Prediction of mechanical and wear properties of copper surface composites fabricated using friction stir processing

Friction stir processing (FSP) has evolved as a novel solid state method to prepare surface composites. In this work, FSP technique has been successfully applied to prepare copper surface composites reinforced with variety of ceramic particles such as SiC, TiC, B₄C, WC and Al₂O₃. Empirical relationships are developed to predict the effect of FSP parameters on the properties of copper surface composites such as the area of the surface composite, microhardness and wear rate. A central composite rotatable design consisting of four factors and five levels is used to minimize the number of experiments. The factors considered are tool rotational speed, traverse speed, groove width and type of ceramic particle. The effect of those factors on the properties of copper surface composites is analyzed using the developed empirical relationships and explained in this paper taking into account the microstructural characterization of the prepared copper surface composites. B₄C reinforced composites have higher microhardness and lower wear rate.     

Role of friction stir processing parameters on microstructure and microhardness of boron carbide particulate reinforced copper surface composites

Friction stir processing (FSP) was applied to fabricate boron carbide (B₄C) particulate reinforced copper surface composites. The effect of FSP parameters such as tool rotational speed, processing speed and groove width on microstructure and microhardness was investigated. A groove was contrived on the 6 mm thick copper plates and packed with B₄C particles. FSP was carried out using five various tool rotational speeds, processing speeds and groove widths. Optical and scanning electron microscopies were employed to study the microstructure of the fabricated surface composites. The results indicated that the selected FSP parameters significantly influenced the area of surface composite, distribution of B₄C particles and microhardness of the surface composites. Higher tool rotational speed and lower processing speed produced an excellent distribution of B₄C particles and higher area of surface composite due to higher frictional heat, increased stirring and material tranportation. The B₄C particles were bonded well to the copper matrix and refined the grains of copper due to the pinning effect of B₄C particles. B₄C particles retained the original size and morphology because of its small size and minimum sharp corners in the morphology.     

Investigating effects of process parameters on microstructural and mechanical properties of Al5052/SiC metal matrix composite fabricated via friction stir processing

Friction stir processing (FSP) is a novel process for refinement of microstructure, improvement of material’s mechanical properties and production of surface layer composites. In this investigation via friction stir processing, metal matrix composite (MMC) was fabricated on surface of 5052 aluminum sheets by means of 5 μm and 50 nm SiC particles. Influence of tool rotational speed, traverse speed, number of FSP passes, shift of rotational direction between passes and particle size was studied on distribution of SiC particles in metal matrix, microstructure, microhardness and wear properties of specimens. Optimum of tool rotational and traverse speed for achieving desired powder dispersion in MMC was found. Results show that change of tool rotational direction between FSP passes, increase in number of passes and decrease of SiC particles size enhance hardness and wear properties.     

Microstructural, mechanical and wear behavior of A390/graphite and A390/Al2O3 surface composites fabricated using FSP

In the present investigation, A390/graphite and A390/Al₂O₃ surface composite (SC) layers were fabricated using friction stir processing (FSP). The effect of tool rotational and traverse speeds on the microstructural, mechanical and wear characteristics of the surface layers was studied. The results revealed that increasing the tool rotational speed increases the hardness of the composite layers. The traverse speed has less significant influence on the hardness of the composite layer than the tool rotational speed. The A390/Al₂O₃ surface composites exhibited higher hardness than the A390/graphite surface composites. The surface composites exhibited better wear resistance than the matrix alloy. The A390/Al₂O₃ surface composites exhibited lower wear rates than the A390/graphite surface composites. Increasing the tool rotational reduces the wear rate of both A390/Al₂O₃ and A390/graphite surface composites.     

Microstructure and microhardness of AA1050/TiC surface composite fabricated using friction stir processing

Friction stir processing (FSP) has been developed by several researchers to produce an upper surface modification of metallic materials. The fabrication of TiC particulate (~2? $\upmu $ m) reinforced aluminum matrix composite (AMC) using FSP is studied in this paper. The measured content of TiC powders were compacted into a groove of 0.5?mm × 5.5?mm. A single pass FSP was carried out using a tool rotational speed of 1600?rpm, processing speed of 60?mm/min and axial force of 10?kN. A tool made of HCHCr steel, oil hardened to 62 HRC, having a cylindrical profile was used in this study. The microstructure and microhardness of the fabricated AMC were analysed. Scanning Electron Microscope (SEM) micrographs revealed a uniform distribution of TiC particles which were well-bonded to the matrix alloy. The hardness of the AMC increased by 45% higher than that of the matrix alloy.     

Multipass FSP on AA6063-T6 Al: Strategy to fabricate surface composites

Surface composites were fabricated on AA6063-T6 base metal using silicon carbide (SiC) reinforcement particles by friction stir processing (FSP). Influence of multiple FSP passes was investigated on the SiC particle distribution, processed zone dimensions, and microhardness of fabricated composites. The rotational speed, traverse speed, and tool tilt were kept constant and the numbers of passes were varied at 2, 4, 6, and 8. The particle distribution in processed zone was analyzed using OM and SEM, while microhardness were evaluated by Vickers indentation test. The results reveal that with increase in FSP passes there is increase in processed zone dimensions and elimination of defects such as agglomeration of particles and void. The microhardness of reinforced region was increased uniformly with increasing passes which is attributed to homogeneous distribution of reinforcement particles. The peak microhardness value of 81.9 Hv was obtained in sample which is processed with eight numbers of FSP passes. Processed zone indicates good bonding with the substrate and grain refinement.     

Microstructures and mechanical properties of Al/Al2O3 surface nano-composite layer produced by friction stir processing

In this study, a new processing technique, friction stir processing (FSP) was attempted to incorporate nano-sized Al₂O₃ into 6082 aluminum alloy to form particulate composite surface layer. Samples were subjected to various numbers of FSP passes from one to four, with and without Al₂O₃ powder. Microstructural observations were carried out by employing optical and scanning electron microscopy (SEM) of the cross sections both parallel and perpendicular to the tool traverse direction. Mechanical properties include microhardness and wear resistance, were evaluated in detail. The results show that the increasing in number of FSP passes causes a more uniform in distribution of nano-sized alumina particles. The microhardness of the surface improves by three times as compared to that of the as-received Al alloy. A significant improvement in wear resistance in the nano-composite surfaced Al is observed as compared to the as-received Al.     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.     

Fabrication and wear characterization of an A413/Ni surface metal matrix composite fabricated via friction stir processing

In the present study, friction stir processing (FSP) was used for the incorporation of Ni particles into the surface of an A413 alloy to fabricate a surface composite. FSP parameters were the rotation speed of 2000 rpm, the traverse speed of 8 mm/min and the tilt angle of 2°. Single pass and three-pass FSP were conducted on the samples. For the evaluation of microstructures, optical microscopy and scanning electron microscope were utilized. Also, for the investigation of intermetallic formation, energy dispersive spectroscopy was used. The wear resistance of different composites was investigated at ambient and elevated temperatures. Microstructural observations revealed that the FSP led to significant breakup of acicular Si particles, elimination of α­Al dendrites and heal the casting porosity. It was found that the hardness and wear behavior of A413 cast alloy were strongly influenced by applying FSP. Also, the in situ formation of Al₃Ni particles during FSP was a critical factor controlling the wear mechanism. Sliding wear tests revealed that the increase in the number of passes created a homogeneous distribution of Al₃Ni intermetallic particles and thereby resulting in a significant improvement in wear resistance at both room and high temperatures.     

Effect of sliding distance on the wear and friction behavior of as cast and heat-treated Al–SiCp composites

The present investigation aims to evaluate the effect of sliding distance on the wear and friction behavior of as cast and heat-treated Al–SiCp composites using pin-on-disc wear testing machine, giving emphasis on the parameters such as wear rate and coefficient of friction as a function of sliding distance (0–5000 m) at different applied pressures of 0.2, 0.6, 1.0 and 1.4 MPa, and at a fixed sliding speed of 3.35 m/s. Characterizing the alloy and composites in terms of microstructure, X-ray diffraction analysis, microhardness and wear surface analysis. The results revealed that the heat-treated composite exhibited superior wear properties than the base alloy, while the coefficient of friction followed an opposite trend. Moreover, the wear rate of the composite is noted to be invariant to the sliding distance and increased with applied pressures. Microstructure of composite shows fairly uniform distribution of SiC particles in the metallic matrix. The hardness value of heat-treated composite increased 20–30% by addition of SiC particles to the alloy, intermetallic phases like Al₂Mg₃ and Al₂CuMg, etc., were obtained from X-ray analysis. The wear mechanism of the investigated materials was studied through worn surfaces examination of the developed wear tracks.     

Optimization of process parameters for friction stir processing (FSP) of Al–TiC in situ composite

Segregation of in situ formed particles at the grain boundaries is a major drawback of in situ composites. In this study, it has been demonstrated that friction stir processing (FSP) can be used as an effective tool to homogenize the particle distribution in Al based in situ composites and FSP processing parameters were optimized for this purpose. An Al-5 wt% TiC composite was processed in situ using K₂TiF₆ and graphite in Al melt and subjected to FSP. Processing parameters for FSP were optimized to get a defect free stir zone and homogenize the particle distribution. It was found that a rotation speed > 800 rpm is needed. A rotation speed of 1000 rpm and a traverse speed of 60 mm/min were found to be an optimum combination. The grain size was also refined in addition to homogenization of the as-cast microstructure. This resulted in significant improvement in the mechanical properties of the processed composite.     

On effect of FSP on microstructural and mechanical characteristics of A390 hypereutectic Al–Si alloy

Abstract

In the present article, the effect of friction stir processing (FSP) on the microstructural and mechanical characteristics of A390 hypereutectic Al–Si alloy was studied. The effect of tool rotational speed ω, traverse speed υ and the number of passes on such characteristics was investigated. The results showed that FSP significantly improved the microstructural characteristics of A390 Al alloy by reducing the structural defects found in the as cast alloy such as porosity and the size of α-Al primary grains as well as the size of the primary Si particles. The size of Si particulates was found to be reduced by reducing the tool rotational speed, increasing tool traverse speed and increasing the number of FSP passes.     

Effect of rotational speed and probe profile on microstructure and hardness of AZ31/Al2O3 nanocomposites fabricated by friction stir processing

Friction stir processing (FSP) was used to fabricate AZ31/Al₂O₃ nanocomposites for surface applications. The effects of probe profile, rotational speed and the number of FSP passes on nanoparticle distribution and matrix microstructure were studied. The grain refinement of matrix and improved distribution of nanoparticles were obtained after each FSP pass. By increasing the rotational speed, as a result of greater heat input, grain size of the base alloy increased and simultaneously more shattering effect of rotation, cause a better nanoparticle distribution. The average grain size of matrix of the composites was in the range of 1–5 μm and the microhardness of them was 85–92 Hv.     

Friction stir processing of Al6061-SiC-graphite hybrid surface composites

Friction stir processing (FSP) of Al6061-SiC-Graphite hybrid composites is studied in detail via force analysis, spectroscopic, microstructural and indentation studies. Effect of various tool rotational speeds was assessed, and the axial force variation was monitored. The presence of graphite as a reinforcement influences the axial force fluctuations due to its flaky nature and high thermal conductivity. Variation in microstructure at different tool rotational speed is studied using scanning electron microscope. The tool rotational speed has a significant influence on the area of FSP zone, fragmentation and depth of penetration of particles, dispersion of agglomerates and grain refinement of the matrix material. Spectroscopic characterization of the processed samples was done using Raman analysis and X-Ray diffraction studies. A noticeable change in intensity and shift in the respective Raman peak positions were observed, indicating residual stresses and various disorders in the crystal structure of the reinforced particles. Influence of tool rotational speed and existence of SiC and Graphite particles on the mechanical properties were further evaluated using nano indentation testing. The hybrid composite shows the combination of best and uniform mechanical properties at an optimum set of processing parameters.     

Investigations on the effect of friction stir processing on Cu-BN surface composites

The main aim of this investigation focuses on fabrication of copper surface composites through friction stir processing (FSP) reinforced with boron nitride (BN) particles of varying volume fractions (5%, 10%, and 15%). Surface composites developed through single pass FSP were characterized for its microstructural, mechanical and tribological properties. Microstructural characterization indicated that developed surface composites were of good quality with reduced grain size and the SEM characterization confirmed good bonding between copper matrix and BN with uniform dispersion. Micro hardness survey of the developed surface composites showcased minimal deviation in the stir zone with increased trend in respect to the volume fraction of BN. The ultimate tensile strength, yield strength and percent elongation of FSPed composites was found to have reduced when compared with that of pure copper. BN dispersion in surface composite was effective in reducing the ductility and so maximum volume percent (15%) of BN dispersed composite prompt to have higher strength. The wear rate and friction coefficient of the developed surface composite was found decreasing with respect to increase in the dispersion of BN. Amongst the FSPed copper surface composite, specimen with 15?vol% of BN has shown the least wear rate with low coefficient of friction.     

Tribological and microstructural evaluation of friction stir processed Al2024 alloy

In this study, a new processing technique, friction stir processing (FSP) was applied to Al2024-T4 as a means to enhance the near-surface material properties. Samples were subjected to FSP using a constant tool rotating rate of 800 rpm and travel speed of 25 mm/min with a tool tilt angle of 3°. Microstructural evolution and tribological behavior of friction stir processed (FSP) Al2024-T4 were investigated. Microstructural characteristics of the samples were investigated by optical microscopy (OM) and scanning electron microscopy (SEM). Evaluations of mechanical properties include micro-hardness and wear resistance. Dry sliding wear tests were applied using a reciprocating wear test. The results showed that FSP was beneficial concerning improvement of hardness and wear resistance. FSP reduced friction coefficient by approximately 30% and wear rate by an order of magnitude.     

Influence of machine parameters on material flow behavior during channeling in modified friction stir channeling

Material flows during friction stir processes are very complex and not fully understood. Although the most literature reviews are presenting for material flow path, but Modified Friction Stir Channeling (MFSC) is a novel process based on Friction Stir Processing (FSP), which is being utilized to produce internal channel in Monolithic plates. A new flow pattern, in this study, is proposed to investigate material flow path and channel formation mechanism. The validity of this model is demonstrated by observing the cross-section and created keyhole using stop-action technique. The main difference between Friction Stir Channeling (FSC) and MFSC is the tilt angle. The effect of tilt angle and process parameters such as rotational speed and traverse speed on material flow path is studied. The results indicate that the tilt angle is an effective factor on forging of material behind of pin in the Advancing Side (AS) and also in the upper portion of channel roof imperfections. The rotational speed is an effective parameter on extruded material around the tool pin body and the extracted material in front of tool pin, because of the changing in the slip–stick condition and generated heat by tool. Traverse speed was an effective parameter on forging action of material and to keep material nearby tool pin in the behind of pin.     

Distribution of reinforcement particles in surface composite fabrication via friction stir processing: Suitable strategy

Fabrication of metal matrix surface composites (SCs) is an emerging trend of friction stir processing applications. Key factors affecting the properties of SCs are process parameters, tool geometry, tool dimensions and reinforcement strategies. In this research, effects of different reinforcement strategies and varying tool offset positions on dispersion of reinforcement particles in the base matrix are investigated. The experiments were performed in two phases using AA6063 as base metal at constant process parameters of 1120?rpm rotational speed, 40?mm/min traverse speed and 2.5° tilt angle. In the first phase, effect of six different reinforcement strategies on the reinforcement particles distribution and defect formation was studied. It was found that groove method with tool offset in retreating side (RS) exhibited better homogeneity in reinforcement distribution out of the six reinforcement strategies considered. In the second phase, effect of variation of tool offset in RS was investigated. Results from second phase of experimentation reflected that the best dispersion of reinforcement powder with larger stir zone area was found with 1.5?mm tool offset which is numerically half of the tool pin radius. The results were supported by macro and microstructural images obtained from the optical microscope and scanning electron microscope.     

Strategical parametric investigation on manufacturing of Al–Mg–Zn–Cu alloy surface composites using FSP

Friction stir processing (FSP) is a unique approach being presently researched for composite fabrication. In the present investigation, Al-B₄C surface composite was fabricated through FSP by incorporating B₄C powder particles into Al–Mg–Zn–Cu alloy (AA 7075) matrix. The influence of varying powder particle reinforcement strategies on the microstructure, powder distribution, microhardness, and wear resistance of the surface composite is reported. In addition, AA 6061/B₄C composites were prepared using the same parameter set and the powder distribution in the composite was compared to that in the AA 7075/B₄C composite. More homogeneous dispersion of B₄C powder was observed in AA 6061 as compared to AA 7075 substrate. Among the prepared AA 7075/B₄C composites, the best B₄C powder distribution was detected in samples processed using fine powder and incorporating the change in stirring direction between passes. The hardness and wear resistance of the prepared composites were almost doubled attributing to several strengthening mechanisms and B₄C powder distribution in the AA 7075 matrix.     

Studies on Machining Parameters While Milling Particle Reinforced Hybrid (Al6061/Al2O3/Gr) MMC

In this article, response surface methodology has been used for finding the optimal machining parameters values for cutting force, surface roughness, and tool wear while milling aluminum hybrid composites. In order to perform the experiment, various machining parameters such as feed, cutting speed, depth of cut, and weight (wt) fraction of alumina (Al₂O₃) were planned based on face-centered, central composite design. Stir casting method is used to fabricate the composites with various wt fractions (5%, 10%, and 15%) of Al₂O₃. The multiple regression analysis is used to develop mathematical models, and the models are tested using analysis of variance (ANOVA). Evaluation on the effects and interactions of the machining parameters on the cutting force, surface roughness, and tool wear was carried out using ANOVA. The developed models were used for multiple-response optimization by desirability function approach to determine the optimum machining parameters. The optimum machining parameters obtained from the experimental results showed that lower cutting force, surface roughness, and tool wear can be obtained by employing the combination of higher cutting speed, low feed, lower depth of cut, and higher wt fraction of alumina when face milling hybrid composites using polycrystalline diamond insert.