Friction Stir Processing Passes Research Articles

Optimization of process parameters on the mechanical properties of AA6061/Al2O3 nanocomposites fabricated by multi-pass friction stir processing

In the present investigation, the empirical correlation was successfully developed to predict the input and output responses of the multi-pass friction stir processing (FSP)/Al2O3 nanoparticles at a 95% confidence interval (C.I). The base metal AA6061 was characterized by nanoparticles Al2O3 within the structure of the coarse dendrite. These coarse and dendrites clusters were successfully broken by multi-pass FSP (MPFSP), refined the matrix grains and produced a homogenous microstructure in the stir zone (SZ). The developed model reveals that the nanoparticles Al2O3 and FSP passes were the dominating parameters to enhance the mechanical properties of the MPFSP/Al2O3. The ultimate tensile strength (UTS) and hardness were increased with increases in nanoparticles Al2O3 and the FSP passes. The optimized value of UTS, % strain and microhardness was observed as 220.07 MPa, 13.36%, and 98.44 HV, respectively, while the optimized value of nanoparticles Al2O3 and number of FSP passes were 9.65% and 1.72, respectively.

Investigation of microstructure, crystallographic texture, and mechanical behavior of magnesium-based nanocomposite fabricated via multi-pass FSP for biomedical applications

In this work, the microstructure, crystallographic texture, hardness, and tensile behavior of AZ91/HA bio-nano composite manufactured by multi-pass friction stir processing (FSP) were investigated. With increasing the number of FSP passes, the average size of grains is reduced. The processed AZ91 and AZ91/HA nanocomposite after the third pass had the lowest grain size (4.5 and 2.6 μm, respectively). Also, the average grain size of composites was smaller than that of monolithic samples at the same pass number. The results showed that particle distribution in the AZ91/HA nanocomposite is significantly affected by the number of passes. The increment of the pass number led to a more uniform dispersion of HA nanoparticles in the matrix due to more plastic flow of materials. With increasing the pass number to three, the accumulated strain increased to 0.726 (monolithic) and 0.623 (composite) due to repeating mechanical stirring. There was a texture transition ({101‾1} to {0002}) via performing only one pass of FSP. Suppression of grain rotation by HA nanoparticles maintained the intensity of {101‾1} texture as a corrosion-resistant orientation after the third pass. With increasing the pass number of FSP, the hardness and strength of samples increased due to the grain size reduction and the more uniform dispersion of HA powder. The composite sample after the third pass exhibited the highest hardness of 117.0 HV and ultimate tensile strength of 306.6 MPa. The failure mode of processed samples was ductile. There were smaller dimples on the fracture surface of the composite samples due to their lower grain size and also the presence of HA nanoparticles. Considering the obtained results, the nanocomposite after the third pass can be a good load-bearing implant for biomedical applications.

On the Size, Shape and Spatial Distribution of Si Particles in A356 Castings After Single and Multiple Passes of Friction Stir Processing: The Effect of As-Cast Microstructures

On the Size, Shape and Spatial Distribution of Si Particles in A356 Castings After Single and Multiple Passes of Friction Stir Processing: The Effect of As-Cast Microstructures

Shape memory alloy based NiTi reinforced functionally graded material for vibration damping

Shape memory based high performance nickel-titanium alloy particles were embedded by friction stir processing in graded concentration on the surface of light weight commercially pure magnesium cast plates. The novel functionally graded material so developed was analyzed for microhardness evolution and vibration damping effect. The nickel-titanium alloy particles were filled in a 2.5 wide × 3 mm deep slot and embedded on the surface by friction stir processing. A shallower slot 2.5 wide × 1.5 mm deep was milled over the previously embedded surface in which nickel-titanium alloy powder was again filled and embedded on the surface by second pass friction stir processing. This sequence of pass created the graded variation in nickel-titanium alloy concentration. The so fabricated functionally graded material was cut out from the plate and it was hot-forged to 2/3 thickness and subsequently quenched. The microstructural examination confirmed homogeneous dispersion of nickel-titanium alloy particles and clear interface between high and low concentration regions. The microhardness confirmed a uniform graded variation in hardness. The vibration damping tests confirm considerable improvement in the damping capacity of the fabricated functionally graded material.

Effects of plasticity-induced martensitic transformation and grain refinement on the evolution of microstructure and mechanical properties of a metastable high entropy alloy

This paper describes the main results from an experimental investigation into tailoring the phase content and grain structure for high strength of a microstructurally flexible high entropy alloy (HEA), Fe42Mn28Co10Cr15Si5 (in at%), using rolling, friction stir processing (FSP), and compression. Optical microscopy, neutron diffraction, and electron backscatter diffraction were employed to characterize microstructure and texture evolution. The material upon rolling was found to have triplex structure consisting of metastable gamma austenite (γ), stable sigma (σ), and stable epsilon martensite (ε) phases. The adaptive phase stability exhibited by the selected HEA of very low stacking fault energy with strain, strain rate, and temperature was used along with grain refinement to enhance the strength. To this end, the complex structure was refined by FSP at 350 revolutions per minute (RPM) tool rotation rate, while increasing the fraction of γ and decreasing the σ and ε content. The strength was further enhanced by FSP at 150 RPM by further refinement of the grain structure and increasing the fraction of ε phase. The peak ultimate tensile strength of ~1850 MPa was achieved by double pass FSP (350 RPM followed by 150 RPM), the sequence which even more refined the microstructure and increased the fraction of σ phase. While the content of diffusion created σ phase remains constant during subsequent compression, the fraction of ε increases due to the diffusionless strain induced γ→ε phase transformation. The transformation facilitates plastic strain accommodation and rapid strain hardening, which has been attributed to the increase in highly dislocated ε phase fraction and transformation induced dynamic Hall-Petch-type barrier effect. Interestingly, a great deal of hardening ability was exhibited by the HEA even at very high strength. Roles of texture, grain size, and phase content on the transformation during compression have been rationalized and discussed in this paper.

Microstructure, mechanical properties and corrosion resistance of AZ31/GNPs composites prepared by friction stir processing

The graphene nano-platelets (GNPs) reinforced AZ31 alloy composites were fabricated by friction stir processing (FSP) with three multi-pass and high rotation speed. The AZ31/2.14 vol% GNPs and AZ31/6.43 vol% GNPs composites were designed. The fine microstructure and uniform dispersion of GNPs were observed in the AZ31/GNPs composites. The hardness and tensile properties were enhanced after three cumulative FSP passes. This was attributed to grain refinement and strengthening effects of GNPs. The corrosion resistance of the AZ31/GNPs composites was improved due grain refinement, distribution of β-Al12Mg17 phase and anti-corrosion effect of GNPs. The tensile properties and corrosion resistance of the AZ31/6.43 vol% GNPs composite increased with increasing the volume fraction of the GNPs.

Consequence of reinforced SiC particles on microstructural and mechanical properties of AA6061 surface composites by multi-pass FSP

In this work, multi-pass friction stir processing (FSP) was successfully applied to AA6061 to reinforce SiC nanoparticles producing defect-free processes. It can be inferred that Nano SiC particles were fragmented totally and uniformly distributed in sixth pass FSP. Agglomeration of SiC particles decreases with increases in the number of FSP pass. In the first pass, the SiC powder with lower formability than the base metal was concentrated inside the groove, so their flow was difficult, and most of them remained at the center of the SZ. The amount of SiC in the surface composite was further decimated after the second pass FSP cycle. At the same time, a progressive and substantial fragmentation of SiC particles ensues after the fourth and sixth passes, respectively, due to improving material mixing and dispersion. The tensile strength of AA6061 exhibited 275.7 MPa, and a percentage strain of 10.9. After implementing multi-pass FSP with nanoparticles of SiC on the AA6061, the tensile properties were enhanced simultaneously as the FSP pass increases. The tensile strength of one pass, two passes, four passes, and six passes was observed as 291.8, 307.5, 330.5, and 348 MPa, respectively, caused by strain-free fine grains during dynamic recrystallization mechanism. In contrast, Vickers’s hardness value along the centerline (stir zone) was observed as 101, 119, 125, and 134 HV with 1, 2, 4, and 6 FSP pass, respectively.

Simulation and experimental investigation of multi-walled carbon nanotubes/aluminum composite fabrication using friction stir processing

Multi-walled carbon nanotube/aluminum composites are fabricated on Al–Si cast alloy employing friction stir processing. First, the microstructure of the stir zone, as well as the effect of process parameters on the size of silicon particles, is investigated. Then, the process is numerically simulated using a thermo-mechanically coupled three-dimensional finite element method model. Material flow, as the primary reason for the dispersion of reinforcing particles, is considered in the numerical model, and proper conditions to obtain a uniform dispersion of multi-walled carbon nanotubes are determined. Scanning electron microscope analysis is carried out to consider the particle distribution in the texture of the stir zone. The results show that the particle distribution improves significantly by changing the tool rotation direction between the friction stir processing passes. The hardness test is accomplished on the cross-section of the friction stir processed specimens, and finally, the wear test is performed to compare the wear resistance of the composites with the base alloy. The results show that the wear resistance and hardness of the produced composites are considerably enhanced compared to the base alloy.

A review on microstructures and properties of graphene-reinforced aluminum matrix composites fabricated by friction stir processing

Adding reinforcement is an effective way to improve the properties of aluminum alloy. Graphene is an ideal reinforcement for the fabrication of aluminum matrix composites (AMCs) due to its excellent comprehensive performances. Friction stir processing (FSP), as a novel processing technology, is an ideal candidate for fabricating graphene-reinforced AMCs with high performances under appropriate conditions. The present paper firstly summarizes the structure-property characteristics of graphene-reinforced AMCs fabricated by FSP. Then the influences of process conditions on the structure-property evolutions of the composites are discussed. It is found that the addition of graphene leads to grain refinement and texture variation of the stir zone during FSP. Besides, mechanical properties, electrical conductivity, thermal conductivity, tribological property and corrosion resistance of the AMCs are considerably affected by the content of graphene and various microstructure evolutions induced by the added graphene. Composite of reinforcement, adding method of graphene, FSP parameters, FSP pass number and FSP path pattern are critical process conditions that determine the microstructures and properties of the AMCs. The present paper not only concludes major findings of the previous researches but also suggests future recommendations for fabrication of graphene-reinforced AMCs through FSP.

The mechanical properties of AA6082/AA1050 dissimilar joints subjected to multi-pass friction stir processing

This paper reports ‘on the influence of multi-pass friction stir processing (MFSP) on AA6082/AA1050 dissimilar joints produced by friction stir welding (FSW) technique. The produced dissimilar joints were subjected to 1pass (1P), 2pass (2P), 3pass (3P), and 4pass (4P) friction stir processing (FSP) procedure. The microstructural analysis showed the decrease in grain size with an increase in number of FSP passes. However, the tensile properties showed inverse relations with the number of FSP passes and this was linked to the dissolution of strengthening precipitates. The fractographic analysis showed the presence of dimples on all the fractured surfaces and that is an indication ductile fracture. However, the fractured surface of the 4P specimen was characterized by the presence of dimples mixed with flat structures which indicates ductility mixed with brittleness. There was no major influence of the number’ of FSP passes on the microhardness of the AA6082/AA1050 joint.

Fabrication of AA6061/Al2O3 surface composite by double pass friction stir processing and investigation on mechanical and wear properties

ABSTRACT Friction Stir Processing (FSP) is known for its ability to produce the surface composite. FSP technique has been proved as a leading and efficient method to increase mechanical, microstructural, and tribological properties of the prepared composites. In this paper, FSP was employed to fabricate the surface composite on aluminium alloy AA6061 by using Al2O3 as the reinforcement particles. FSP with a single and a double number of passes were used to compare their influence on the microstructural, microhardness, and tribological characteristics of the prepared composites. Uniform distribution of reinforcement particles in AA6061 was observed in double pass FSP as compared to FSP with a single number of passes. Double pass AA6061/Al2O3 surface composite showed an increase in microhardness by 21.5% and coefficient of friction by 63.45%.

The role of vibration and pass number on microstructure and mechanical properties of AZ91/SiC composite layer during friction stir processing

In this study, nano-sized SiC particles are added to AZ91 magnesium alloy using friction stir processing (FSP) and friction stir vibration processing (FSVP) to produce surface nano-composite layers. FSVP is a modified method of FSP in which the specimen is vibrated during FSP. The influence of FSP and FSVP pass numbers on mechanical and microstructural behaviors of the developed surfaces is investigated. It is indicated that nano-composite layers produced by FSVP have finer microstructures compared to those produced by FSP, and nano-sized particles are distributed more homogeneously. Furthermore, mechanical properties including hardness, scratch resistance, ductility, and strength of FSV processed specimens, were higher than those related to FS processed specimens. The results show a decline in the porosity content as the FSP passes are increased. Also, the compressive strength of the FSVP-ed composites is higher than those for the FSP-ed samples. It is also noticed that an increase in the vibration frequency during the FSVP process causes a more uniform dispersion of composite particles and thus, decreases particle clustering.

Development and Parametric Optimisation of Pure Magnesium Matrix Surface Composite by Friction Stir Processing

Friction stir processing (FSP) is an emerging method for improving surface properties of materials by composite fabrication. This study aims at optimizing the major FSP parameters and analysis of their real-time influence on the mechanical performance of a surface composite fabricated with Magnesium (Mg) matrix and Titanium Carbide (TiC) as reinforcement. Effects of different process parameters, tool rotational speed, plunge depth, the linear speed of the tool, cooling condition, and number of FSP passes have been examined. Using L27 array, a total of 27 combinations of these process parameters were analyzed by taking microhardness as an output response to find influential parameters by Taguchi's technique. Maximum micro-hardness was achieved when tool rpm of 600, cooling temperature of -10o C, tool feed of 15 mm/min, plunge depth of 0.35 mm, and 3 passes of FSP tool were chosen with the help of Taguchi's method. Analysis of variance indicated that cooling temperature, the tool feed, and the number of passes of the FSP tool were the most significant parameters.

Effect of Zener-Hollomon Parameter on Microstructure of Aluminum Based Nanocomposite Layers Produced by Friction Stir Processing

For more than a decade, there has been considerable interest in the fabrication of metal matrix composites by employing Friction Stir Processing (FSP). In this study a new model based on Zener-Hollomon (Z) parameter has been developed, which is believed to be the first of its kind, to accurately predict microstructural characteristics of Al-based composites Additionally, the processing window of composite fabrication determined and revealed that sound samples achieve within the range of 2.42 to 24.61 rev/mm for the ratio of rotation speed to travel speed (ω/ν). Recording the peak temperatures during processing beside the optical and Scanning Electron Microscopic (SEM) studies showed that increasing the number of FSP passes and the ratio of ω/ν have a remarkable influence on bolstering the role of nanoparticles in grain refinement. Results also indicated that the mean grain size of FSPed samples and matrix of nanocomposites decreases with an increase in the Z parameter. Finally, particular equations for various numbers of passes developed, which make a correlation between the grain size of Al-based composites and the FSP parameters via Z parameter.

Study of residual stresses in multi-pass friction stir processed surface composites

ABSTRACT Friction stir processing (FSP) has materialised as a significantly improved procedure for surface modification and fabrication. This has propelled its use in the industries of aerospace, automobile, and suchlike. Surface composites have many advantages over conventional composites and FSP is extensively used for their fabrication. In this study, we have compared and analysed the residual stresses of such friction stir fabricated surface composites with AA6063 as the base alloy and B4C nanoparticles as the reinforcement. Here, diethyl ether was used for the incorporation of B4C into the substrate of the base alloy. The residual stresses were measured using a portable stress analyser. The effect of the number of passes (one pass, two passes, three passes, and four passes) of FSP was studied. It was concluded that the specimen processed at 1000 rpm and three passes showed the best results.

Optimization of Parameters for the Friction Stir Processing and Welding of AA1050 Aluminum Alloy

Friction-Stir Processing (FSP) was applied on AA1050 Aluminum Alloy (AA) to find the highest mechanical properties among 28 combinations of the rotational and traverse speed (800-2000 rpm and 50-200 mm.min-1) and four different tool probe shapes (threaded, columnar, square and triangle). To this aim, the AA standard sheet went through a single pass of FSP. The 1600 rpm and 100 mm.min-1 with threaded tool probe was chosen as the best combination of rotational and traverse speed. Grain size at the Stirred Zone (SZ) was studied using Optical Microscopy (OM). The results showed that the SZ’s grain size was refined from 30 μm down to about 12 μm due to dynamic recrystallization during FSP. The processed sample exhibited improved hardness, yield stress, ultimate tensile strength, elongation up to 65, 80, 66, and 14%, respectively, compared to the annealed AA sample. Studying fractographic features by OM and field emission scanning electron microscope (FESEM) revealed a dominantly ductile fracture behavior.

Synthesis of radar-absorbing NiFe2O4 nanoparticles and effects of pass number on mechanical properties of AA7075/NiFe2O4 surface nanocomposites fabricated by FSP

In this paper, first, the desired NiFe2O4 nanoparticles were produced using the hydrothermal method then the AA7075/NiFe2O4 surface nanocomposite was fabricated by the friction stir processing (FSP) method. The results show that the hydrothermal method is very suitable for making NiFe2O4 nanoparticles with a fine and uniform structure that the fabricated nanoparticles have a superparamagnetic property that can be used for radar-absorbing coatings. The nanoparticles were well distributed in the base AA7075 aluminum alloy sheet in addition to the fine-grained structure achieved using FSP. The microhardness of the FSPed and surface nanocomposites were significantly improved compared to the base metal and increased with the increasing pass number of FSP. Also, the tensile properties consist of the ultimate tensile strength (UTS), formability, and toughness decrease with increasing the number of FSP passes.

Investigating the influence of single-pass and double-pass friction stir processing on mechanical and wear behaviour of AA5083/Al2O3 surface

Friction Stir Processing (FSP) has established itself as an efficient technique to manufacture surface composite. Since the development of FSP, a variety of surface composite coatings have been produced with the help of this technique. Surface composite provides an enhancement in the material’s properties by providing a coating layer of composite material on the parent material. Various FSP process parameters can affect the produced surface composite and its properties. One of the important FSP parameters includes the number of passes over the surface of a material. In this paper surface composite of AA5083/Al2O3 was produced using FSP. Single-pass and double pass FSP were employed to understand its effect on microhardness, tensile strength, microstructure coefficient of friction, and wear rate. It was observed that the double pass aided to produce the homogeneously dispersed reinforcement particles in the surface composite along with fine grain microstructure. FSP helped to enhance the microhardness from 79.5 HV in the parent material to 136.5 HV in double pass FSP. Moreover, FSP helped to increase the tribological properties after two passes. However, the ultimate tensile strength was reduced after FSP.

Applying multi-pass friction stir processing to refine the microstructure and enhance the strength, ductility and corrosion resistance of WE43 magnesium alloy

Magnesium alloys have many unique properties, mostly benefitting from the low density of magnesium. However, they are not competitive, when compared with other lightweight materials, such as aluminum alloys, particularly in ductility and corrosion resistance. There is a strong need to improve the mechanical properties and corrosion resistance of magnesium alloys. In the present research, friction stir processing (FSP) as a severe plastic deformation process was applied to the WE43 magnesium alloy. The effect of FSP up to 6 passes on the grain structure, second-phase particle distribution, mechanical properties and corrosion resistance of the alloy was investigated. It was found that a continuous network of second-phase particles was present at the grain boundaries, which was considered to be one of the main causes for the poor ductility of the alloy in the as-annealed state. By applying two passes of FSP, the grain structure was significantly refined, changing from an average grain size of 12.4 to 2.5 μm. By further FSP, the grain structure continued to refine to an average grain size of 1.4 μm after 4 passes and remained unchanged after 6 passes. However, the fragmentation and redistribution of second-phase particles continued to occur during the 4th and 6th passes of FSP. Because of these microstructural changes, the uniform strain to maximum stress and the strength of specimens gradually improved with increasing number of FSP passes. The corrosion resistance of the alloy was found to be improved by applying 6 passes of FSP, compared to that of the alloy in the initial as-annealed state, which was attributed to the fragmentation and redistribution of second-phase particles. By applying FSP, the uniformity of the protective passive layer was improved and, in the meantime, the intensity of micro-galvanic coupling leading to pitting corrosion was decreased.

Microstructural evolution and mechanical behavior of powder metallurgy based SiC/Al–Mg-Sc-Zr nanocomposite subjected to multi-pass friction stir processing

Abstract Powder metallurgy (PM) is a versatile technique to fabricate the particulate reinforced aluminum matrix composites (AMCs) by combining Al alloy powders with various types of reinforcement particles. However, the AMCs fabricated by PM generally lack ductility due to processing-related factors such as porosity, oxygen content, and undesirable microstructural features initiated by the contamination during powder preparation or sintering. In this study, the 5 wt% SiC/Al–Mg-Sc-Zr nanocomposite produced by PM was subjected to friction stir processing (FSP) to obtain the dense, uniform and refined microstructures and the attendant improved mechanical properties. The effect of FSP passes on the microstructural features and mechanical properties of as-PM nanocomposite was investigated, and the strengthening and toughening mechanism of FSPed nanocomposite was revealed. The results showed that the FSP passes with the opposite moving direction of FSP tool between the consecutive passes, largely affected the microstructure of the stir zone. Increasing FSP passes significantly reduced the microdefects and homogenized the microstructure. After 4-pass FSP, the whole stir zone consisting of the dense, uniform and refined microstructure, was obtained. This resulted in an increase in yield strength from 92 MPa in the as-PM condition to 161 MPa after 4-pass FSP, and a simultaneous nearly double enhancement in fracture strain from 0.11 to 0.29.