Homogeneous Distribution Of Reinforcement Research Articles

Development and Characterization of AA2024/SiC/Gr/Fly ash Hybrid Composite

The use of hybrid composites now a days has been very attractive due to their light weight, low cost along with high strength to weight ratio. Lot of research is going on to develop the newer composites with improved mechanical, tribological and thermal properties. From the last two decades, Aluminium alloys have gained lot of attention owing to their practical usage and the ease of processing. Aluminium matrix composites are most versatile materials which has applications in advanced structure, aviation, marine and defence application due to their excellent properties. It is a known fact that stir casting is one of the economical method of fabrication of the metal matrix composite, moreover it is also easy to fabricate the composites by stir casting rather than other processes of fabrication. But, the quality of metal matrix composites being cast through stir casting route are highly dependent on the process parameters and achieving the homogenous distribution of reinforcement is a big challenge. In the present investigation, AA2024/SiC/Gr/flyash hybrid composites were fabricated with the stir casting technique (having reinforcement weight composition of SiC 10%, Graphite 5%, and fly ash 5%). The morphological characteristics of the developed Metal matrix composite (MMC) have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM). The uniform distribution of the reinforcement particles clearly depicts the development of homogeneous composite.

Role of homogeneous distribution of SiC reinforcement on the characteristics of stir casted Al–SiC composites

Stir casting process is very popular for the fabrication of particle reinforced metal matrix composites. However, achieving a homogenous distribution of the reinforcement particles is very challenging, which directly affect the final mechanical performances. In this research, a detailed investigation was conducted to obtain a superior synthesis of Al–SiC composite materials and to detect the effect of SiC particles distribution on the mechanical characteristic of the stir casted Al matrix composites using glycerol–water based model. The glycerol–water based model study displays the impacts of viscosity of Al melt (1.04–1.24 mPa.s), impeller position (10–50%), stirring speed (100–300 rpm) and blade angle (0–90°) on the vortex height, dispersion time, settling time and clustering of particles. The results of the experiments using glycerol–water based model, 45° blade angles, impeller position of 40% from the base, stirring speed of 250 rpm showed the best uniform distribution of reinforcement particles. Confirmation experiments were carried out by fabricating Al–SiC PRMMC based on three different viscosities (1.04, 1.13, and 1.24 mPa.s) of Al melt and considering other parameters as constant. Fabricated Al–SiC samples were analysed by Scanning Electron Microscope (SEM) and mechanical testing such as tensile, hardness and wear tests. Based on the confirmation results, the viscosity of 1.13 mPa.s for Al melt (at 750 °C) resulted in uniform distribution of SiC particles, which enhanced the tensile strength by 4%, wear resistance by 21%, and led to a uniform hardness value of 47 VHN throughout the composites.

Flyash and carbon fibers reinforced aluminum-based matrix composite for structural applications

Aluminum alloy and its composite showed excellent physical and mechanical properties. But still, there is a scope in improving the mechanical properties of the composite for the structural, automobile, and aerospace industry. The composites have been prepared to reach the needs of the industry. In this present work, micro-fillers such as fly ash, and carbon fiber reinforcements were added to the base AA7076 matrix and fabricated the composite using a motorized stir casting technique. AA7076/fly ash and AA7076/carbon fiber composites were prepared by varying wt.% percent of fly ash and carbon fiber reinforcements (0.5, 0.75, 1, and 1.25 wt.%) and results were compared. The SEM micrographs revealed the homogeneous distribution of fly ash and carbon fiber reinforcements along the grain boundaries of the AA7076 matrix material. The composites with 1 wt.% of micro-fillers showed superior hardness and tensile strength as compared to other reinforcement composite and base matrix. The experimental test results revealed that the addition of fly ash and carbon fiber reinforcements improved the mechanical properties of the AA7076/fly ash and AA7076/carbon fiber composites as compared to the AA7076 matrix material. Among them, the comparative study revealed that the AA7076/carbon fiber composite has showed homogeneous distribution of reinforcements and improved mechanical properties.

Investigation of mechanical properties and biocorrosion behavior of in situ and ex situ Mg composite for orthopedic implants.

In the present study, the biocorrosion and mechanical properties of in situ and ex situ ZK60 matrix composites were investigated. For this purpose, ex situ composite samples containing 10 and 20vol% SiC particles were prepared by stir casting method, while the in situ composite samples were produced by precipitation hardening at 175°C and 225°C. Microstructural examinations confirmed the homogeneous distribution of reinforcements and precipitations for ex situ and in situ composites, respectively. Moreover, the ex situ composites had higher hardness than the in situ composites due to the presence of ceramic particles. The samples were subjected to potentiodynamic polarization and electrochemical impedance spectroscopy in the SBF solution. The results showed that ex situ composites had a higher corrosion rate than in situ composites. The results of the MTT assay displayed that all samples had acceptable biocompatibility. Additionally, SEM micrographs obtained after immersion of both composites in the SBF solution for 7 and 28days showed the formation of the hydroxyapatite layer on the surface of the samples. Both composites showed almost excellent wear resistance, and SEM micrographs approved that abrasive wear and adhesive wear were the dominant mechanisms for ex situ and in situ composites, respectively.

Fabrication and Characterization of hybrid aluminium-fly ash-graphite composite

In the present paper, an aluminium metal composite with fly ash and graphite as the reinforcement were prepared using the stir casting route. The effects of reinforcements on the hardness of the Al 6061 were evaluated using a Brinell hardness tester and optical micrographs and XRD analysis was done to inspect the distribution of the reinforcements in the Al 6061 matrix. It was observed that the introduction of reinforcements in the Al matrix greatly influenced the surface hardness. There was about 32 % improvement in the hardness value. Optical micrographs also indicated the homogeneous distribution of reinforcements in the aluminium matrix.

Mechanical and tribological characterization of industrial wastes reinforced aluminum alloy composites fabricated via friction stir processing

Abstract The fabrication of particulate reinforced metal matrix composites via melt based processes poses issues like aggregation, wettability and formation of detrimental phases which may severely affect their performance. Recently developed solid-state process i.e., friction stir processing (FSP), is an efficient fabrication technique to counter the limitations of melt based processes. However, the incorporation of industrial waste in the metal matrix by using friction stir processing is rarely reported. Thus, the present investigation was carried out to reinforce the particulate type industrial waste in cast A356 alloy by friction stir processing. The performance of the fabricated composites as well as the as-cast A356 alloy was assessed through mechanical and tribological characterization. It was observed that FSP resulted in the eradication of porosity, fragmentation of α-Al dendrites, breakage and redistribution of Si particles, and grain refinement. A fair homogeneous distribution of reinforcement was observed in stir zone (SZ) with negligible aggregation of particulate reinforcement. The particle/matrix interface was free from any detrimental phase. The improvement in strength, ductility, and wear resistance was observed as compared to as-cast A356 alloy which was attributed to the microstructural changes that occurred during FSP, and the efficient reinforcement of particles via FSP.

Boron Carbide (B4C) Reinforced Aluminum Matrix Composites (AMCs)

Aluminum matrix composites (AMCs) demonstrating a good combination of properties that are hard to acquire by a monolithic aluminum material. Since the last few decades, investigators have shown their keen interest to advance these materials for complex applications. Homogeneous reinforcement distribution, defect-free microstructure, and improved resultant properties depends on the fabrication method along with matrix and reinforcement materials and size. Two-step melt stirring technique and K2TiF6 flux enhanced the wettability and improve the particle distribution of boron carbide (B4C) in AMCs. The mechanical properties of the AMCs were enriched by either extrusion process or thermal treatment. Hybrid composites exhibited better characteristics than mono composites. Surface composites manufactured by incorporation of reinforcement in the surface layer; offer good surface properties without losing toughness and ductility. The B4C-Al interfacial reactions produce different precipitates in AMCs and damaged the composite's age-hardening ability. B4C reinforced friction stir processed surface composites exhibits refined structure and better properties compared to the aluminum matrix. The strength, hardness, and wear resistance of AMCs increased with rising fraction and reducing the size of B4C up to a certain level. Wear rate increases with rising applied load, sliding time and speed. A review of effect of B4C reinforcement on different properties of mono and hybrid AMCs with summarized results attained and concluded by different investigators is presented in this paper to help researchers in the field. At the end of this paper a position given to conclusions and future directions.

Microstructural, Tribological and Mechanical Properties Evolution of ZrSiO4/A4047 Surface Composite Fabricated through Friction Stir Processing

In this study, zircon sand (ZrSiO4)-reinforced aluminum surface composite up to 15 vol % of microparticles with an average diameter of 3 µm was prepared through multi-pass FSP. The microstructural, mechanical and tribological characterizations of the friction stir-processed ZrSiO4/A4047 surface composite were evaluated. The effects of FSP passes (2, 4 and 6) were evaluated, and it suggests that the surface composite after 6-pass reveals better homogeneous distribution of reinforcement (ZrSiO4) particle in the matrix. The tensile test showed 16, 24 and 44% with increase in FSP passes, respectively, compared to the base metal. Similarly, the microhardness of the surface composite produced through 6-pass FSP was increased to 112 HV while that produced through base metal increased to 74 HV. Also, it was observed that erosion–corrosion resistance and abrasion wear performance were significantly improved with increase in FSP passes.

Microstructure and Tribological Performance of Alumina–Aluminum Matrix Composites Manufactured by Enhanced Stir Casting Method

Al–Zn–Mg–Cu matrix composites reinforced with (0–20 wt %) Al2O3 particles have been manufactured by enhanced stir casting technique. Microstructural characterization of cast composites by optical, field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDS) and X-ray diffraction (XRD) reveals homogeneous distribution of reinforcements in Al-alloy matrix with MgZn2 plus Al2CuMg intermetallics. With increasing particle content, hardness of composite rises considerably in spite of marginal rise in porosity. Tribological performance under two-body abrasion has been studied considering central composite design (CCD) apart from identification of mechanisms of wear via characterizations of abraded surfaces and debris. Composites exhibit significantly reduced wear rate and coefficient of friction (COF) irrespective of test conditions, since mechanisms of abrasion are observed to change from microplowing and microcutting in unreinforced alloy to mainly delamination with limited microplowing in composites. Effects of four independent factors (reinforcement content, load, abrasive grit size, and sliding distance) on wear behavior have been evaluated using response surface-based analysis of variance (ANOVA) technique. Dominant factors on both wear rate and COF are identified as reinforcement content followed by grit size and load. Combined optimization of wear rate and COF employing multiresponse optimization technique with desirability approach as well as regression models of individual responses have been developed, and their adequacies are validated by confirmatory tests. The developed mathematical models provide further insight on the complex interactions among wear performances of the selected materials and variables of abrasive system. The optimum amount of reinforcement is identified at around 15 wt % for achieving the lowest values of both wear rate and COF.

Effect of ZrO2 content on properties of Cu-ZrO2 nanocomposites synthesized by optimized high energy ball milling

In this paper, copper matrix nanocomposites reinforced by 5, 10 and 15 wt% ZrO2 particles were produced using high energy ball milling technique with different milling time. The optimum milling time is predicted analytically and validated experimentally. The effect of ZrO2 content on the morphology, microstructure, microhardness, compressive, electrical and wear properties of Cu-ZrO2 nanocomposites has been investigated. The results revealed that the optimum milling time to produce Cu-ZrO2 nanocomposite with homogenous distribution of reinforcement is 15 h. The compressive strength, the microhardness and wear rate of the Cu-15%ZrO2 nanocomposites are improved by 58.2%, 288% and 19.3%, respectively, compared to pure copper. However, density and electrical conductivity are negatively affected by increasing ZrO2 content. The improvement in the mechanical and wear properties comes from the large reduction of the crystallite size by increasing ZrO2, reaching 32.5, 15.2 and 11.1 nm for samples containing, 5, 10 and 15 wt% ZrO2. Moreover, the reduction in the particle size due to mechanical milling plays a critical role in the improvement of these properties.

Microstructure, Friction and Wear of Aluminum Matrix Composites

MMCs are made by dispersing a reinforcing material into a metal matrix. They are prepared by casting, although several technical challenges exist with casting technology. Achieving a homogeneous distribution of reinforcement within the matrix is one such challenge, and this affects directly on the properties and quality of composite. The aluminum alloy composite materials consist of high strength, high stiffness, more thermal stability, more corrosion and wear resistance, and more fatigue life. Aluminum alloy materials found to be the best alternative with its unique capacity of designing the materials to give required properties. In this work a composite is developed by adding silicon carbide in Aluminum metal matrix by mass ratio 5%, 10% and 15%. Mechanical tests such as hardness test and microstructure test are conducted.

Mechanical and tribological properties of LM13/TiO2/MoS2 hybrid metal matrix composite synthesized by stir casting

ABSTRACTThis paper involves the fabrication of LM13/TiO2 (12 wt%)/MoS2 (3 wt%) hybrid metal matrix composite and unreinforced alloy using liquid metallurgy route and evaluation of mechanical properties and adhesive wear characteristics. Microstructural investigation revealed homogeneous distribution of reinforcements in matrix. Hardness and tensile properties revealed that the composite had attained an improvement of 16.5 and 35%, respectively, over alloy. Wear characteristics were analyzed using pin-on-disk tribometer by varying load (10–40 N), sliding velocity (1–4 m/s), and sliding distance (500–2000 m). Statistical analysis was performed using response surface methodology to obtain the optimum wear process parameters for achieving maximum wear resistance. Results revealed that, with increasing load and sliding velocity, an increment in wear rate was observed for both alloy and composite, while a decline was observed with increasing sliding distance for composite and vice versa for alloy. Worn surface analysis revealed that load plays a prominent role in deciding wear rate, followed by sliding velocity. Sliding distance had less effect on wear rate of composite while it had significance on alloy. This hybrid composite can replace the conventional material used in automotive applications involving tribological importance.

Joining and fabrication of metal matrix composites by friction stir welding/processing

Herein, friction stir welding (FSW) of metal matrix composites (MMCs) with different combinations of the reinforcement and the metal matrix is highlighted with a brief introduction into recent efforts that have been used to fabricate MMCs by FSW. As a solid state joining technique, FSW consumes significantly lower energy than conventional fusion welding processes. In addition to properly selecting the process parameters, the mechanical properties of the FSW joints of MMCs are closely related with the refinement and homogeneous distribution of reinforcements in the stir zone. The fatigue and fracture properties of MMCs may be enhanced or aggravated by FSW, depending on the combination of the reinforcement and the metal matrix. For FSW of MMCs, the selection of the tool material can also be a critical issue; the presence of hard reinforcements may increase the rate of tool wear. Macro-and microstructural phenomena for MMCs during FSW depend on the material flow due to plasticization and the behavior of the reinforcements. Even though FSW are generally expected to induce a homogeneous distribution of reinforcements in the stir zone (SZ), it can be difficult to obtain a homogeneous distribution of reinforcements in the SZ depending on the combination of the reinforcement and the metal matrix. The existence of reinforcements naturally affects the microstructure of the joint and can even induce the formation of intermetallics/complex phases in the joint. This review provides a general understanding of the joining or in-situ fabrication of MMCs using solid-state friction stirring.

Reactive friction-stir processing of an Al-Mg alloy with introducing multi-walled carbon nano-tubes (MW-CNTs): Microstructural characteristics and mechanical properties

In this research, a fine-grained aluminum matrix hybrid nanocomposite was fabricated by reactive friction-stir processing (FSP) of an Al-Mg alloy containing about 2.5vol% of embedded multi-walled carbon nano-tubes (MW-CNTs). It was shown that a homogenous distribution of reinforcement is attained throughout the metal matrix by applying parameters involving w=1400rpm and v=50mm/min during 5 cumulative FSP passes, where a maximum temperature of 510°C is reached during processing. The survivability of these tangled MW-CNTs is diminished by the thermo-mechanical conditions imposed during FSP. Transmission electron microscopy analysis reveals that in situ solid-state chemical reactions occur at high temperature between the Al-Mg alloy and the nano-tubes during the severe plastic deformation. Consequently, aluminum carbide (Al4C3) and fullerene (C60) nano-phases with an average size of <50nm are formed. The structure of precipitates and grains are also changed due to the applied severe plastic deformation, which ultimately improves the indentation and tensile properties of the processed alloy. The formation of a fine-grained structure (with average size of ~1.5μm) and in situ nucleated phases formed from remnant CNT fragments is accompanied by a significant increase in the yield strength (~140.7MPa) and Vickers hardness (~95.6HV). By employing experimental and theoretical models, a relationship between the microstructure and mechanical properties is established. The contributions of different mechanisms to strengthening are explained using prevailing theories based on the role of grain refinement and direct strengthening by Orowan looping, which were found to be more effective compared to the load bearing strength contribution.

Fabrication and Mechanical Properties of Extruded Al-SiC Nanocomposites

This work aims to investigate the effect of SiC addition on structural, microstructural and mechanical properties of developed Al-Sic nanocomposites. Al metal matrix composites reinforced by nanosized SiC particles were fabricated using high energy ball milling and microwave sintering process followed by hot extrusion. The XRD analysis indicated that the dominant components were Al and SiC. SEM/EDX micrographs showed homogenous distribution of SiC nanoparticles in Al matrix. Mechanical characterizations revealed that the addition of nanosize SiC particulates to a simultaneous increase in microhardnes, yield strength, ultimate compressive/tensile strength and reduction in ductility of the matrix. This improvement in mechanical properties can be attributed to the homogeneous distribution of reinforcement (SiC particles) and dispersion strengthening mechanism.

Synthesis and characterisation of advanced ball-milled Al-Al2O3 nanocomposites for selective laser melting

Selective laser melting (SLM) offers significant potential for the manufacture of the advanced complex-shaped aluminium matrix composites (AMCs) used in the aerospace and automotive domains. Previous studies have indicated that advanced composite powders suitable for SLM include spherical powders with homogeneous reinforcement distribution, a particle size of <100μm and good flowability (Carr index<15%); however, the production of such composite powders continues to be a challenge. Due to the intensive impacts of grinding balls, the high-energy ball-milling (HEBM) process has been employed to refine Al particles and disperse the nano Al2O3 reinforcements in the Al matrix to improve their mechanical properties. Notwithstanding, the specific characteristics of ball-milled powders for SLM and the effect of milling and pause duration on the fabrication of composite powders have not previously been investigated. The aim of this study was to synthesise Al-4vol.% Al2O3 nano-composite powders using HEBM with two different types of milling and pause combinations. The characteristics of the powders subjected to up to 20h of milling were investigated. The short milling (10min) and long pause (15min) combination provided a higher yield (66%) and narrower particle size distribution range than long milling (15min) and a short pause (5min). The nano Al2O3 reinforcements were observed to be dispersed uniformly after 20h of milling, and the measured Carr index of 13.2% indicated that the ball-milled powder offered good flowability. Vickers micro-hardness tests indicated that HEBM significantly improved the mechanical properties of the ball-milled powders.

Microstructure and Mechanical Properties of Mg/2 wt.%SiCp Nanocomposite Fabricated by ARB Process

Magnesium matrix nanocomposites (MMNC, the same below) containing 2 wt.% nanosized SiCp were fabricated through accumulative roll bonding (ARB). The microstructure and mechanical properties of Mg/2 wt.%SiCp nanocomposites are reported for various ARB cycles. To evaluate microstructure of the nanocomposites, the field emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), and transmission electron microscope (TEM) were applied. After fourteen ARB cycles, the nanocomposite showed a homogeneous distribution of reinforcements and a significant reduction in average matrix grain size. Meanwhile, the nanocomposite revealed a higher percentage of recrystallization and lower intensity of basal texture as compared to monolithic Mg. Mechanical properties were investigated through tensile and microhardness tests. The strength and elastic modulus and microhardness of Mg/2 wt.%SiCp were found to be improved significantly from eight ARB cycles and reach maximum values at fourteen ARB cycles. The ultimate tensile strength, yield strength, microhardness, and elastic modulus of Mg/2 wt.%SiCp are considerably increased by 17.6%, 61.0%, 72.7%, and 80.8% as compared to raw Mg, respectively.

Microstructural Studies of Aluminium 7075-Silicon Carbide-Alumina Metal Matrix Composite

The modern development in the field of science and technology has created a demand for many advanced engineering materials. In recent days, aluminium related metal matrix composite is a probable material for many applications such as transport, aerospace, marine and automobile applications. In this paper, experiments were conducted on composite having various weight fractions of SiC and Al2O3 particulates fabricated by stir casting method. Characterization studies were conducted on the Al 7075 alloy and composite samples to assess the hardness and microstructural properties. Final samples were tested for hardness using vickers hardness machine. Microstructure examination was conducted by optical microscope. Microstructure of the composite samples reveals the presence and homogeneous distribution of reinforcements in the Al 7075 matrix. The hardness of aluminium metal matrix composites was increased due to the addition of silicon carbide and alumina reinforcements.

Development of Aluminium Based Silicon Carbide Particulate Metal Matrix Composite for Spur Gear

MMCs are made by dispersing a reinforcing material into a metal matrix. They are prepared by powder metallurgy and casting, although several technical challenges exist with casting technology. Achieving a homogeneous distribution of reinforcement within the matrix is one such challenge, and this affects directly on the properties and quality of composite.The aluminum alloy composite materials consist of high strength, high stiffness, more thermal stability, more corrosion and wear resistance, and more fatigue life. aluminum alloy materials found to be the best alternative with its unique capacity of designing the materials to give required properties.In this work a composite is developed by adding silicon carbide in Aluminum metal by mass ratio 2.5%, 5%, 7.5% and 10%. The composite is prepared by stir casting technique. Mechanical tests such as hardness test, microstructure test are conducted. It is proposed to use this material for power transmitting elements such as gears which are subjected to continuous loading. Finally modeling and finite element analysis of gear is done using CATIA and ANSYS 14.0.In case of increased silicon carbide content, the hardness, and material toughness are enhanced. From the results it is concluded that composite material such as aluminum silicon carbide is one of the option as a material for power transmission gears.

The effect of ball milling on the microstructure of powder metallurgy aluminium matrix composites reinforced with MoSi 2 intermetallic particles

Six hot extruded Al–Mg–Si composites reinforced with 15 vol.% of MoSi 2 intermetallic particles were processed by powder metallurgy, varying reinforcement size and high energy ball milling time. The relation between these parameters and matrix microstructure, final reinforcement size and particle distribution has been investigated. Reinforcement distribution was quantified through the coefficient of variation of the mean near-neighbour distance, COV( λ m), which demonstrated to be the most sensitive method to characterize this feature. The results show that by increasing milling time homogeneity of MoSi 2 distribution significantly increased, achieving a COV( λ m) = 0.41, independently of initial reinforcement size. Increasing milling time, the submicrometric matrix grains and reinforcing particles together with the homogeneous reinforcement distribution gave rise to higher tensile properties without loss of ductility.