SiCp Volume Fraction Research Articles

Crack and wear behavior of SiC particulate reinforced aluminium based metal matrix composite fabricated by direct metal laser sintering process

In this investigation, crack density and wear performance of SiC particulate (SiCp) reinforced Al-based metal matrix composite (Al-MMC) fabricated by direct metal laser sintering (DMLS) process have been studied. Mainly, size and volume fraction of SiCp have been varied to analyze the crack and wear behavior of the composite. The study has suggested that crack density increases significantly after 15 volume percentage (vol.%) of SiCp. The paper has also suggested that when size (mesh) of reinforcement increases, wear resistance of the composite drops. Three hundred mesh of SiCp offers better wear resistance; above 300 mesh the specific wear rate increases significantly. Similarly, there has been no improvement of wear resistance after 20 vol.% of reinforcement. The scanning electron micrographs of the worn surfaces have revealed that during the wear test SiCp fragments into small pieces which act as abrasives to result in abrasive wear in the specimen.

Influence of size and volume fraction of SiC particulates on properties of ex situ reinforced Al–4.5Cu–3Mg metal matrix composite prepared by direct metal laser sintering process

Direct metal laser sintering (DMLS) process has a great potential to prepare metal matrix composites (MMCs) in fabrication of arbitrary shaped jobs through rapid manufacturing. In the present work, silicon carbide particulates reinforced aluminium based metal matrix composite was developed by direct metal laser sintering process. Influences of SiC particulate (SiCp) on density, porosity and microhardness of the composite were investigated. It shows that SiCp having 300 mesh size provides higher density and lower porosity because of lower clustering effect. Higher microhardness was achieved at 1200 mesh of reinforcement because of lower grain size. Microhardness increases with increase of volume fraction of SiCp and higher value was achieved at high reinforcement content of 30vol.%. Microstructure was studied through scanning electron microscopy (SEM) and X-ray elemental mapping. Interfacial microstructure was also investigated and cracks were found in number of cases due to difference between co-efficient of thermal expansion of matrix alloy and SiCp.

The Microstructure and Mechanical Properties of SiCp-reinforced Copper Matrix Composites by Hot Pressing

SiCp-reinforced copper matrix composites with the reinforcement content of 30—50 vol.% were fabricated by hot pressing using Cu-coated and uncoated SiC powder. The microstructure and mechanical properties of the composites were studied. The results showed that with the increasing of SiCp volume fraction, the Brinell hardness of the composites increased first and arrived at a peak value, then decreased, while the bending strength decreased continuously. On the condition of same volume fraction of SiCp, the Brinell hardness and bending strength of the composites using coated powder were higher than that of the composites using uncoated powder. The annealing treatment lowered the Brinell hardness and bending strength of the composites. When the volume fraction of SiCp was 30 vol.%, the fracture mechanism of the composites showed a mixed manner of dimple and quasi-cleavage fracture. While the volume fraction of SiCp was 50 vol.%, the fracture behavior of the composites dominated in quasi-cleavage manner with seldom dimples.

Microstructure and mechanical performance of pulsed current gas tungsten arc surface engineered composite coatings on Mg alloy reinforced by SiCp

A new pulsed current GTA surface-modified process was used to fabricate composite layer on the surface of Mg alloy AZ31. Current pulsing enhances fluid flow, reduces temperature gradients and causes a continual change in the weld pool size and shape, so that it is responsible for refining the solidification structure in the composite layer. The observed grain refinement was shown to result in an appreciable increase in composite layer bend strength. Composite layers with lower scan speed have higher bend strengths and they also seem to have “good” metallurgical bond with the substrate thus showing better mechanical behavior than the other higher scan speeds used in this present study. The wear rate of the composite layer decreases linearly with increase in SiCp volume fraction and the wear resistance of composite layer varies inversely with square of the reinforcement size. Composite layers with higher H/ E have smaller accumulative strain, smaller accumulative strain energy, and thus better wear resistance. The wear mechanism was oxidation at low-applied load levels and adhesion/delamination at high-applied load levels.

Mechanical Properties of SiC<sub>p</sub>/Cu Composites Prepared by Electric Conduction Sintering

SiCp/Cu composites were fabricated at 700 oC and under 40MPa for 10min in vacuum by electric conduction sintering. The mechanical properties and microstructure of the composites were studied. The porosity of the composites increases when the volume fraction of SiCp exceeds 35%. The flexural strength of the composites decreases with increasing fraction of SiCp. The composites with 10 vol.% SiCp exhibited ductile fracture behavior, while composites with the volume fraction of SiCp in the range of 20–65% exhibited brittle fracture behavior. The composites with 35 vol.% SiCp showed the highest hardness.

Studies on machinability of Al/Sip + SiCp composite materials

This paper presents the experimental results on the machinability of silicon and silicon carbide particles (SiCp) reinforced aluminium matrix composites (Al/Sip + SiCp) during milling process using a carbide tool. The total volume fraction of the reinforcements is 65 vol%. The milling forces, flank wear of the tool and the machined surface quality of composites with different volume fraction of SiCp were measured during experiments. The machined surfaces of composites were examined through SEM. The results showed that the flexural strength and Vickers hardness are improved when certain volume fraction of silicon particles are replaced by silicon carbide particles with the same volume fraction and particle size and the effect of SiCp on machinability is optimal when 9 vol% silicon particles in Al/Sip was replaced by silicon carbide particles with the same volume fraction and the same particle size. Cracks and pits were found on the machined surfaces of composites due to the intrinsic brittleness of silicon particles.

Dependence of particle volume fraction on sound velocity and attenuation of EPDM composites

The sound velocity and the attenuation coefficient of EPDM (Ethylene–propylene Diene Monomer) composites incorporated with Silicon Carbide particles (SiCp’s) of various volume fractions (0–40%) were experimentally and theoretically investigated. For the experiment a through-transmission technique was used. For the theoretical prediction, some mechanical property models such as Reuss model and Coherent Potential Approximation (CPA) model etc. were employed. The experimental results showed that the sound velocity decreased with the increase of the SiCp volume fraction up to 30% and then increased with the 40 vol% specimen. The attenuation coefficient was increased with the increasing SiCp volume fractions. The modified Reuss model with a longitudinal elastic modulus predicted most well the experimental sound velocity and elastic modulus results.

Thermomechanical Properties of Functionally Graded Al-SiC<sub>p</sub> Composites

A theoretical model is applied to the analysis of thermomechanical properties of Al-SiCp FGMs in this study. Functionally graded Al-SiCp composites (Al-SiCp FGMs) consisted with 10 layers gradually changing volume fractions of Al and SiCp were fabricated using the pressureless infiltration technique. Al-SiCp FGMs plates of total thickness of 3mm, 5mm and 7mm with fairly uniform distribution and compositional gradient of SiCp reinforcement in the Al matrix throughout the thickness was successfully fabricated. The curvature of Al-SiCp FGM plates was measured to check the internal stress distribution predicted via a theoretical model for the analysis of thermomechanical deformation. The evolution of curvature and also internal stresses in response to temperature variations could be predicted for the different combinations of geometric thickness of FGM plates. Theoretical prediction of thermally induced stress distribution makes it possible to design FGM structures without any critical failure during the usage of them.

Fabrication, microstructure and properties of SiCp/Cu heat sink materials

Cu-coated powder was fabricated by electroless plating process, and the composition and morphology of coated powder were studied. Moreover, Cu-30, 40, 50 vol.% SiCp heat sink materials were fabricated by hot pressing using coated and uncoated powder. And the microstructure and thermophysical properties of the heat sink materials were also studied. The results show that SiCp particles distribute uniformly in heat sink materials and the interface between SiCp particles and Cu matrix is clear and well bonded. On the condition of same volume fraction of SiCp, the thermal conductivity of the material using coated powder is larger than that of the material using uncoated powder. Under experiment conditions, the thermal conductivity and coefficient of thermal expansion of Cu-30 vol.% SiCp heat sink material is 236.2 W.m −1.K −1 and 9.9 × 10 −6/K (30–200 °C) respectively. It provides important reference data for future experiments.

Correlation between tensile strength, elastic modulus and macrohardness in silicon carbide particle reinforced aluminium alloy matrix composites

In the present study, the correlation between the ultimate tensile strength, elastic modulus and macrohardness (HRB) in SiCp/Al composites has been investigated. The results indicate that the macrohardness test can be used to estimate qualitatively the ultimate tensile strength and elastic modulus of composites with different volume fractions of SiCp, as their correlation is approximately linear. However, the correlation between the ultimate tensile strength, elastic modulus and macrohardness of composites with different sizes of SiCp is complex, and as a consequence, the macrohardness test can slightly underestimate the elastic modulus and significantly overestimate the tensile strength.

The microstructure and the thermal expansion characteristics of Cu/SiCp composites

Copper/silicon carbide composites (Cu/SiCp) were made by the powder metallurgy method. Electroless plating was employed to deposit a copper film on SiCp powder before mixing with Cu powder in order to improve the bonding status between Cu and SiC particles during sintering. Thermal expansion property of as-formed product was measured in the temperature range from 50 to 550°C. The results showed that copper coating on silicon carbide particles could render uniform distribution of SiCp in the copper matrix. The composites exhibited positive thermal hysteresis behavior when cooled down from the peak temperature to room temperature, which can be explained in terms of the residual stresses and the interfacial bonding between copper and silicon carbide. The magnitude of this strain was a function of the SiCp volume fraction and the number of thermal cycles. The thermal expansion property of composites was measured and compared with those predicted from various theoretical models.

A study of the strength of P/M 6061Al and composites during high strain rate superplastic deformation

Metal Matrix Composites (MMCs) are potential candidate materials in the aerospace and automobile industries because of its attractive properties, in particular, their high specific properties, and Superplastic forming (SPF) is a good solution to the problems in the forming process of MMCs due to their low ductility resulting from the incorporation of reinforcement. High strain rate superplasticity (HSRS) is attractive for industrial applications because superplastic forming at high strain rates can reduce forming time greatly. The strength of P/M 6061 Al and 6061 Al/SiCp (3 μm) composites during superplastic deformation at temperatures of 853 K–871 K and a high strain rate of 0.1 s−1 has been studied in this paper. Experimental results presented a softening effect by the SiCp reinforcement. Mechanical and microstructural analyses show that the decrease in the strength during high strain rate superlastic (HSRS) deformation is associated with the decreased grain size of the Al matrix with increase of the SiCp volume fraction or the extrusion ratio, and the occurrence of liquid phase. The formation of the liquid phase was related to segregation of the solute atom during HSRS deformation.

Studies on microyield behavior of SiCp/2024Al composite materials

Microyield behavior of silicon carbide particles reinforced 2024 aluminum alloy (SiCp/2024Al composites) with three volume fractions of SiCp were investigated in this paper. The results of the studies showed that the composites exhibited some types of notable strain relaxation before microyielding when subjected to an applied stress far lower than conventional yielding stress. The microyield mechanism did not conform to the classical linear relation between the applied stress (σ) and square root of plastic strain (εp ½), proposed by Brown and Lukens. Microyield strength could be strongly affected by heat treatment routes. The thermal processing with large temperature change, such as high temperature quenching or annealing, rapid cooling to liquid nitrogen temperature, thermal cycling with large upper-lower cyclic temperature interval, etc., would lead to deterioration of microyield strength, whereas an appropriate aging treatment would significantly increase microyield strength of the SiCp/2024Al composites. TEM and X-ray diffraction analyses revealed the relationship between microyield behavior and microstructures. In general, dispersed strengthening phase S′, lower residual stresses and lower population of movable dislocations would be beneficial to microyield strength of the SiCp/2024Al composite materials. The effect of SiCp on microyield strength was dependent to thermal processing history.

Fabrication process and thermal properties of SiCp/Al metal matrix composites for electronic packaging applications

The fabrication process and thermal properties of 50–71 vol% SiCp/Al metal matrix composites (MMCs) for electronic packaging applications have been investigated. The preforms consisted with 50–71 vol% SiC particles were fabricated by the ball milling and pressing method. The SiC particles were mixed with SiO2 as an inorganic binder, and cationic starch as a organic binder in distilled water. The mixtures were consolidated in a mold by pressing and dried in two step process, followed by calcination at 1100 °C. The SiCp/Al composites were fabricated by the infiltration of Al melt into SiC preforms using squeeze casting process. The thermal conductivity ranged 120–177 W/mK and coefficient of thermal expansion ranged 6–10 × 10−6/K were obtained in 50–71 vol% SiCp/Al MMCs. The thermal conductivity of SiCp/Al composite decreased with increasing volume fraction of SiCp and with increasing the amount of inorganic binder. The coefficient of thermal expansion of SiCp/Al composite decreased with increasing volume fraction of SiCp, while thermal conductivity was insensitive to the amount of inorganic binder. The experimental values of the coefficient of thermal expansion and thermal conductivity were in good agreement with the calculated coefficient of thermal expansion based on Turner's model and the calculated thermal conductivity based on Maxwell's model.

The effects of SiC particle volume fraction on the microstructure and hot workability of SiCp/AA 2024 composites

The hot workability of AA 2024 composites reinforced with different volume fractions (5, 10, 15, 20, and 30 vol%) of SiCp was investigated within the temperature range 320–500°C at a strain-rate of 1.0 s −1. Dynamic recrystallization (DRX) or dynamic recovery (DRV) of the composites was studied from the flow curves and deformed microstructures. The effect of the SiCp volume fraction on the critical strain for the onset of DRX was analyzed from the relationship between the work-hardening rate and effective strain during hot deformation. The addition of the SiCp to an AA 2024 matrix alloy increased the dislocation density, resulting in a high flow stress and a low critical strain for the DRX of the composites. Upon increasing the SiCp volume fraction, the flow stress and the temperature showing the highest failure strain increased. Also, the difference in flow stress amongst the composites decreased with increasing deformation temperature. This result has been discussed in relation to dislocation density and stacking fault in the matrix of the composites.

Effect of Deformation and Ceramic Reinforcement on Work Hardening Behaviour of Hot Extruded 2124 Al-SiCp Metal Matrix Composites

Work hardening behaviour of discontinuously reinforced metal matrix composites (MMCs) is a complex phenomenon as compared to monolithic materials and is still not explicitly understood. Under the present investigation, the effect of deformation and reinforcement content on work hardening behaviour of extruded 2124 Al/SiCp MMCs has been reported. These MMC extruded rods having 10%, 15% and 20% volume fraction of SiCp and extruded at 9:1, 36:1 and 56:1 extrusion ratios (ERs) were used. Work hardening rates were calculated from true stress-strain data obtained from tensile testing results of these MMCs. The variation in work hardening rates was correlated with the variation of SiCp content and deformation (i.e., ER). Fracture strains were estimated using a model and correlated with the experimentally measured values. Morphology of fractured surfaces was examined to elucidate the different microstructural features induced during testing and their correlation with elongation.

The effect of cold rolling on the dynamic mechanical responses of SiCp/Al composites

Abstract The effect of cold rolling reduction on the dynamic mechanical responses of a 14 vol.% 3.5 μm SiCp/2024 Al and an 18 vol.% 3.5 μm SiCp/2048 Al were measured with a dynamic mechanical analyzer. It was found that both the elastic modulus and the damping capacity were not sensitive to the amount of cold rolling for both composites. Whilst little change was observed in the 14 vol.% SiCp reinforced composite, in the 18 vol.% SiCp reinforced composite the elastic modulus decreased and the damping capacity increased slightly as the amount of cold rolling was increased. The results suggest that a small SiC particle size and a suitable volume fraction of SiCp, together with a good SiC–Al interfacial bonding can minimize the amount of SiC particle fracture and SiC–Al interfacial debonding upon cold rolling. Control of these defects is the major reason for the insensitivity of the elastic modulus and damping capacity upon cold rolling.

Low volume fraction SiCp/AA 380.0 composites fabricated by vacuum infiltration

A vacuum infiltration process has been developed to fabricate the aluminum matrix composites reinforced with low volume fraction (<50 vol%) of SiCp. Generally, it is difficult to fabricate low volume fraction particulate composites by traditional infiltration processes because the particles always pack up to about 50 vol% in the preforms or compacts. In this study, the powder compacts were prepared of the well-mixed Ni-coated SiCp and pure aluminum powders and then were packed in quartz tubes. An aluminum alloy (Al–8.7% Si–2.6% Cu) with a composition similar to AA 380.0 was used to infiltrate these compacts. Experimental results showed that the infiltration temperature of 640 °C is favorable for the fabrication of these composites. Infiltration behavior, microstructure, nickel distribution, bending test, and fractography of the composites were investigated.

Effects of SiCp reinforcement by electroless copper plating on properties of Cu/SiCp composites

Silicon carbide reinforced copper matrix composites containing 50–80 vol.-%SiCp were fabricated by hot pressing copper coated SiCp powder. The results show that the densification, thermal expansion coefficients, flexural strength, and thermal conductivity of Cu/SiCp composites reinforced by electroless copper plating and their corrosion resistance in 5%NaCl solution are better than those without electroless plating. Physical properties and flexural strength of the composites decrease with an increase in SiCp content, whereas the corrosion resistance increases with an increase in SiCp volume fraction. By observing the fracture surface after a flexural test, it can be seen there are two types of fracture model: the cracking of Cu/SiCp interface and the pulling out of SiCp particles. The experiment also proved that the bonding strength of the Cu/SiCp interface and the pressure of the hot pressing operation are the two main factors which influence the fracture of these composites.

Multiple NDE Techniques for the Measurement of Constituent Volume Fractions in Metal Matrix Composites

Multiple nondestructive evaluation (NDE) techniques are developed for determining the constituent volume fractions of silicon carbide particulate (SiCp) reinforced aluminum (Al) matrix composites. The composite constituents studied include SiCp reinforcement and intermetallic compounds formed during the processing stage. The proposed techniques employ measurements of ultrasonic velocity and eddy current conductivity, together with theoretical models that relate the effective anisotropic properties of the composites to their microstructures. The SiCp volume fraction is calculated first by coupling the measured velocity with the two-phase (SiCp and Al matrix) model prediction. The intermetallics concentration then is calculated using the three-phase (SiCp, intermetallics and Al matrix) model with the measured conductivity. The methods are shown to be reliable in determining the volume fractions of the reinforcement and the intermetallic phase. The techniques may be adopted in a production unit for the quality assessment of the metal matrix particulate composite extrusions.