Distribution Of Reinforcement Particles Research Articles

Characteristics of Fe-Yttria Composites Fabricated by Powder Metallurgy Method

This study is focused on fabricating and characterizing iron (Fe) composites prepared by powder metallurgy route reinforced with varying weight of Yttria (Y2O3). Composites were prepared based on 5 wt. % to 15 wt. % of reinforcement powder with particle size ranging from 1-10µm. Pure Fe matrix composites were also prepared for comparison purpose. This paper will report the microstructure, bulk density and micro hardness values of the composites. Powder characterization and microstructures of the composites were examined using Scanning Electron Microscope (SEM) which indicated homogenous distribution of reinforcement particles in the metal matrix. Bulk density of the composites was calculated using standard Archimedean method showing decreasing values as the weight percentage of Y2O3 increases. Micro-hardness was measured using micro-Vickers hardness instrument. The data obtained shows that the Fe-Y2O3 composites samples possessed superior hardness value with the increasing quantity of reinforcement compared to the unreinforced Fe composite.

Characterization of electrodeposited Ni–SiC–Cg nanocomposite coating

Nickel–silicon carbide–graphite (Ni–SiC–Cg) nanocomposite coating was deposited onto the steel (St-37) substrate by electrochemical plating method. The influence of pH parameter on the mechanical properties and morphological features was studied. The coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Elemental mapping analysis system, and field emission scanning electron microscopy (FE-SEM) techniques. Besides, the microhardness of specimens was measured by Micro hardness Tester. Based on XRD results, the dominant phases with high crystallinity degree were nickel, silicon carbide and graphite. Microscopic observations illustrated that all the coatings had a cluster like structures which consisted of some fine sphere particles with an average crystallites size of 60nm. Among of all coatings, the specimen at pH equal to 4.8 presented an appropriate morphology as well as lower porosity with high grain boundaries. Moreover, elemental mapping spectra exhibited a homogenous distribution of nickel, silicon and carbon particles. However, the distribution of silicon particles into nickel matrix at pH=4.8 was higher than the other samples. Also, mechanical properties of the attained coatings were improved with increasing of pH values up to 4.8 (593 HV) which is in agreement with microstructural characteristics. Therefore, obtaining of the optimum pH value is the major parameter in electroplating of Ni based nanocomposite which affected microhardness and distribution of reinforcement particles into the matrix.

The effect of thermal cycling by electron-beam surfacing on structure and wear resistance of deposited M2 steel

Structural features of coatings obtained by multiple-pass electron beam cladding of M2 steel powder on steel substrates have been investigated. It is established that a multi-modal size distribution (d1=3.8μm, d2=0.65μm, d3<0.25μm) of reinforcement particles was generated in the carbide subsystem of the clad layer. The volume content of secondary carbides M6C and residual austenite of matrix can be changed in the wide range depending on the thermal cycling induced by incident electron beam. The higher is the content of the retained austenite in the coating, the higher is the wear resistance of the coating due to γ→α′ transformation in cooling and precipitation of secondary carbides in the matrix grains.

Optimisation of mechanical milling process for production of AA 7075/(SiC or TiB2) composite powders

The present work concerns the processing of composite powders based on 7075 aluminium alloy by mechanical milling. A premixed powder (Alumix 431D, Ecka Granules, Germany) was used as the matrix material, and two different ceramic reinforcements (SiC and TiB2) were chosen as reinforcements. The main objective was to evaluate the effect of the content and addition method of the process control agent as well as the content and type of reinforcement on the microstructural and morphological evolutions of the powder particles during milling process and the as milled properties of the processed materials. Results showed that regardless of the starting composition, alloying took place through three stages, in which deformation, cold welding and fracturing of powder particles were the main mechanisms involved respectively. The mechanically milled composite powders showed a fine and homogenous distribution of reinforcement particles. A higher content of reinforcement resulted in a lower crystalline size for the milled powders (∼18 nm for composite powders containing 15 vol.-% ceramic particles).

Course of Solidification Process of AlMMC – Comparison of Computer Simulations and Experimental Casting

The aim of the paper is to present the possibilities of computational simulations for the casting of aluminum matrix composite (AlMMC) reinforced with ceramics based on experimental data. The comparison of simulation and experimental results concerned the solidification process i.e. the course of solidification, temperature distribution and final arrangement of reinforcement particles. First, we have performed the experimental gravity casting of the aluminum matrix alloy AK12 (AlSi12CuNiMg2) and the composites AK12/SiC and AK12/Cg reinforced with silicon carbide SiC and glass carbon Cg, respectively, into the sand mold. During the experiment we have recorded the temperature using the ThermaCAM photometer system as well as in the selected point inside the sand mold. Using experimental data we have carried out the numerical calculations according to the methods and procedures contained in the program ANSYS Fluent 13. We have based the simulations on the two-dimensional model in which the Volume of Fluid (VOF) and enthalpy methods have been applied. The former is to describe two-phase system (air-composite matrix free surface, volume fraction of particular continuous phase) and the latter shows modeling of the solidification process of the alloy and composite matrix. We have used the Discrete Phase Model (DPM) to depict the presence of reinforcement particles. The assumption of the appropriate values of simulation parameters has shown that the simulation results are convergent with experimental ones. We have observed a similar course of the composite solidification (temperature change at the designated point), the temperature distribution and the arrangement of reinforcement particles for the simulation and experiment.

Metallurgical and mechanical characterization of stir cast AA6061-T6–AlNp composite

An attempt has been made to manufacture aluminium (6061-T6) matrix composites reinforced with aluminium nitride particles (AlNp) of size 3–4μ using indigenously developed modified stir casting method with bottom pouring arrangement in controlled argon environment. To improve the wettability of AlNp with molten Al matrix, 2% Mg has been added. AA6061–AlNp composites have been successfully produced at different weight percentages (viz 0, 5, 10, 15 and 20) of AlNp and their metallurgical and mechanical properties have been analysed. Macrohardness, microhardness, Yield strength and ultimate tensile strength of the composite have improved with the addition of AlNp in the Al matrix. Optical and SEM micrographs reveal the homogeneous distribution of reinforcement particles in the matrix and X-ray diffraction patterns ensure the dispersion of AlNp reinforcement in AA6061 matrix.

Effects of particle arrangement and particle damage on the mechanical response of metal matrix nanocomposites: A numerical analysis

The spatial distribution of reinforcement particles has a significant effect on the mechanical response and damage evolution of metal matrix composites (MMCs). It is observed that particle clustering leads to higher flow stress, earlier particle damage, as well as lower overall failure strain. In recent years, experimental studies have shown that reducing the size of particles to the nanoscale dramatically increases the mechanical strength of MMCs even at low particle volume fractions. However, the effects of particle distribution and particle damage on the mechanical response of these metal matrix nanocomposites, which may be different from that observed in normal MMCs, has not been widely explored. In this paper, these effects are investigated numerically using plane strain discrete dislocation simulations. The results show that non-clustered random and highly clustered particle arrangements result in the highest and lowest flow stress, respectively. The effect of particle fracture on the overall response of the nanocomposite is also more significant for non-clustered random and mildly clustered particle arrangements, in which particle damage begins earlier and the fraction of damaged particles is higher, compared to regular rectangular and highly clustered arrangements.

Microstructure and mechanical properties of Al–Al2O3 micro and nano composites fabricated by stir casting

Abstract Aluminum matrix composites (AMCs) reinforced with micro and nano-sized Al2O3 particles are widely used for high performance applications such as automotive, military, aerospace and electricity industries because of their improved physical and mechanical properties. In this study, in order to improve the wettability and distribution of reinforcement particles within the matrix, a novel three step mixing method was used. The process included heat treatment of micro and nano Al2O3 particles, injection of heat-treated particles within the molten A356 aluminum alloy by inert argon gas and stirring the melt at different speeds. The influence of various processing parameters such as heat treatment of particles, injection process, stirring speed, reinforcement particle size and weight percentage of reinforcement particles on the microstructure and mechanical properties of composites was investigated. The matrix grain size, morphology and distribution of Al2O3 nanoparticles were recognized by scanning electron microscopy (SEM), optical microscope (OM) equipped with image analyzer, energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Also, the hardness and compression strength of samples was investigated. The results showed the poor incorporation of nano particles in the aluminum melt prepared by the common condition. However, the use of heat-treated particles, injection of particles and the stirring system improved the wettability and distribution of the nano particles within the aluminum melt. In addition, it was revealed that the amount of hardness, compressive strength and porosity increased as weight percentage of nano Al2O3 particles increased.

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.

Evolution of reinforcement distribution in Al–B 4C composites during accumulative roll bonding

The distribution of reinforcement particles in the matrix of a composite is one of the most important microstructural features affecting properties. In this study, nanostructured Al–B 4C composite sheets were processed by accumulative roll bonding (ARB), and the effect of the number of ARB cycles on the distribution of the B 4C particles in the Al matrix was evaluated. From optical microscopic studies accompanied by the radial distribution function analysis, it was realized that the microstructure uniformity is improved by increasing the number of ARB cycles. It was in good agreement with bulk hardness measurements in which the standard deviation of the hardness values was decreased by progression of the ARB process. In addition, the X-ray diffraction peak profile analysis revealed that the area weighted mean crystallite size of the Al matrix decreases to the nanometric scale (114 nm) after seven ARB cycles.

Tribocorrosion Behavior of Aluminum/Alumina Composite Manufactured by Anodizing and ARB Processes

In the present work, tribocorrosion behavior of Al/Al2O3 composite strips manufactured by anodizing and accumulative roll bonding (ARB) processes was investigated. The alumina quantity was 0.48, 1.13, and 3.55 vol.% in the aluminum matrix. Tribocorrosion experiments were conducted using a ball-on-plate tribometer, where the sliding contact was fully immersed in 1 wt.% NaCl solution. The composite sample served as a working electrode and its open circuit potential (OCP) was monitored before, during, and after sliding. In order to characterize the electrochemical behavior of the surface before and after sliding electrochemical impedance spectroscopy (EIS) was used and wear was also measured. Furthermore, the influence of quantity and distribution of reinforcement particles in the matrix on OCP and EIS was evaluated. It was found that the quantity, shape, size, and dispersion of alumina particles in the aluminum matrix strongly affected the measured tribocorrosion characteristics. The results showed that inhomogeneous, lower quantity, fine, and acicular-shape alumina particles cause serious materials loss in tribocorrosion process.

Microstructure and tribological performance of an aluminium alloy based hybrid composite produced by friction stir processing

In this study, friction stir processing (FSP) was utilized to incorporate SiC and MoS 2 particles into the matrix of an A356 Al alloy to form surface hybrid composite. A constant tool rotation rate of 1600 rpm and travel speed of 50 mm/min with a tool tilt angle of 3° was used. The wear resistance of the processed samples improved significantly as compared to that of the as-cast alloy. Microstructural analyses showed a uniform distribution of reinforcement particles inside the nugget zone, and a MoS 2 rich mechanically mixed layer (MML) on the top of worn surface. This MoS 2 layer is considered to stifle plastic deformation and thus, to improve tribological properties of the alloy.

Fabrication of Al-Al₃Ti/Ti₃Al Functionally Graded Materials under a Centrifugal Force.

Fabrication of Al-Al3Ti functionally graded materials (FGMs) under the centrifugal force has recently attracted some attention. The controlled compositional gradient of the fabricated FGMs, the low cost of the process, and the good mold filling, are the main advantages of the centrifugal method (CM). Using the conventional CM techniques such as the centrifugal solid-particle method and centrifugal in-situ method, FGMs rings with gradually distributed properties could be achieved. As a more practical choice, the centrifugal mixed-powder method (CMPM) was recently proposed to obtain FGMs containing nano-particles selectively dispersed in the outer surface of the fabricated parts. However, if a control of the particles morphology, compound formulas or sizes, is desired, another CM technique is favored. As a development of CMPM, our novel reaction centrifugal mixed-powder method (RCMPM) has been presented. Using RCMPM, Al‑Al3Ti/Ti3Al FGMs with good surface properties and temperature controlled compositional gradient could be achieved. In this short review, this novel method will be discussed in detail and the effect of RCMPM processing temperature on the reinforcement particles morphology, size and distribution through the fabricated samples, will be reviewed.

Three-Dimensional Microstructure Visualization of Porosity and Fe-Rich Inclusions in SiC Particle-Reinforced Al Alloy Matrix Composites by X-Ray Synchrotron Tomography

Microstructural aspects of composites such as reinforcement particle size, shape, and distribution play important roles in deformation behavior. In addition, Fe-rich inclusions and porosity also influence the behavior of these composites, particularly under fatigue loading. Three-dimensional (3-D) visualization of porosity and Fe-rich inclusions in three dimensions is critical to a thorough understanding of fatigue resistance of metal matrix composites (MMCs), because cracks often initiate at these defects. In this article, we have used X-ray synchrotron tomography to visualize and quantify the morphology and size distribution of pores and Fe-rich inclusions in a SiC particle-reinforced 2080 Al alloy composite. The 3-D data sets were also used to predict and understand the influence of defects on the deformation behavior by 3-D finite element modeling.

Evolution of manufacturing parameters in Al/Ni3Al composite powder formation using blending and mechanical milling processes

Aluminu–matrix composites produced by Ni3Al intermetallic particles are increasingly used in aerospace and structural applications because of their outstanding properties. In manufacturing of metal–matrix composites using powder metallurgy blending and milling are important factors. They control the final distribution of reinforcement particles and porosity in green compacts which in turn, strongly affect the mechanical properties of the produced PM materials. This paper studies different conditions for producing composite powders with uniform dispersion of Ni3Al particles in aluminum powders and improved physical and mechanical properties. The results indicated that an intermediate milling time for fabrication of composite powder, better than prolonged and shortened ones, causes better microstructure and properties. It was shown that addition of 5 vol.% Ni3Al particles, produced by 15 h mechanical alloying to aluminum powders, and then 12 h blending operation provides an appropriate condition for producing Al–Ni3Al composite powder.

Influence of Ultrasonic Processing on Nano-Sized Particle Dispersion in Magnesium Matrix Nanocomposites

The parameters of ultrasonic processing have important effects on the distribution and dispersion of nano-sized particles in magnesium matrix nanocomposite (MMNC) fabrication. In order to learn more about the above effects and produce guidelines for the fabrication of MMNC, the acoustic cavitation and streaming effects produced by high intensive ultrasonic method with different frequency and power were experimented with water, glycerol, soybean oil and oil-water mixture respectively. The results showed that the acoustic cavitation and streaming were influenced by ultrasonic frequency and power as well as the depth of waveguide dipped into melts. The ultrasonic processing of the MMNC melts with 20kHz and 1.4kW greatly improved the dispersion and distribution of nano-sized reinforcement particles in MMNC.

Vertical Centrifugal Casting of Aluminum Matrix Particle Reinforced Composites

Centrifugal casting of composites gives rise to a certain distribution of reinforcement particles due to the natural liquid flow and solidification pattern. The particle rich regions are strongly influenced by rotational speed of the mold, particle size, relative density difference between particles and melt, initial pouring temperature, initial mold temperature, and by the nature of the particles added [1—3]. In the present work zirconia, silicon carbide, and ilmenite particles have been added to an aluminum—magnesium alloy and cast using a vertical centrifugal casting machine. The particle distribution and the resultant hardness variation have been analyzed. The particles are invariably associated with porosity. In the case of ilmenite particles, there is extensive reaction with the liquid metal. The combined effect of vol % of particles, porosity, and extent of reaction gives rise to a complex hardness variation. There is a substantial increase in hardness with particle addition. The particles tend to concentrate at the middle of the casting.

Numerical simulation of the effect of particle spatial distribution and strength on tensile behavior of particle reinforced composites

The spatial distribution of reinforcement particles significantly influences the tensile behavior of particle reinforced composites. In this study, we have modeled the effect of particle clustering in a model metal matrix composite, SiC particle reinforced Al. The SiC particles were modeled as purely elastic, while the Al matrix was modeled as elastic–plastic. To study the effect of particle distribution, the SiC particles were represented as two-dimensional circular particles of uniform diameter. Three particle distributions – ordered, random, and clustered were evaluated. The degree of particle clustering was quantified using the coefficient of variance of the mean near-neighbor distance method. The evolution of damage by particle fracture was included in the model. The cases for (a) all SiC particles having uniform fracture strength and (b) variable fracture strength were considered (using a Weibull distribution in strength). The effects of particle distribution were elucidated and are discussed.

About the Elaboration and Characterization of Fe-Based Composite with Friction Destination

The present research’ goal is the fabrication of Fe-based composite reinforced with oxide particles with special characteristics (wear, friction coefficient) for friction applications usually the Fe-based composite are obtained through melting and castings followed by other finishing operations. These technologies do not ensure a homogeneous distribution of reinforcement particles and that is why, the authors approached a PM specific technologies to obtained Fe-based composite. The Fe-based powder reinforcement with oxide particles obtained through mechanical alloying the powder was analyzed and characterized and then underwent the operation of milling in the planetary milling with ball, pressing and sintering at different temperatures and durations. SEM analysis had of identifying the distribution compounds into the Fe- matrix, their quantitative evolution and the influence of different parameters. The mechanical characteristics, wear and friction coefficient, were determined.

Effect of solidification rate on spatial distribution of SiC particles in A356 alloy composites

The damage and deformation behaviour of particulate reinforced metal matrix composites (PMMCs) can be highly sensitive to local variations in spatial distribution of reinforcement particles, which markedly depend on melt processing and solidification stages during production of PMMCs. The present paper attempts to study the effect of solidification rate on cluster formation in an Al–Si–Mg (A356) alloy composite reinforced with SiC particles and to explore the applicability of spatial functions to PMMC microstructures to quantify the degree of clustering. The observed amount of clustering in composites was evaluated with the nearest neighbour and local density statistics in terms of variations in dendrite arm spacings and solid fractions at the dendrite coherencies. The results indicate that the distribution of SiC particles is controlled by the secondary dendrite arms. Depending on dendrite arm spacings and particle content, clustering is most pronounced at distance scales ranging approximately between 150 and 500 μm, which is much larger as compared to the nearest neighbour distances.