealed that due to the water rapid cooling system the grain sizes received were finer compared to the normal friction stir processing ones. The microstruc-tural grain refinement contributed immensely toward the joint tensile properties. The submerged friction stir processed joints were found to be more ductile compared to the normal friction stir processed ones. The positioning of the harder alloy (AA6082) on the advancing side and the soft alloy (AA8011) on the retreating side yielded better results for both normal and submerged conditions. The sampling position was also found to have an impact on the results. This was observed when the specimens cut in the beginning of the joint were studied comparatively with those cut from other locations of the joint.
High strain rate superplasticity ( i.e., superplastic behavior at strain rates over 10-2 s-1) has been observed in many metallic materials such as aluminum alloys and their matrix composites and it is associated with an ultra-fine grained structure of less than about 3 μm. Experimental investigations showed that a maximum elongation was attained at a temperature close to the partial melting temperature in many high-strain-rate superplastic materials. Recently, a new model, which was considered from the viewpoint of the accommodation mechanism by an accommodation helper such as a liquid, was proposed in which superplasticity was critically controlled by the accommodation helper both to relax the stress concentration resulting from the sliding at grain boundaries and/or interfaces and to limit the build up of internal cavitation and subsequent failure. The critical conditions of the quantity and distribution of a liquid phase for optimizing superplastic deformation was investigated. The origin of high strain rate superplasticity was considered for attaining the optimum design in microstructural control for the distribution of the accommodation helpers as well as the grain size refinement.
The high strain rate superplasticity (HSRS) for various powder metallurgy based aluminum and non-aluminum alloys has been analyzed to determine the mechanism. The mechanism of HSRS depends on the particle size of the second phase. In mechanically alloyed aluminum alloys, the grain boundary diffusion controlled grain boundary sliding dominates whereas the interface diffusion controlled sliding operates in Al/ceramic dispersed composites. A "superplastic mechanism map" for composites can be used to design PM aluminum matrix composites for HSRS. The origin of the threshold stress in such HSRS materials is discussed and the role of liquid phase in instances of incipient melting is critically analyzed.
The superplastic 7075Al alloy was tested over a range of strain rates 10[sup [minus]2] [minus]10[sup [minus]4]s[sup [minus]1] at a temperature range 430-510C using specimens machined with the rolling direction parallel and perpendicular to the tensile axis. It is shown that the mechanical properties of the alloy, including the elongations to failure, are essentially identical. Microstructural observations show that the cavities tend to form in stringers and these stringers are always oriented along the tensile axis regardless of the rolling direction. The cavities are not nucleated primarily at large Fe-rich or Si-rich particles, nor do they grow from pre-existing microvoids which may be introduced during thermomechanical processing. The cavities are nucleated preferentially at small particles or some irregularities in the grain boundary during superplastic deformation.
Friction stir welding is a relatively new technique developed by The Welding Institute (TWI) for the joining of aluminum alloys. The technique, based on friction heating at the faying surfaces of two pieces to be joined, results in a joint created by interface deformation, heat, and solid-state diffusion. In evaluating friction stir welding, critical issues (beyond a sound joint) include microstructure control and localized mechanical property variations. A serious problem with fusion welding, even when a sound weld can be made, is the complete alteration of microstructure and the attendant loss of mechanical properties. Being a solid-state process, friction stir welding has the potential to avoid significant changes in microstructure and mechanical properties. The objective of this study was to evaluate the microstructural changes effected by friction stir welding of 7075 Al.
Solid state friction-stir welding (FSW) has been demonstrated to involve dynamic recrystallization producing ultra-fine, equiaxed grain structures to facilitate superplastic deformation as the welding or joining mechanism. However, the average residual, equiaxed, grain size in the weld zone has ranged from roughly 0.5 micron to slightly more than 10 micron, and the larger weld zone grain sizes have been characterized as residual or static grain growth as a consequence of the temperatures in the weld zone (where center-line temperatures in the FSW of 6061 Al have been shown to be as high as 480C or -0.8 T(sub M) where T(sub M) is the absolute melting temperature)). In addition, the average residual weld zone grain size has been observed to increase near the top of the weld, and to decrease with distance on either side of the weld-zone centerline, an d this corresponds roughly to temperature variations within the weld zone. The residual grain size also generally decreases with decreasing FSW tool rotation speed. These observations are consistent with the general rules for recrystallization where the recrystallized grain size decreases with increasing strain (or deformation) at constant strain rate, or with increasing strain-rate, or with increasing strain rate at constant strain; especially at lower ambient temperatures, (or annealing temperatures). Since the recrystallization temperature also decreases with increasing strain rate, the FSW process is somewhat complicated because the ambient temperature, the frictional heating fraction, and the adiabatic heating fraction )proportional to the product of strain and strain-rate) will all influence both the recrystallization and growth within the FSW zone. Significantly reducing the ambient temperature of the base metal or work pieces to be welded would be expected to reduce the residual weld-zone grain size. The practical consequences of this temperature reduction would be the achievement of low temperature welding. This study compares the residual grain sizes and microstructures in 2024 Al friction-stir welded at room temperature (about 30C and low temperature (-30C).