Introduction Of SiC Particles Research Articles

Microstructure and properties of SiC ceramic-modified aluminium alloy fabricated using wire arc additive manufacturing

A method for improving the properties of the deposited metal in wire arc additive manufacturing of Al–Si alloy is proposed here, which introduces SiC ceramic particles into the side-axis wire feed. The effects of SiC ceramic particles on the macroscopic morphology, microstructure and mechanical properties, corrosion resistance, and wear resistance of deposited metals were studied. The results show that the introduction of SiC particles will not affect the surface-forming quality of the deposited metal; this is likely due to the stable droplet transfer and no splashing. The transverse and longitudinal tensile strengths are increased by 10.1 % and 11.3 %, respectively, while the corresponding elongations are increased by 33.1 % and 47.2 %, respectively. Further, the corrosion resistance and wear resistance of Al–Si alloy deposited metals containing SiC are improved. The (100) base surface has strong texture characteristics along the deposition direction X0, and the maximum polar density decreases to 13.63, which indicates that SiC promotes the transformation of columnar crystals to equiaxial crystals. The interface between SiC and Al is non-coherent, and the performance improvement lies in the enhanced dispersion distribution and load transfer of SiC. A ring structure was prepared using double-wire arc additive manufacturing technology, and the feasibility of side-axis wire feeding technology was verified.

Nucleation and growth mechanism of Ni/SiC composite coatings electrodeposited with micro- and nano-SiC particles

To study the nucleation and growth mechanism of Ni/SiC composite coatings, electrodeposition was conducted in the Ni bath containing SiC particles with different sizes. Compared to the Ni coating electrodeposited from the bare Ni bath, the Ni/SiC composite coatings exhibited similar grain size but rougher surface morphology due to the incorporation of SiC particles. By means of chronoamperometry (CA) and linear sweep voltammetry (LSV) techniques, it was found that the introduction of SiC particles did not change the nucleation mode of Ni: the Scharifker-Hills three-dimensional instantaneous nucleation mode. However, the nucleation sites on the cathode were reduced due to the inert surface and low conductivity of SiC particles. At a step potential of −0.94 V, Ni presented the maximum nucleation density (N0) of 3.09 × 107 cm−2, which was reduced by one order of magnitude for the Ni/SiC. Furthermore, SiC particles in the bath would extend the diffusion path of Ni2+ ions, resulting in the decrease in diffusion coefficient from 1.04 × 10−7 cm2 s−1 (Ni) to 9.91 × 10−9 cm2 s−1 (Ni/50 nm SiC), 1.83 × 10−8 cm2 s−1 (Ni/500 nm SiC) and 2.29 × 10−8 cm2 s−1 (Ni/5 μm SiC), suggesting the “Blocking effect”. COMSOL simulation further confirmed the “Blocking effect”. The “Blocking effect” would lead to excessive interface gaps around 5 μm SiC particles due to the uneven electrodeposition of Ni. To address the issue, we proposed that adding non-ionic surfactants into the bath to lower the electrochemical reaction rate of Ni2+ ions and accordingly gained composite coatings with fine continuity.

Effect of multi-groove reinforcement strategy on Cu/SiC surface composite fabricated by friction stir processing

In the present study, Cu/SiC surface composite was fabricated by friction stir processing (FSP) via multi-groove technique eyeing to improve SiC dispersion in copper matrix and hence improving mechanical and tribological behaviour. Microstructural features revealed more uniform dispersion of SiC particles in copper matrix when fabricated through multi-groove technique (MGT) as compared to single groove technique (SGT). The interface between copper matrix and SiC particles were clean without any obstruction/interruption in the form of voids or pores or intermediate phases formed which indicated excellent interfacial bonding. Furthermore, the obtained microstructure revealed drastic grain refinement in FSPed copper without reinforcement and the composites fabricated through SGT and MGT and the reduction in grain size was more for the composites fabricated by MGT. Tensile tests revealed incremental behaviour over strength with increase in number of grooves although it was far less as compared to base copper. Fractured surfaces of composites fabricated by both techniques (SGT and MGT) indicated reduction in ductility. However, results obtained for FSPed copper without reinforcement showed higher strength and ductility as compared to base copper. It was also demonstrated that incorporation of SiC particles in copper matrix improved hardness and wear resistance and it further enhanced with increased number of grooves. The wear mechanism changed with introduction of SiC particles in copper matrix and was supposed to be because of reduction in friction coefficient.

Enhancing stab resistance of thermoset–aramid composite fabrics by coating with SiC particles

Aramid has been proved to have excellent ability to protect against ballistic threats however, it has poor puncture resistance. In this research, flexible fabric materials with outstanding stab resistance were prepared with thermoset–aramid composites coated with SiC particles. The stab resistance and mechanical properties of the flexible fabric composites were evaluated. Results showed that the stab resistance of the thermoset–aramid fabrics was effectively improved by the introduction of SiC particles; however, the tear force was slightly decreased. Composites coated with 20 wt.% SiC particles exhibited the best stab resistance against knife cut. Scanning electron microscopy observation showed that the irregular SiC particles were embedded into the gaps among aramid fibers. The increased stab resistance was ascribed to the fact that the introduced SiC particles with hard and refractory nature could highly enhance the fiber-to-fiber friction and blunt the sharp metal blade by abrasion.

Preparation and characterization of SiCp/2024Al composite foams by powder metallurgy

SiCp/2024Al composite foams were manufactured by powder metallurgical methods using foaming agent CaCO3 in order to enrich the foam fabrication process and promote its development and extensive application. The effects of CaCO3 and SiC volume fractions on the foaming behaviours were investigated by means of SEM and Magiscan-2A image analysis technique. The influence of SiC content on the compressive behaviour was analyzed using Gleeble 1500 thermal simulation testing machine. The experimental results show that with increasing the foaming agent, the porosity and pore dimension increase first and decrease later. With increasing the reinforcement content, the porosity and pore dimension decrease. The compressive curves reveal that the introduction of SiC particles can improve compressive yield strength and energy absorption capacity. Meanwhile, it is found that SiCp/2024Al composite foams are the brittle foam materials.

The Fabrication of Titanium Aluminide Matrix Composite Sheet by Rolling and Reaction Annealing

In this work, Ti5Si3 and TiC particle reinforced titanium aluminide matrix composite sheet was fabricated by rolling and reaction annealing using the starting materials of SiCp/Al composite and pure titanium sheet. The deformation compatibility of both starting materials and microstructure evolution during reaction synthesis were studied. The results show that titanium has the similar deformability with SiCp/Al composite via the introduction of SiC particles and the selection of proper rolling temperature. Titanium aluminide matrix composite reinforced by Ti5Si3 and TiC was synthesized by reactions during the annealing. The reactions include the formation of titanium aluminide matrix by the diffusion synthesis between titanium and aluminum, as well as reinforcements (Ti5Si3 and TiC) by in-situ reaction between SiC and titanium.

Densification of Spray-Deposited 8009Al/SiCp Composite Tubular Billet

In the present investigation, SiC particles-reinforced 8009A1 matrix composite tubular billet was prepared by spray co-deposition and followed by a novel densification process, i.e., wedge pressing (WP). The densification behavior of the porous composite tubes has been discussed. The experimental results show that the composite is a coalesced bulk composed of deposited particles, reinforcements, and porosity. Composite exhibits a higher densification velocity at the early stage of compaction than that of monolithic alloy, whereas, at the end of compaction, the composite has lower relative density as compared with that of the matrix alloy due to the introduction of SiC particles. The microstructure and formability of the porous composites tubular billet can be effectively improved by the canning WP without forming cracks on surface and edge.

Enhancing wettability of SiC in semisolid A356 aluminium matrix composites

Stir casting plus cooling plate technique has been used for the fabrication of Al matrix composites based on alloy 356. Improvement of the wettability of SiC particles was carried out, employing the oxidisation of SiC particles, the use of wetting agents by adding magnesium into the matrix and the coating of SiC particles using a sol–gel technique. The introduction of SiC particles into partially solidified alloy with high viscosity prevents the particles from floating and agglomerating. Unoxidised SiC particles are mostly detached from the Al matrix during the grinding suggesting poor adhesion and poor wettability between the matrix and the particles. Oxidised SiC particles and sol–gel silica coated SiC particles indicate good binding between composite and matrix. The use of magnesium promoted wettability of SiC with A356 alloy. The eutectic silicon phase formed on the surface of SiC particles during solidification may be due to nucleation effects provided by the particles.

The Chemically Assisted Immersion of Ceramic Particles into Molten Al Alloy

In this work, the chemically assisted immersion of SiC, Si3N4, and Mg3N2 particles into a molten aluminum alloy was experimentally investigated for different processing times and temperatures. Before the introduction of SiC particles into the melt, their surface chemical composition was changed in various ways in order to promote exergonic interfacial reactions (i.e., the chemical reaction with ΔG<0) between the applied layers and the melt. In this way, the activation energy of the overall process of immersion was calculated for an interfacial reaction. Si3N4 and Mg3N2 were introduced into the melt as received. The investigation showed that the volume fraction of particles successfully immersed increases linearly with the time of immersion and exponentially with the temperature of the molten aluminum alloy. It was also evident that the volume fraction of ceramic reinforcement increases with lowering of the activation energy of the interfacial chemical reaction. In this way, the use of a interfacial reaction with a low activation energy routinely resulted in a composite with more than 20 vol% of ceramic particles dispersed in the melt. The calculated activation energy of the chemically assisted immersion corresponds to the activation energy of the interfacial reaction. Based on this, it is likely that the rate-limiting step in the overall process of chemically assisted immersion is probably determined by the kinetics of the interfacial reaction. A theoretical explanation of these findings is offered based on the general assumption that there is a contribution from the free energy released by the applied interfacial reaction to wetting behavior between the ceramic particles and the melt.

Stress-induced microstructural defects in a 15% SiC aluminium alloy metal-matrix composite

The introduction of SiC particles into an alloy matrix system will change the stress field within the matrix. Residual stresses will be introduced when the composites are undergoing temperature changes, cooling down during solidification and also when undergoing thermal treatments, due to the differences in the coefficient of thermal expansion (CTE) between the SiC particles and the alloy matrix. The substantial changes in the stress field surrounding the ceramic particles can affect diffusion processes and precipitation kinetics, and hence may have an effect on the microstructure, upon which the mechanical properties of the composite are strongly dependent. Previous studies [1, 2] have shown that the microstructure of a cast aluminium alloy matrix can be greatly modified by the presence of SiC particles, with a reduction of the primary aluminium grain size. A high dislocation density in the composite materials has been commonly observed in the microstructural studies of different composite systems [3-5], as a result of the reinforcements introduced. This increased dislocation density has been shown to have accelerated the ageing process of the material, but not necessarily to have increased the hardness levels [6]. The influence of the prior strain on precipitation in an aluminium alloy was investigated by Rack [7], who showed that its presence can have a marked influence on precipitation phenomena by changing the kinetics of both the diffusion and nucleation processes. Therefore, an understanding of the defects related to the reinforcement agents in composite materials becomes important with respect to an appreciation of their microstructural response. Thus, the objective of this study was to investigate the effects of SiC particle reinforcement and thermal treatment on the microstructure of the matrix of a cast aluminium alloy A356-15% SiC particle composite, with emphasis on the microstructural defects present in the material. The composite was an A356 aluminium alloy reinforced with 15 vol % /3-SIC particles which was fabricated using a standard sandcasting technique by Alcan. The nominal chemical composition of the composite was 6.99% Si, 0.34% Mg and 0.11% Fe. The thermal treatments employed for the composite were solution-treated at 540°C for 8h, waterquenched and then aged at 155 °C for various times. The microstructures of the composite were then examined using electron microscopy. Fig. 1 shows the microstructure of the as-cast SiC A356 alloy composite. One of the significant