Showing papers on "Friction stir processing published in 2020"

Friction Stir Processing of Magnesium Alloys: A Review

Abstract: Magnesium (Mg) alloys have been extensively used in various fields, such as aerospace, automobile, electronics, and biomedical industries, due to their high specific strength and stiffness, excellent vibration absorption, electromagnetic shielding effect, good machinability, and recyclability. Friction stir processing (FSP) is a severe plastic deformation technique, based on the principle of friction stir welding. In addition to introducing the basic principle and advantages of FSP, this paper reviews the studies of FSP in the modification of the cast structure, superplastic deformation behavior, preparation of fine-grained Mg alloys and Mg-based surface composites, and additive manufacturing. FSP not only refines, homogenizes, and densifies the microstructure, but also eliminates the cast microstructure defects, breaks up the brittle and network-like phases, and prepares fine-grained, ultrafine-, and nano-grained Mg alloys. Indeed, FSP significantly improves the comprehensive mechanical properties of the alloys and achieves low-temperature and/or high strain rate superplasticity. Furthermore, FSP can produce particle- and fiber-reinforced Mg-based surface composites. As a promising additive manufacturing technique of light metals, FSP enables the additive manufacturing of Mg alloys. Finally, we prospect the future research direction and application with friction stir processed Mg alloys.

Tailoring grain refinement through thickness in magnesium alloy via stationary shoulder friction stir processing and copper backing plate

Abstract: To develop ultrafine grains (UFG) in 6.35 mm thick magnesium alloy, stationary shoulder friction stir processing (SSFSP) with steel and copper backing plates was conducted. Steel backing plate produced uniform fine grains (FG) size of 4.98, 4.75, 4.12 μm in top, middle, bottom of the stir zone (SZ), respectively. In contrast, copper backing plate tailored microstructure from FG (4.1 μm) in the top to UFG (0.96 μm) in the bottom of SZ. SSFSP produced uniform and gradient microstructures, altering temperature gradient by placing steel and copper backing plates, respectively. It is worth to note that UFG microstructure achieved without usage of external cooling, owning to the copper backing plate. Most of the grains found under ~2 μm size in UFG microstructure. FG and UFG microstructures contributed to the enhancement in the ductility and strength, respectively. UFG resulted in significant improvement in hardness and tensile strength by ~80% and 24% of the base material, respectively. The intensity of strong basal texture throughout the thickness found independent of the backing plate type. Microstructure evolutions across the SZ thickness for both processing conditions are discussed using electron back scattered diffraction (EBSD).

Friction stir processing of high-entropy alloy reinforced aluminum matrix composites for mechanical properties enhancement

Abstract: Metal matrix composites have been developed to overcome the urgent demand of light-weight design High entropy alloys (HEAs) are newly emerged as a new kind of potential reinforcement for metals due to their outstanding physical and mechanical properties Here, a kind of novel Al matrix composite reinforced by Al08CoCrFeNi HEA particles was fabricated by multi-pass friction stir processing (FSP) The incorporated HEA particles were homogeneously distributed into the composites and maintained the structural integrity The average grain size of the FSPed composites decreased from 46 μm of Al matrix to 28 μm due to the particle-stimulated nucleation mechanism The hardness, yield strength and ultimate tensile strength of the FSPed composites increased by 56%, 42% and 22% than that of the FSPed Al matrix with no obvious decrease of elongation Interfacial diffusion occurred and the interfacial region is confirmed to be the Al3CoCrFeNi rather than the intermetallic phases HEA particles have great potentials in mechanical properties enhancement for conventional light-weight alloys

Titanium particulate reinforced AZ31 magnesium matrix composites with improved ductility prepared using friction stir processing

Abstract: Conventional ceramic particulate reinforcements cause a major loss in ductility of magnesium matrix composites (MMCs). Metallic particles possessing higher melting point can offer a solution to this issue. Titanium (Ti) particles (0,7,14 and 21 vol%) were reinforced into magnesium alloy AZ31 using friction stir processing (FSP) performed by a conventional sturdy vertical milling machine. The microstructure and the tensile behavior of the fabricated composites were studied in detail. The micrographs revealed a uniform distribution of Ti particles all over the stir zone irrespective of the volume content of Ti. Ti particles did not decompose or react with the matrix and its alloying elements. Ti particles established a proper interface with the matrix AZ31. Ti particles survived the severe plastic strain without breakage. The grains in the matrix were refined extremely because of dynamic recrystallization and the pinning effect of Ti particles. A large number of dislocations are found in the composite. Ti particles improved the tensile strength of the composite and helped to retain appreciable ductility.

Processing Methods and Mechanical Properties of Aluminium Matrix Composites

Abstract: Processing methods of aluminium matrix composites (AMCs) have been changing continuously considering the ease of manufacturing and the final quality of the desired composite. The most well-known processing techniques of AMCs such as stir casting, powder metallurgy, spark plasma sintering, squeeze casting, friction stir processing, liquid metal infiltration, spray codeposition, and reactive in situ techniques have elaborated here with their respective distinguishing features and mechanical properties of the fabricated composites. Moreover, this review paper contains the factors affecting the mechanical properties of AMCs as well as their clear justifications. The mechanical properties of AMCs are highly affected by the type of processing method, process parameters, and type, size, and composition of the reinforcing material. Concerning this, the mechanical properties of aluminium and its alloys are highly improved by adding a variety of reinforcing materials in a broader spectrum.

Effect of amount of TiB2 and B4C particles on tribological behavior of Al7075/B4C/TiB2 mono and hybrid surface composites produced by friction stir processing

Abstract: In this study, by friction stir processing, we fabricated several defect-free Al7075/B4C/TiB2 mono and hybrid surface composites containing various amounts of B4C and TiB2 reinforcements with high quality interfacial bonding with substrate, fine recrystallized matrix grains, and homogenous dispersion of ceramic particles through the matrix. The composite region of hybrid composite samples was more constricted compared with that of mono composite samples. All hybrid composites had more hardness and wear resistance in comparison to Al/B4C mono composite sample. Among different hybrid composites, the most optimal dispersion of ceramic particles, minimum size of B4C and TiB2 ceramic particles, the lowest friction coefficient, and the highest hardness and wear resistance belonged to the hybrid composite containing equal weight percentage of B4C and TiB2 ceramic particles (named 50%B4C-50%TiB2 hybrid composite). The hardness and wear resistance of the Al7075/B4C, Al7075/TiB2 mono composites and the 50%B4C-50%TiB2 hybrid composite were respectively enhanced by (91%, 121%, 107%) and (67%, 82%, 87%) regarding Al7075 base alloy. During wear, an unstable-simple tribolayer was formed on the surfaces of Al7075 base alloy and unreinforced FSPed samples; however, a more stable mechanically mixed tribolayer containing a mixture of oxygen, ceramic particles, and alloying elements of Al7075 base alloy and steel counterface was formed on the surface of the composite samples. The most stable tribolayer with the highest self-lubricating behavior belonged to the 50%B4C-50%TiB2 hybrid composite owing to the high amount of iron and very low amount of B4C in the tribolayer, resisting the subsurface of tribolayer to crack propagation.

Influence of Friction Stir Processing on Weld Temperature Distribution and Mechanical Properties of TIG-Welded Joint of AA6061 and AA7075

Abstract: The joining of dissimilar materials is required in many engineering and defense applications, and the conventional fusion welding often results in defective welds. The friction stir welding has minimized the welding defects, but not completed. This work focuses on the effect of friction stir processing on TIG-welded joints with filler ER 5356 to improve the mechanical properties of TIG-welded joints. In this paper, the FSP tool pin rotates on an already welded joint by TIG welding to lower the welding load and improve the weld quality by adjusting the processing parameters of friction stir processing. After analyzing the mechanical properties of TIG + FSP-welded joint, computational fluid dynamics-based numerical model was developed to predict the temperature distribution and material flow during TIG + FSP of dissimilar aluminum alloys AA6061 and AA7075 by ANSYS fluent software. The minimum compressive residual stress 18 MPa, maximum tensile strength (281.1 MPa) and hardness (107 HV) were located at the nugget zone of the TIG + FSP weldment at tool rotation speed of 1300 rpm, traverse speed of 30 mm/min and tilt angle 2°. The predicted peak values of temperature at the weld region were calculated and the maximum temperature (505 °C) and maximum heat flux (2.93 × 106 w/m2) were observed at a tool rotation of 1300 rpm.

Friction stir processing of squeeze cast A356 with surface compacted graphene nanoplatelets (GNPs) for the synthesis of metal matrix composites

Abstract: Friction stir processing (FSP) was applied to graphene nanoplatelets (GNPs) physically compacted on the surface of squeeze cast A356 alloy to incorporate GNPs within the matrix and to improve its mechanical properties. Squeeze casting resulted in finer size silicon and intermetallic compounds in cast microstructure, and subsequently FSP further refined the microstructure of squeeze cast A356 alloy, and GNP reinforced A356 alloy. The finer Si particles, intermetallics and graphene dispersed in the matrix increased the yield and ultimate tensile strength of FSP squeeze cast A356 alloy compared to the results reported in prior literature for FSP A356 alloy. Eutectic Si needles have been converted to fine spherical particles during FSP and were uniformly distributed within the nugget zone. The crystallite size of GNPs which were physically adhered to the surface of squeeze cast alloy prior to FSP decreased after FSP as a result of deformation. Thus, a combination of squeeze casting, and friction stir processing and incorporation of GNPs reinforcement in the A356 matrix is a promising route to further improve its mechanical properties.

A Review of Friction Stir Processing of Structural Metallic Materials: Process, Properties, and Methods

Abstract: Friction stir processing (FSP) has attracted much attention in the last decade and contributed significantly to the creation of functionally graded materials with both gradient structure and gradient mechanical properties. Subsurface gradient structures are formed in FSPed metallic materials due to ultrafine grained structure formation, surface modification and hardening with various reinforcing particles, fabrication of hybrid and in situ surfaces. This paper is a review of the latest achievements in FSP of non-ferrous metal alloys (aluminum, copper, titanium, and magnesium alloys). It describes the general formation mechanisms of subsurface gradient structures in metal alloys processed by FSP under various conditions. A summary of experimental data is given for the microstructure, mechanical, and tribological properties of non-ferrous metal alloys.

Effect of Friction Stir Processing on Microstructure and Mechanical Properties of TIG Welded Joint of AA6061 and AA7075

Abstract: In tungsten inert gas welding (TIG), micro-cracks, porosity, coarse grain structure and high residual stress distribution were found due to persisting thermal conditions. The TIG welded joint is processed using friction stir processing with input process parameters to avoid these defects. In present work, the experimental investigation was conducted to examine the influence of friction stir processing (FSP) on microstructure and mechanical properties of TIG welded joint of AA6061 and AA7075. Tensile test, Vickers hardness test, x-ray diffraction, microscopy and energy-dispersive x-ray test were performed for concluding the optimum set of parameters. The tensile test results shows that the hybrid TIG + FSP welded joint had higher tensile strength than TIG welded joint with filler ER4043, whereas the increment in the micro-hardness of TIG + FSP welded joint was observed. The grain size also decreases when tool pin rotates on TIG welding with different processing parameters. It was found that the maximum tensile stress, % elongation and micro-hardness at nugget zone for TIG + FSP welded joint are 255 MPa, 29.2, and 105 HV respectively. The present investigation demonstrates that the tool rotational speed and traverse speed are the dominating parameters to improve the mechanical properties of TIG welded joint.

Enhancing mechanical properties of AZ61 magnesium alloy via friction stir processing: Effect of processing parameters

Abstract: The purpose of this study was to modify the microstructure and mechanical properties of AZ61 cast magnesium alloy via solid-state friction stir processing (FSP). The effect of processing parameters on the microstructural evolution, texture and mechanical behavior was investigated. The results indicate that FSP was capable of producing fine-grained AZ61 magnesium alloy through dynamic recrystallization, and eliminating the unfavorable network-like large β-Mg17Al12 particles present along the grain boundaries in the cast magnesium alloy. With increasing ratio of rotation rate to traverse speed, the grain size and fraction of high-angle grain boundaries (HAGBs) increased. Compared with the original cast alloy, the microhardness and tensile properties of FSP specimens were significantly enhanced. The high strength and ductility of FSP specimens were achieved mainly due to the scattered distribution of crystallographic texture and the effective grain refinement along with a larger fraction of HAGBs.

Achieving simultaneously improved tensile strength and ductility of a nano-TiB2/AlSi10Mg composite produced by cold spray additive manufacturing

Abstract: The premature failure of components due to poor inter-particle bonding is the most critical issue in cold spray (CS) additive manufacturing. Herein, a hybrid strategy combining gas-atomization (involving in-situ reaction), CS, and post-friction stir processing was proposed to design a nano-TiB2/AlSi10Mg composite. Multiscale characterization in terms of X-ray diffraction and scanning and transmission electron microscopy was conducted to track microstructure evolution for better understanding the mechanisms determining mechanical performance of the produced composites. The results showed simultaneous improvement in both ultimate tensile strength (365 ± 35 MPa) and ductility (16.0 ± 1.2%), which represents a breakthrough. The strengthening and toughing mechanisms were attributed to the fine matrix grains with the significantly improved metallurgical inter-particle bonding, and the uniformly distributed TiB2 nanoparticles as reinforcement that was strongly bonded with the matrix (i.e. the formation of semi-coherent TiB2/Al interface). This study provides new guidance for hybrid additive manufacturing of metal matrix composites with high performance.

A comparative study between friction stir processing and friction stir vibration processing to develop magnesium surface nanocomposites

Abstract: Friction stir processing (FSP) can be used to improve surface composites. In this study, a modified method of FSP called friction stir vibration processing (FSVP) was applied to develop a surface composite on AZ91 magnesium alloy. In this technique, the workpiece is vibrated normal to the processing direction. The results illustrated that compared with the FSP method, the FSVP caused a better homogeneous distribution of SiC particles in the microstructure. The results also showed that matrix grains of friction stir vibration processed (FSV-processed) samples ((26.43 ± 2.00) µm) were finer than those of friction stir processed (FS-processed) specimens ((39.43 ± 2.00) µm). The results indicated that the ultimate tensile strength (UTS) of FSV-processed specimens (361.82 MPa) was higher than that of FS-processed specimens (324.97 MPa). The higher plastic strain in the material during FSVP, due to workpiece vibration, resulted in higher dynamic recrystallization, and consequently, finer grains were developed. The elongation and formability index of the FSV-processed specimen (16.88% and 6107.52 MPa%, respectively) were higher than those of the FS-processed sample (15.24% and 4952.54 MPa%, respectively). Moreover, the effects of FSVP were also found to intensify as the vibration frequency increased.

Development of AZ91/SiC surface composite by FSP: effect of vibration and process parameters on microstructure and mechanical characteristics

Abstract: A surface composite layer enhances the mechanical characteristics of a surface while retaining the properties of the base material. Friction stir processing (FSP) is a method for forming surface metal matrix composites (SMMCs) that reinforce a surface with particles. In the current study, a new method entitled friction stir vibration processing (FSVP) was applied to form SMMCs on the surface of AZ91 magnesium alloy with SiC particles as the reinforcing particles. Contrary to FSP, in FSVP, the workpiece was vibrated normal to the processing line while the tool rotated and traversed. The microstructure and mechanical properties of friction stir (FS) and friction stir vibration (FSV) processed specimens were evaluated. Additionally, the effects of vibration frequency and process parameters on different characteristics of FS and FSV processed specimens were studied. The results showed that the stir zone grains for FSV processed specimens were finer than those for FS processed specimens, and the second phase particles (SiC particles) had a more homogenous distribution in the former specimens than in the latter specimens. This was related to the effect of workpiece vibration during FSVP, which increased the material deformation and led to enhanced dynamic recrystallization and the breakdown of agglomerated SiC particles. The results indicated that the stir zone grain size decreased, and the distribution homogeneity of the SiC particles increased as vibration frequency increased. It was also observed that the stir zone grain size increased, and the mechanical properties of the processed specimens decreased as tool rotation speed increased.

Friction stir processing of Al3Ni intermetallic particulate reinforced cast aluminum matrix composites: Microstructure and tensile properties

Abstract: Friction stir processing (FSP) is used as a secondary processing technique that has been employed to enhance the microstructure and other attributes of aluminum matrix composites (AMCs). AA6061/(0–15 wt.%) Al3Ni AMCs were created using pure nickel powder, which was added to molten aluminum. The composite was then subjected to FSP. The AMC microstructures were studied prior to and after FSP using TEM, SEM, OM, and EBSD. The cast composite showed coarse grains, segregation, pores, aggression, as well as polygonal-shaped particles. FSP made the particle distribution homogeneous. Additionally, the coarse Al3Ni particles were broken down into fine particles, and the process eliminated casting defects, for example pores. The size of the grain was significantly reduced because of the severe deformation of plastic and a pinning effect induced by the particles, which were reinforced. FSP also considerably increased the density of dislocations. The resulting microstructural changes improved ductility and tensile strength.

Fabrication of Al5083 surface hybrid nanocomposite reinforced by CNTs and Al2O3 nanoparticles using friction stir processing

Abstract: In the present study, friction stir processing was adopted for surface treatment of Al5083 by incorporation of CNT and Al2O3 nanoparticles. Microstructural, mechanical and tribological properties o...

Investigation of mechanical properties and heat transfer of welded joint of AA6061 and AA7075 using TIG+FSP welding approach

Abstract: Joining of dissimilar aluminum alloys are required in many engineering applications. The fusion welding often results in defective weld like porosity, micro cracks, coarse grain structure and high residual stress. To avoid these defects the top surface of Tungsten inert gas (TIG) welded joint are processed using friction stir processing (FSP). In this work, The influences of friction stir processing on the TIG welding with filler wire ER4043 and ER5356 for dissimilar aluminum alloy AA6061 and AA7075 were carried out and investigate the residual stresses and mechanical properties of (TIG+FSP) welded joint and analyze the finite element formulation and mathematical equations of heat transfer and material flow of TIG + FSP welded joint using ANSYS fluent software by adjusting the processing parameters of FSP. The results show that the maximum compressive residual stress 64 MPa were obtained at the fusion zone (FZ) of the TIG weldment with filler ER4043, whereas minimum compressive residual stress 39 MPa was obtained at stir zone (SZ) of the TIG+FSP with filler 5356. The maximum heat flux 5.33 × 106 W/m2 and temperature 511° C were observed at tool rotation 1300 rpm with feed rate 44 mm/min. These results give the satisfactory measure of confidence in the fidelity of simulation.