Volume Fraction Of SiC Particles Research Articles

Wet erosive wear of alumina and its composites with SiC nano-particles

A study of the room temperature controlled wet erosive wear of monolithic alumina and its composites with nano-sized particles of SiC is presented. The worn surfaces suggest that grain pull-out phenomenon is the dominant mechanism determining the wear rate. Within the composites, a higher strength does not necessarily translate into a higher wear rate. Wet erosive wear depends on grain size, porosity, volume fraction of SiC particles in the composites and possibly the morphology of the grains (for monolithic alumina). For very nearly fully dense materials of about the same grain size, the composites are about 200% more wear-resistant than monolithic alumina. About 5% porous composites are at least 400% more wear-resistant than monolithic alumina of the same level of porosity.

The Constraint Effect And The Void Configuration In SiC Particle Reinforced Aluminium Alloy

The effect of constraint on the void configuration and coalescence are investigated experimentally using the 3-dimensional fracture surface observations under the SEM (Scanning Electron Microscope) and 3dimensional imaging analysis. The constraint effect is analysed by changing the specimen shape. The SiC particle reinforced Al 2025 aluminium alloy composites is used to test the ductile fracture by nucleation, growth and coalescence of micro voids under the different structure of materials and the different constraint conditions. The experimental results show that the void aspect ration is decreased with increases of SiC particle volume fraction in aluminium alloy and the final void volume fraction at fracture also changed by the specimen. The effect of the local constraint effect is analysed by using the 2dimensional FEM analysis. The results shown that the void shape agree with the experimental one qualitatively in different constraint specimens

Damage analysis of aluminum matrix composite considering non-uniform distribution of SiC particles

In this study, based on the fracture surface observations using an SEM (scanning electron microscope), a numerical unit model and 3-dimensional non-uniform model for FEM (finite element method) analysis are proposed by using Gurson's model as a constitutive equation. The effect of the non-uniform distribution of the SiC particle volume fraction and aspect ratio in the matrix are considered for the evaluation of the stress–strain relationship and the damage. The results show that the dimple fracture process of matrix aluminum alloy is well simulated, after a large amount of plastic deformation. The non-uniformity of the SiC particle volume fraction, aspect ratio and its locations have a strong effect on the local and global damage behavior and stress–strain relationships. It is shown that the fracture strain increases largely when the aspect ratio of SiC particles is 1.0 and it is distributed uniformly in the matrix. The numerical model is improved by considering the non-uniform effect on the tensile stress, fracture strain and local and global fracture.

Wear behaviour of an Al–12% Si alloy reinforced with a low volume fraction of SiC particles

Aluminium–silicon alloys reinforced with low volume fractions of SiC particles were prepared by the compocasting process. The wear behaviour of the unreinforced Al–12Si alloy and metal-matrix composites (MMCs) was investigated by using a block-on-ring test at room temperature under dry conditions. The results showed that the addition of a low volume fraction of SiC particles (2–8vol%) is a very effective way of increasing the wear resistance of the matrix alloy. Metallographic examinations revealed that the wear zone of the Al–12Si alloy consists of both hardened and deformation layers. The depth of the hardened layer depended on the applied load and was in the vicinity of 10–50μm. The formation of the hardened layer was related to the alignment and redistribution of fragmented eutectic phase to the surface region during sliding wear. Furthermore, the delamination of debris from the hardened layer was responsible for a higher wear loss observed in the Al–12Si alloy. The thickness of the hardened layer formed on the MMC specimens was reduced considerably by the incorporation of fragmented SiC particles. This layer exhibited higher hardness and wear resistance than that developed in the unreinforced alloy.

Pitting behavior of SiCp 2024 Al metal matrix composites

The effects of the volume fraction of SiC particulate reinforcements and the concentration of chloride ions in solution on the localized corrosion characteristics of SiCp/2024 Al metal matrix composites (MMC) were investigated. A scanning micro reference electrode (SMRE) technique was employed to study the dynamic process of pitting initiation and development on the surface of the composites at open-circuit potential. Potentiodynamic polarizations were performed to characterize the electrochemical behavior of the MMCs. The morphology of the localized attack on the MMC sample after corrosion tests were examined by scanning electron microscopy (SEM). The results of electrochemical measurement showed that the composites were less resistant to pit initiation than the corresponding unreinforced metrix alloy. Increase in the volume fraction of SiCp reinforcement in the SiCp/2024 Al composites resulted in a significant decrease of pitting potential. In situ potential mapping of active centers on the surfaces of the composites revealed that local breakdown of passivity and initiation of micro pitting corrosion could take place even at an open-circuit potential which was more negative than the pitting potential, and the number of active centers on the surfaces of the composites increased as the volume fraction of SiC particulates in MMCs increased. Micro-structural analysis indicated that pitting attack on the composites mainly occurred at SiCp-Al interfaces or inclusions-Al interfaces.

ＳｉＣ粒子強化２１２４アルミニウム合金複合材料の高速超塑性バルジ成形

High strain rate superplastic bulge forming of aluminum alloy matrix composite sheets reinforced by SiC particles was studied and compared to their deformation characteristics in a tensile test. Bulge forming test was performed at elevated temperatures using 36 mm diameter blank disks by gas pressure. The bulge shapes were successfully formed at high strain rate (about 0.1/s) at which superplasticity is observed in the tensile test. The superplastic formability of the composite with 25% volume fraction of SiC particles is better than that with 17% SiC, corresponding to the measured elongation in the tensile test. The limit bulge height of the sheet with the same SiC volume fraction is increased with increasing initial thickness. The higher forming gas pressure, namely the higher forming rate, lead to the uniform thickness distributions of the bulged part. The maximum thickness strain at the top of the bulge and the applied stress calculated from the forming gas pressure in bulge forming can be concerned with the elongation and the flow stress in the tensile test.

Microstructural characterization of Al 2O 3-SiC nanocomposites

Al 2O 3 composite ceramics containing 10 vol% SiC nanoparticles were prepared by pressureless sintering. SiC particles < 150 nm detach from the matrix grain boundaries during grain growth and are predominantly observed in intragranular positions, whereas larger SiC particles retain intergranular positions. Thermal expansion mismatch causes local residual tensile stresses in the matrix grains, giving rise to strain contrasts in TEM imaging; occasionally microcracking around intragranular inclusions ≥ 100 nm is observed in thin TEM foils. It appears that the volume fraction of intragranular SiC particles in the size range 100 < d < 150 nm should not exceed ≈ 0.5% in high strength/high toughness Al 2O 3-SiC nanocomposites. The interaction between propagating cracks and internal stress fields around intragranular inclusions forces a transgranular fracture mode. Grain boundary pinning by large intergranular SiC particles, in combination with solute drag inhibits matrix grain growth, while the presence of an amorphous phase at Al 2O 3 grain boundaries and Al 2O 3-SiC phase boundaries assists in densification. Excess liquid phase is exuded from the interfaces during consolidation and accumulates in large pores, stabilized by the accidental agglomeration of large SiC particles.

High strain rate superplastic flow stress and post-deformation mechanical properties of mechanically alloyed 2024 aluminium alloy reinforced with SiC particles

Composites consisting of 2024 aluminium alloys reinforced with volume fractions of 0, 5, 10, and 15 vol.-% of SiC particles were fabricatedfrom the mechanically alloyed powders by an optimised hot compaction and prestraining process. Fine and equiaxed grain structures with grain sizes of <1 μm were observed within the matrix of each alloy. The composite specimens were compressed at temperatures between 733 and 813 K with a wide strain rate range from 10−3 to 10 s−1. Two strain rate regions with different slopes from ∼ 5 × 10−1 s−1 were found in log (true stress–log (strain rate) curves. In the lower strain rate region of each alloy, the strain rate sensitivity values m were 0.03–0.16. The threshold stress σth for each alloy was estimated using an extrapolation procedure. A linear relationship was found between <disp-formula><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="splitsection10-m1.tif"/></disp-formula> and σth where Vf is the volume fraction of SiC particles. In the higher strain rate region of each alloy, m values greater than 0.3 were obtained at 773 K, which is very close to the solidus temperature of 775 K for 2024 aluminium alloy. Moreover, the maximum yield strength and elongation for each alloy at room temperature were also obtained in the specimens compressed at 773 K. Thus, it was found that the optimum temperature for the high strain rate superplastic processing of the composites was just below the solidus temperature of the 2024 aluminium alloy. The grain coarsening resulted in the decrease of post-deformation strength and ductility as well as the m value in hot compression above the solidus temperature.

The sliding wear resistance behavior of NiAl and SiC particles reinforced aluminium alloy matrix composites

The sliding wear resistance behavior of NiAl and SiC particles reinforced aluminum alloy matrix composites against S46C steel was studied. Experiments were performed within a load range of 3.5 N to 82.7 N at a constant sliding velocity of 0.15 m s 1. The sliding distance was 1000 m. Two types of composites, NiAlp/Al and SiCp/Al with different volume fractions (5 vol.% and 10 vol.%), were used. At low loads, where particles acted as load bearing constituents and prevented the aluminum matrix being directly involved in the wear process, the wear resistance of the SiCp/Al and the NiAlp/Al composites was superior to that unreinforced aluminium alloy. The wear rates of SiCp/Al and 10 pct NiAlp/Al composites at 3.5 N were about one factor of 10 lower than that of aluminium alloy. With increasing applied load, the wear rates of the composites increased to levels comparable to those of unreinforced matrix alloys. At 9.4 N, the wear rates of the composites and aluminum alloy were almost the same. The wear rates of NiAlp/Al and SiCp/Al composites above 13.5 N were much lower than those of aluminum alloy, since the severe wear of aluminum alloy at higher loads was hampered by incorporating the SiC or NiAl particles into the matrix. The wear rates of the counterface material, S45C steel, worn against aluminum alloy, were lower than those worn against the SiCp/Al composites at the entire applied load range. The wear rates were increased with the volume fraction of SiC particles. The NiAlp/Al composites wore the steel at the maximum wear rate at lower loads near 5 N. The NiAl particle was easily fractured when the applied load increased; as a result, the wear rates of steel against NiAlp/Al became smaller and were almost the same as those worn against aluminum.

The effects of pre-forge processing on forgeability and mechanical properties of co-sprayed aluminium-based MMCs

Pre-forge processes, comprising either extrusion or uniaxial/triaxial upset forging or pseudo-isostatic forging, were undertaken to reorganise the existing disposition of SiC particles known as TRS and/or eliminate residual porosity in co-sprayed aluminium-based MMCs. The objective of undertaking these processes is to improve forgeability and mechanical properties. The materials investigated are co-sprayed 2014 and 2618 aluminium alloys reinforced by 15% (volume fraction) of SiC particles. Billets of these materials were pre-forge processed at elevated temperatures and specimens were cut from them for forgeability and tensile tests performed at 450°C and room temperature, respectively. Forgeability and tensile properties depend on the orientation of the TRS and inherent cluster-pores relative to the direction of induced tensile stresses/strains. The pre-forge processes that increased forgeability did not, therefore, necessarily have the same effect on tensile properties. Forgeability increased as a result of triaxial/uniaxial upset forging and pseudo isostatic forging. Significant increases in tensile properties were observed in extruded and triaxially upset forged material only.

The syntheses of SiCp/Al nanocomposites under high pressure

The SiCp/Al nanocomposites were synthesized under high pressure. The reaction behavior between SiC particles and Al matrix within 2–6 GPa pressure range was determined. The high resolution electron microscopy (HREM) observation and the Vickers microhardness measurement show that the reaction is slight and that the adhesion of SiC particles to the Al matrix is good whether the reaction between them occurred or not. This offers an opportunity to tailor the nanocomposite mechanical properties by adjusting the synthesis temperature, pressure, and volume fraction of SiC particles.

Formation of Compositionally Graded Ni&amp;ndash;P Deposits Containing SiC Particles by Jet Electroplating

This paper presents a new electroplating process that uses an electrolyte jet containing SiC particles for the formation of electrodeposited Ni–P matrix composite coatings. The electrolyte jet remarkably increases the limiting current density in electroplating, so that the deposition rate will be approximately 10 times faster than that of conventional electroplating without an electrolyte jet. The fast deposition rate is caused by the thin diffusion layer adjacent to the cathode surface due to the electrolyte jet. The jet velocity determines the volume fraction of SiC particles in the range of 0∼30 vol% without changing the particle concentration in electrolytes. The phosphorus content in deposits is also controlled by the jet velocity without changing the phosphinic acid concentration in electrolytes. Hence, the jet electroplating realizes SiC particle/Ni–P deposits with a compositional gradient regarding the phosphorus content and the particle volume fraction with an extremely fast deposition rate.

Casting of SiC reinforced metal matrix composites

Composites based on two aluminium alloys (A536 and 6061) reinforced with 10% or 20% volume fraction of SiC particles were produced by gravity casting and a novel two-step mixing method was applied successfully to improve the wettability and distribution of the particles. The SiC particles were observed to be located predominantly in the interdendritic regions, and a thermal lag model is proposed to explain the concentration of particles. It was found that the SiC particles acted as substrates for heterogeneous nucleation of Si crystals in one of the cast composites. This observation can also be explained by the thermal lag model proposed.

Damage Analysis of Aluminum Matrix Composite Considering Non-Uniform Distribution of SiC Particles.

In this study, based on the fracture surface observations using a SEM (Scanning Electron Microscope), a numerical unit model and 3-dimensional non-uniform models for FEM (Finite Element Method) analyses are proposed using Gurson's model as a constitutive equation. The effect of the non-uniformity, the reinforcement volume fraction and the aspect ratio are considered for the quantitative evaluation of the stress-strain relationship of SiC particle-reinforced aluminum alloy. The results show that the dimple fracture process of the matrix aluminum alloy is well simulated after a large amount of plastic deformation. The non-uniformity of the SiC reinforcement locations and the aspect ratio have a strong effect on the local and global damage behavior and the stressstrain relations. It is shown that the fracture strain greatly increases when the aspect ratio of SiC particles is nearly 1.0, and the SiC particles are distributed uniformly. To improve both tensile strength and fracture strain, it is better to increase the SiC particle volume fraction rather than to increase the SiC particle aspect ratio. The numerical model is improved by considering the nonuniformity effect on the tensile stress and fracture strain.

Analysis of thermal residual stress in a thick-walled ring of duralcan-base Al-SiC functionally graded material

A ring-cutting test and an elastic theory were applied to evaluate the macroscopic residual stress in a thick-walled ring made of Al-SiC functionally graded material (FGM). The FGM ring specimens, with outer diameter 90 mm, radial thickness approximately 8.4 to 10 mm, and width 30 mm, were fabricated by the centrifugal casting method from an ingot of Duralcan F3D.20S of Al-20 vol pct SiC master composite. Because of a difference in centrifugal forces of SiC particles and of molten aluminum alloy, the rings had a graded composition of SiC particles in the radial direction. The volume fractions of SiC particles in each ring specimen varied in the range of 0 to 43 vol pct from the inner to the outer surface of the ring, depending on the applied mold spin speed. A ring diametral compression test was performed to validate an analytical formula based on the curved beam theory that can account for the graded properties of the material. Excellent agreement between the theory and the experiment was found. The residual stress was found to be generated by a cooling of Δt=140 K, which was from half the melting point corresponding stress-free condition to the ambient temperature. The hoop residual stresses in the FGM ring varied in the range of −50 to +35 MPa and from tension at the inner surface to compression at the outer surface because of the graded composition. With an increase in wall thickness and/or composition gradation, the residual stresses were found to increase.

Effects of SiCp size and volume fraction on the high cycle fatigue behavior of AZ91D magnesium alloy composites

High cycle fatigue tests (i.e., stress-controlled, axial) were conducted on monolithic AZ91D and AZ91D magnesinm alloy composites processed via squeeze casting and extrusion to contain either 15 gm or 52 gm size SiC particles, at both the 20% and 25% volume fraction reinforcement level. The effects of changes in SiC particle size and volume fraction on the high cycle fatigue behavior have been determined. In addition, the number of cracked particles on the fatigue fracture surfaces, as well as the level of damage beneath the fatigue fracture surfaces were quantified in order to determine the effects of particle size on the evolution of damage during fatigue and during overload failure. Commercial purity Mg specimens containing a large grain size were also tested in fatigue for comparison with the alloy and composite data.

Solidification of particle-reinforced metal-matrix composites

The solidification behavior of ceramic particle-reinforced metal-matrix composites (MMCs) is different from that of the bare matrix, not only because of the presence of the ceramic particles, but also due to their redistribution in the melt that results in nonhomogeneous thermophysical properties. The MMCs comprised of 10-to 15-μm SiC particles of varying volume fractions, dispersed uniformly in a modified aluminum A356 alloy by the melt stirring technique, were solidified unidirectionally in a thermocouple-instrumented cylindrical steel mold. The cooling rates were continually monitored by measuring temperatures at different depths in the melt, and the solidified MMCs were sectioned into disks and chemically analyzed for SiC volume fraction. The results point out that the cooling rate increased with increasing volume fraction of SiC particles. A small increase in the bulk SiC volume fraction of the cast MMC was observed due to particle settling during solidification. A one-dimensional enthalpy model of MMC solidification was formulated, wherein particle settling occurring in the solidifying matrix was coupled to the enthalpy equation by means of the Richardson-Zaki hindered settling correlation. A comparative study of simulations with experiments suggested that the thermal response of SiC particles used in this study was similar to that of single crystals, and their presence increased the effective thermal conductivity of the composite.

Effect of silicon additions on characteristics of carbon fiber reinforced aluminum composites during thermal exposure

The effects of Si additions on the behavior of high modulus carbon fiber reinforced aluminum matrix (CF/Al) composites during thermal exposure at 773 K for different times have been investigated. The composites were fabricated via hybridization with a small volume fraction of SiC particles using a pressure-casting process. The change of longitudinal tensile strength, the strength degradation of carbon fibers, and the microstructural observations on the interfaces of CF/pure Al composites and CF/Al-Si composites after thermal exposure undoubtedly indicate that the alloying element Si in an aluminum matrix can effectively prohibit the interfacial reactions at the fiber/aluminum interface and has positive effects on the characteristics of CF/Al composites.

Microfracture Analysis of SiC Reinforced Glass Composites by Acoustic Emission

SiC particulate reinforced glass matrix composites were fabricated by hot pressing. The volume fraction of SiC was changed from 0% to 30%. The elastic modulus of the fabricated composites was consistent with a law of mixture based on the micromechanics. In order to evaluate the mechanical properties of the materials we measured four-point bending strength and fracture toughness (K IC ) by Single Edge Pre-cracked Beam (SEPB) method. Acoustic emission (AE) tests were performed during four-point bending and fracture toughness tests We observed fracture surfaces after bending tests. The bending strength increased with increasing volume fraction of SiC particle. The bending strength of glass was 96MPa and that of the composite reinforced with 30 vol % SiC particle was 144 MPa. The fracture toughness K IC also increased with increasing volume fraction of SiC particle. The fracture toughness K IC of the composite reinforced with 30vol% SiC particle was 2.1 MPam 1/2 . The number of AE events increased with increasing volume fraction of SiC particle. However AE behavior during bending tests is different from that during fracture toughness tests The total number of AE during fracture toughness tests is more than that during bending tests.

Evaluation of Subcritical Crack Growth in SiC Particle Reinforced Al2O3 Composites

Subcritical crack growth behavior was examined in Al 2 O 3 matrix composites reinforced with 0, 10, 20 vol% SiC nanoparticles. Crack velocity exponent, was evaluated from two different methods. One is from the mean bending strength, and the other from the curve-fitting on 3-point bending strength data obtained under different testing conditions. A bending strength of the 20% SiC composite is about 970 MPa and shows no influence of both the environment and loading rate, while the monolithic Al 2 O 3 shows lower strength in air than in vacuum. The n value from the curve fitting on strength data is about 58 in the monolithic, 36 in the 10% SiC and 66 in the 20% SiC composite. Fracture toughness evaluated by the controlled-surface-flaw method show a similar tendency to the dependence of n value on the volume fraction of SiC particles. Taking the effect of grain size into consideration, it is expected that enough SiC particles can contribute to the improvement of both the fracture toughness and subcritical crack growth resistance.