Volume Fraction Of Reinforcement Research Articles

Influence of boron carbide content on the microstructure, tensile strength and fracture behavior of boron carbide reinforced aluminum metal matrix composites

AbstractIn the present work, an indigenously developed low cost modified stir casting technique is developed for the processing of 6061 Al‐B4C composites containing high‐volume fraction of boron carbide particles (up to 20 vol. %). The influence of varying reinforcement content on the spatial distribution of boron carbide in the aluminum matrix is qualitatively characterized using scanning electron microscope. At a lower volume fraction of reinforcement, wide particle free zone and large interparticle spacing were observed in the matrix while the composite with high reinforcement content displayed relatively homogeneous and discrete particle distribution. X‐ray diffraction analysis confirms the presence of only aluminum and boron carbide diffraction peaks, indicating that no significant reaction occurs during composite processing. The tensile behavior of composites revealed that strength and ductility are influenced by varying particulate content. The quantitative analysis of strengthening mechanism in the casted composites showed that higher volume fraction of boron carbide lead to larger values of thermal dislocation strengthening, grain size and strain gradient strengthening. The morphology of fracture surfaces reveals the presence of dimple network and the average size of dimples gradually decreases with the increase in particulate content, which indicates the co‐existence of ductile and brittle fracture.

Buckling of functionally graded graphene reinforced conical shells under external pressure in thermal environment

In the present research, buckling analysis of composite laminated conical shells reinforced with graphene sheets is investigated. Graphene sheets as reinforcements are distributed in each lamina. Volume fraction of graphene in each layer may be different which results in a piecewise functionally graded conical shell. First order shear deformation shell theory, Donnell kinematic assumptions and von Kármán type of geometrical non-linearity are used to establish the governing equations of the conical shell and the associated boundary conditions. The pre-buckling forces of the shell are obtained employing a membrane analysis. The linear stability equations are developed using the adjacent equilibrium criterion. These equations are discreted by means of the generalised differential quadratures across the shell length and Fourier expansion through the circumferential direction. An eigenvalue problem is obtained which yields the critical buckling pressure of the conical shell in thermal environment and the circumferential mode number at the onset of buckling. Comparison studies are provided for graphene reinforced and conventional composite laminated cylindrical shells and also isotropic conical shells with and without thermal environment. Afterwards parametric studies are given for buckling of functionally graded graphene reinforced composite laminated conical shells in thermal environment with different boundary conditions. It is shown that, temperature elevation decreases the critical buckling pressures of the conical shell significantly. Also buckling pressure of the shell may be enhanced through a piecewise functionally graded distribution of volume fraction of reinforcements.

The influence of cold and detonation thermal spraying processes on the microstructure and properties of Al-based composite coatings on Mg alloy

Al-based metal matrix composite (Al-MMC) coatings were produced on AZ91 magnesium alloy substrates utilizing two distinct coating techniques, i.e. cold spraying (CS) and detonation thermal spraying (DS), and the microstructure, hardness, bonding strength and corrosion behaviour were comparatively studied. The results showed that the CS process, which was featured with high kinetic and low thermal input energies, led to the dense structure resulted from the high velocity impact of particles at the solid state. The DS processed coatings showed relatively high porosity owing to the melting and oxidation involved during the deposition. But, due to the high fraction of metallurgical bonding of deposited splats, the DS coating demonstrated superior mechanical properties in terms of hardness and bonding strength when the porosity was reduced at higher volume fraction of the ceramic reinforcement. With increasing the volume fraction of ceramic particles in the source powder, the transitional fracture from the adhesive to cohesive mode was observed for both CS and DS processed composite coatings. In addition, compared to the AZ91 alloy substrate, both CS and DS composite coatings showed improved corrosion resistance.

Microstructural and mechanical behavior of blended powder semisolid formed Al7075/B 4 C composites under different experimental conditions

Abstract This work aimed to fabricate B4C reinforced aluminum matrix composites via blended powder semisolid forming that is an implementation of the benefits of semisolid forming to the powder metallurgy. Al7075 elements were incrementally added to ethanol solution under mechanical mixing. Al7075 constituents and B4C particles were blended in a high energy ball mill. Cold compacted Al7075/B4C blends were pressed at semisolid state. The effects of the size of the matrix (20, 45 and 63 μm), reinforcing volume fraction (5%, 10% and 20%) and semisolid compaction pressure (50 and 100 MPa) on the morphology, microstructure, density, hardness, compression and bending strength were thoroughly analyzed. Experimental results revealed that the highest microstructural uniformity was achieved when large B4C particles (45 μm) were distributed within the small particles (20 μm) of the matrix phase. Composites with matrix particles larger than reinforcing phase indicated agglomerations in loadings more than 10% (volume fraction). Agglomerated regions resisted against penetration of the liquid phase to the pores and lowered the density and strength of these composites. Composites with 20 μm Al7075 and 20% (volume fraction) 45 μm B4C powder pressed under 100 MPa exhibited the highest values of hardness (HV 190) and compressive strength (336 MPa).

The energy‐based multistage fatigue crack growth life prediction model for DRMMCs

AbstractA complex closed form expression for the multistage fatigue crack growth life has been developed to predict the fatigue life of discontinuous reinforced metal matrix composites. The multistage fatigue crack growth model includes the microstructural features of composite such as aspect ratio, volume fraction of reinforcement, constraint of fibre in the matrix, and interfacial bonding strength. It characterizes the fatigue damage evolution in various stages of crack nucleation/initiation and the growth of crack culminating in failure. A fatigue crack initiation model is presented, using energy balance equation, considering the nucleation process of phase transformation. The short crack growth life is estimated using the dependency of cyclic crack‐tip opening displacement that is directly correlated with the fatigue crack growth rate whereas the long crack growth life is evaluated using Li and Ellyin model. The sensitivity analysis of crack initiation model is performed to provide in‐depth knowledge on the mechanistic aspect. The sensitivity analysis shows that the little variation in the parameters “cyclic strain hardening exponent” (n′), “cyclic strength coefficient” (K′), and short crack length (asc) significantly affects the total fatigue crack growth life. It is observed that reinforcement increases the cyclic plastic deformation level and cyclic plastic zone size near the crack tip, under the total strain‐controlled conditions. The effect of total fatigue crack growth life is found to be significant in low cycle fatigue applications.

Draping Behavior of Carbon Non-Crimp Fabrics and Its Effects on Mechanical Performance of the Hemispherical Composites

In order to investigate the draping behavior of non-crimp fabrics (NCFs), two types of carbon NCFs with tricot-chain stitches or chain stitches were formed on a hemispherical mould via a stretch forming process. The shear angle and forming defects of the fabrics were measured on the hemisphere, under different blank holder forces (BHFs). The results showed that increasing BHF could enhance the shear angle slightly, reduce the asymmetry for the deformation of the fabrics, and change the main type of the process-induced defects. Besides, compression tests were performed on the corresponding composite components. By analyzing the change of fiber volume fraction and structural parameters of the textile reinforcements, the effects of draping behavior of NCFs on the mechanical performance of the composites were studied. The results reveal that draping process has distinguishable impacts on the mechanical properties of the final components, which is closely related to the stitching pattern of the NCFs.

Dry sliding wear behavior of Mg-SiC nanocomposites with high volume fractions of reinforcement

The dry sliding wear behaviors of Mg based nanocomposites were investigated using the ball-on-disk wear tester. The friction coefficient of Mg nanocomposite reinforced with 15 vol% SiC nanoparticles is much higher than pure Mg and AZ31B alloy. Its wear resistance is about 23 times higher than that of pure Mg. Analysis on the surface and debris suggests that the delamination mechanism of Mg has been overcome by the addition of high volume fraction nanoparticles, and the dominant wear mechanism of the Mg-SiC nanocomposites is oxidation.

Strengthening of Al-Fe3Al composites by the generation of harmonic structures

Strengthening of alloys can be efficiently attained by the creation of harmonic structures: bimodal microstructures generated by controlled milling of the particulate precursors, which consist of coarse-grained cores embedded in a continuous fine-grained matrix. Here, we extend the concept of harmonic structures to metal matrix composites and analyze the effectiveness of such bimodal microstructures for strengthening composites consisting of a pure Al matrix reinforced with Fe3Al particles. Preferential microstructural refinement limited to the surface of the particles, where the Fe3Al phase is progressively fragmented, occurs during ball milling of the Al-Fe3Al composite powder mixtures. The refined surface becomes the continuous fine-grained matrix that encloses macro-regions with coarser reinforcing particles in the harmonic composites synthesized during subsequent powder consolidation. The generation of the bimodal microstructure has a significant influence on the strength of the harmonic composites, which exceeds that of the conventional material by a factor of 2 while retaining considerable plastic deformation. Finally, modeling of the mechanical properties indicates that the strength of the harmonic composites can be accurately described by taking into account both the volume fraction of reinforcement and the characteristic microstructural features describing the harmonic structure.

Study on mechanical and ballistic performances of boron carbide reinforced Al 6061 aluminum alloy produced by powder metallurgy

Abstract In this study, the density, hardness, impact toughness, transverse rupture strength, tensile strength and ballistic resistance of Al 6061 alloy reinforced with boron carbide (B4C) powders were studied to elucidate the influence of the ceramic content and production process on the physical and ballistic properties of the resulting composites. Powder-metallurgy and hot-extrusion techniques were used to manufacture the Al 6061-based metal matrix composites reinforced with 5 wt%, 10 wt%, 15 wt% and 20 wt% B4C. The hot-rolling process was performed on a group of specimens to examine the effect on the mechanical and ballistic behaviors. The results revealed that a uniform particle distribution was achieved in a matrix structure and higher relative density values were measured in all specimens. The hardness, transverse rupture strength and tensile strength were improved and impact toughness was decreased with increasing volume fraction of B4C particle reinforcement for both hot-extruded and hot-rolled specimens. The highest flexural strength was measured in hot-extruded specimens and the maximum tensile strength was obtained in hot-rolled composites. The deformation tests showed that transgranular cracking occurred on B4C particles and particles were retained in the matrix. The hot-extruded, hot-rolled and laminated with two hot-rolled specimens were subjected to a ballistic test with a 7.62 mm × 51 mm M80 projectile for Type III and the ballistic resistance investigated by analyzing the hole surface in the armor. The hot-rolled and hot-extruded specimens were perforated in ballistic tests and exhibited ductile behavior with the petal failure mechanism. The two-layer hot-rolled specimens successfully absorbed the impact energy of the bullet with the lowest depth of penetration and smooth bulging.

Effect of Reinforcement Volume Fraction on the Wear Behavior of Al-SiCp Composites Prepared by Spark Plasma Sintering

Most investigations on MMCs were carried out using conventional methods. Employing a different approach, this study concentrated on compaction, hardness and wear behavior of Al-SiC composites with different reinforcement volume fractions (5–15%) by spark plasma sintering method. Hardness and density test results of the composite samples used in this study were significantly higher than conventionally produced composites. Such increase in density and hardness resulted in lower wear rate. To study the effect of applied load on samples wear behavior, wear tests were carried out under 1, 3 and 10 N loads with 0.07 m/s sliding rate. Results revealed that in all the applied loads, composite samples had lower wear rates and lower friction coefficients than those of unreinforced aluminum. Conversely, increase in volume fraction of reinforcement particles led to decrease in wear rates and friction coefficients of the composite specimens which were more tangible in Al-15%SiC sample. Obtained data showed that by increasing the applied load, friction coefficient and wear rate increased in all the samples. Also dominant wear mechanism was determined using SEM micrographs of sample surfaces after wear tests.

Experimental investigation and modelling of hot forming B4C/AA6061 low volume fraction reinforcement composites

This paper presents an experimental investigation of the hot deformation behaviour of 15% B4C particle reinforced AA6061 matrix composites and the establishment of a novel corresponding unified and physically-based visco-plastic material model. The feasibility of hot forming of a metal matrix composite (MMC) with a low volume fraction reinforcement has been assessed by performing hot compression tests at different temperatures and strain rates. Examination of the obtained stress-strain relationships revealed the correlation between temperature and strain hardening extent. Forming at elevated temperatures enables obvious strain rate hardening and reasonably high ductility of the MMC. The developed unified material model includes evolution of dislocations resulting from plastic deformation, recovery and punching effect due to differential thermal expansion between matrix and reinforcement particles during non-steady state heating and plastic straining. Good agreement has been obtained between experimental and computed results. The proposed material model contributes greatly to a more thorough understanding of flow stress behaviour and microstructural evolution during the hot forming of MMCs.

Comparative investigation on microstructures and mechanical properties of (TiB + TiC)/Ti-6Al-4V composites from Ti-B4C-C and Ti-TiB2-TiC systems

Two percentages of TiB + TiC reinforced Ti-6Al-4V composites from Ti-B4C-C and Ti-TiB2-TiC systems were fabricated by reactive hot-pressed sintering. Their microstructures and mechanical properties involving elastic modulus, Vickers hardness, bending strength and wear property were investigated comparatively. The experimental results show that needle-like TiB whiskers and near-equiaxed TiC particles are evenly distributed in the Ti-6Al-4V matrix. The mechanical properties of the (TiB + TiC)/Ti-6Al-4V composites are closely related with the nominal composition and synthesis system of TiB + TiC reinforcement and the microstructures of composites. With increasing the nominal volume fraction of reinforcement, both elastic modulus and Vickers hardness increase more or less and the bending strength decreases in varying degrees. A certain increase of pores in the composites with the sintering temperature increasing to 1300 °C can markedly affect the bending strength. Moreover, no matter what the sintering temperature and nominal volume fraction of reinforcement, the elastic modulus and Vickers hardness of composites from the Ti-TiB2-TiC system are higher than those from the Ti-B4C-C system. Similarly, the composites from the Ti-B4C-C system present better abrasion resistance than those from the Ti-TiB2-TiC system due to the difference of interfacial bonding between the TiC particles and Ti-6Al-4V matrix in the two kinds of composites.

Low-velocity impact response of FG-GRC laminated beams resting on visco-elastic foundations

This paper presents an investigation on the low-velocity impact response of a functionally graded graphene reinforced composite (FG-GRC) laminated beam subjected to a transverse impact load. The beam is assumed to rest on visco-Pasternak foundations in thermal environments. Each layer of the laminated beam has the same thickness, but the volume fraction of graphene reinforcement for the layers may be different and vary along the thickness direction in a piece-wise functionally graded pattern. The temperature dependent material properties of graphene reinforced composites (GRCs) are estimated by an extended Halpin–Tsai model, where the graphene efficiency parameters are introduced and determined from the results of molecular dynamics (MD) simulations. The impactor that applies the impact load to the beam may act at any position of the beam for which the central impact is treated as a special case. The contact process follows a modified Hertz model. The linear motion equations of the FG-GRC laminated beam are established based on a higher-order shear deformation beam theory when the impact position is arbitrary, whereas the nonlinear motion equations are obtained only for the central impact case. The motion equations of the beam and the dynamic equation of the impactor are then solved simultaneously by the Runge–Kutta approach. The numerical results illustrate the influences of functionally graded graphene distribution, foundation stiffness, temperature variation and different impactor velocities on the central deflection of the FG-GRC laminated beam as well as the contact force between the beam and the impactor.

Direct and inverse multi-scale analyses of arbitrarily functionally graded layered hollow cylinders (discs), with different shaped reinforcements, under harmonic loads

A multi-scale model is proposed to investigate arbitrarily functionally graded hollow cylinders (discs), with fibers, particles, or disc-shaped reinforcements, subjected to harmonic loading conditions. The stress analyses are performed by dividing the cylinders (discs) into several layers each with homogeneous properties, which are functionally graded through the thickness of the structures, with varying microstructural details. Good agreement can be obtained by comparing the present stress distributions against other analytical solutions used as boundary conditions or obtained for homogeneous and continuously graded structures. Furthermore, the Mori-Tanaka model is used to generate effective properties of each layer reinforced with fibers, particles or disc-shaped inclusions. The stress distributions in the cylinders along the radial direction are effectively investigated with the influence of either the shape or the volume fraction of reinforcements. Finally, the particle swarm optimization technique is combined with the present framework to provide inverse calculations for microstructural details, in the effort of finding proper inclusion volume fractions or minimizing the shear stress along the radial direction, which are necessary for the design of functionally graded structures. The present analysis for arbitrarily FG cylinders under arbitrary loading conditions provides benchmark solutions for other future analytical and numerical methods.

Simulation of mushy state solidification in stir casting

PurposeStir casting is a promising technique used for the manufacture of Al-SiC metal matrix composites. The clustering of reinforcement particles is a serious concern in this production method. In this work, mushy-state solidification characteristics in stir casting are numerically simulated using computational fluid dynamics techniques to study the clustering of reinforcement particles.Design/methodology/approachEffects of process parameters on the distribution of particles are examined by varying stirrer speed, volume fraction of reinforcement, number of blades on stirrer and diameter ratio (ratio of crucible diameter to stirrer diameter). Further, investigation of characteristics of cooling curves during solidification process is carried out. Volume of fluid method in conjunction with a solidification model is used to simulate the multi-phase fluid flow during the mushy-state solidification. Solidification patterns thus obtained clearly indicate a strong influence of process parameters on the distribution of reinforcement particles and solidification time.FindingsFrom the simulation study, it is observed that increase in stirrer speed from 50 to 150 rad/s promotes faster solidification rate. But, beyond 100 rad/s, stirrer speed limit, clustering of reinforcement particles is observed. The clustering of reinforcement particles is seen when volume fraction of reinforcement is increased beyond 10 per cent. When number of blades on stirrer are increased from three to five, an increase in solidification rate is observed, and an uneven distribution of reinforcement particles are observed for five-blade geometry. It is also seen from the simulation study that a four-blade stirrer gives a better distribution of reinforcement in the molten metal. Decrease in diameter ratio from 2.5 to 1.5 promotes faster solidification rate.Originality/valueThere is 90 per cent closeness in results for simulation study and the published experimental results.

Characterization of Stir Cast Aluminium Silicon Carbide Metal Matrix Composite

Aluminium silicon carbide metal matrix composites (Al-SiC MMC) are gaining wider acceptance in various fields like aerospace, aircrafts, automobile, substrate in electronics, turbine blades, etc, due to their high strength, stiffness, high corrosion and wear resistance, good thermal and electrical properties and good damping capability. In this work Al-SiC MMCs are fabricated by mixing molten aluminium with Silicon carbide by the aid of mechanical stirring, called stir casting method. Also in this work, the stir casting process parameters are optimized within the range to obtain good mechanical characteristics and uniform mixing of reinforcement, which is a major concern in stir casting. The processing parameters that were investigated include stirrer speed, volume fraction of reinforcement, number of blades on stirrer and diameter ratio. Microstructure observed through optical microscope was correlated to clustering tendency of reinforcement particles. The results of mechanical characterization study and microstructure study show that the stirrer speed, volume fraction of reinforcement, diameter ratio, and number of blades on stirrer appears to have significant effect on mechanical properties and clustering tendency of reinforcement particles

Study on Mechanical Alloying of TiB<sub>2</sub> Particulate Reinforced Titanium Matrix Composites

TiB2 particulate reinforced titanium matrix composites were prepared by mechanical alloying and spark plasma sintering. Volume fraction of TiB2 powders in the composites are 5%, 10%, 15%. The effect of milling time and the volume fraction of reinforcement on microstructure and properties of the composites were studied. The results show that with increasing milling time, the size of powder particles decreases, quantity of them increases, and microstructure of the sintered samples becomes finer and more uniform. When milling time reaches 30h, the trend of powder agglomeration increases, the downward trend of the particle size becomes slowly. With the milling time, the density of titanium matrix composites is on the rise. The density of 10vol%TiB2 particulate reinforced titanium matrix composites can reach 4.799 g/cm3, with 30h milling time and sintering at 900°C. The density and hardness of the composites increase with increasing the volume fraction of TiB2. When the volume fraction of TiB2 is 15%, after milling 10h and sintered at 800°C, the density and hardness of the composites can reach 4.713g/cm3 and HV851.58.

Mechanical behavior of Al-matrix nanocomposites produced by stir casting technique

Aluminium matrix composites (AMCs) have emerged as a material for aircraft and automotive applications owing to its superior specific strength, stiffness, controlled co-efficient of thermal expansion, light weight and excellent wear resistance. The current research study emphases on the production of aluminium (AA6082) matrix composites reinforced in different volume fractions of alumina (50nm) particulates by using stir casting method. The volume fraction of reinforcement was varied from 0% to 3% in stages of 1%. The produced composites were examined by using scanning electron microscope (SEM). Hardness and tensile strength of the composite was studied. The mechanical properties of these composites were compared with matrix alloy. Microstructural results revealed the homogeneous distribution of nano alumina particles in the matrix. The test results revealed that the hardness and tensile strength of the composite increase with an increase in the volume fraction of alumina particle content, this may be due to good interfacial bonding between the reinforcement and the matrix.

Temperature effect on mechanical and tribological characterization of Mg–SiC nanocomposite fabricated by high rate compaction

In this paper, dynamic compaction is employed to produce Mg–SiC nanocomposite samples using a mechanical drop hammer. Different volume fractions of SiC nano reinforcement and magnesium (Mg) micron-size powder as the matrix are mechanically milled and consolidated at different temperatures. It is found that with the increase of temperature the sintering requirements is satisfied and higher quality samples are fabricated. The density, hardness, compressive strength and the wear resistance of the compacted specimens are characterized in this work. It was found that by increasing the content of nano reinforcement, the relative density of the compacted samples decreases, whereas, the micro-hardness and the strength of the samples enhance. Furthermore, higher densification temperatures lead to density increase and hardness reduction. Additionally, it is found that the wear rate of the nanocomposite is increased remarkably by increasing the SiC nano reinforcement.

Finite Element Analysis of Tool Particle Interaction, Particle Volume Fraction, Size, Shape and Distribution in Machining of A356/SiCp

The application of particulate reinforced metal matrix composite (PRMMC) has been increasing due to its superior strength and wear characteristics. The unique properties of PRMMC vary with respect to the volume fraction of reinforcement. In this paper a 2D Finite Element Analysis of A356/SiCp MMC during orthogonal turning is modelled and simulation is carried out using Abaqus as FE code. The main purpose of this study is to analyse the tool particle interactions and effect of volume fraction, size, shape and distribution during machining of A356/SiCp. In this model Lagrangian formulation approach is used. Johnson cook material model is employed for A356 and brittle cracking model is used for SiCp. Penalty contact method is used as the friction formulation with hard contact algorithm. The FE simulations are done for 0, 6, 12 and 15% of SiCp by volume, 60 and 12 micron of SiCp by size, circular & irregular shapes and uniform & irregular distribution of SiCp. The FE model created is validated with experimentally measured data, chip formation is simulated, tool-particle interaction is studied and effect of various volume fractions, sizes, shapes and distributions of SiCpin chip formation and stress pattern are analysed during the machining process using PCD tool insert.