Wettability Of SiC Research Articles

Wetting of SiC by molten Cu–20Me–2Cr (Me=Ag, Mn, Si, and Sn) alloys at 1373 K

Abstract In this work, the effect of the third addition (Ag, Mn, Si, and Sn) on the wettability and the interfacial structures of Cu–20Me–2Cr/SiC systems was investigated. The third addition Me has the obvious effect on the wettability and the spreading dynamics. The sequence of effectiveness is Sn > Ag > Mn > Si. Si Addition can suppress the precipitation of the wettable reaction products, and thus that caused the poor wettability. Although additions of Ag and Mn can improve the wettability significantly, a dissolution zone beneath the reaction layer would be formed. When the third addition Me was thermodynamically repulsive with Si. Meanwhile, the critical concentration of Si in liquid for equilibrium with SiC was less than the corresponding amount of graphite consumed by Cr addition. The dissolution zone would be suppressed. Sn addition satisfied this situation, and thus the best wettability can be achieved. The spreading of Cu–20Me–2Cr/SiC was controlled by the decomposition of SiC rather than the precipitation reaction.

Studies on microstructure and mechanical characteristics of as cast AA6061/SiC/fly ash hybrid AMCs produced by stir casting

Fly ash has been receiving the extensive concentration as a strong reinforcing element for Aluminum Matrix Composites (AMCs) to strengthen the properties and cut the price of manufacturing. AA6061 reinforced with various weight percentages of fly ash particulates and a constant weight percentage of SiC were prepared by stir casting technique as it is one of the simplest and cost-effective method for producing AMCs. Wettability of SiC and Fly ash particles with the aluminum was enhanced by fly ash itself. The microstructure, hardness and tensile properties of manufactured AMCs were analyzed. Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) discovered a harmonized dispersion of SiC and fly ash particles with superior bonding with the matrix material. The inclusion of fly ash particles in to aluminum matrix enhanced the microhardness and Ultimate Tensile Strength (UTS) of the AMCs.

Roles of alloying elements in wetting of SiC by Al

Wetting of SiC by Al alloys is a key issue in the preparation of SiC-reinforced Al matrix composites. The wettability could be improved by alloying of Al, yet controversial results widely exist in the literature. We investigated the effects of four important alloying elements (Si, Cu, Ti and Mg) and their concentrations on the wettability in the Al/SiC system using a dispensed sessile-drop method. The results demonstrate that Si could weaken or even inhibit the formation of Al4C3 and substantially improve the wettability via an adsorption effect; Cu slightly deteriorates the wettability, but alleviates the formation of Al4C3 by decreasing the activity of Al; Ti strongly adsorbs at the solid−liquid interface, forming TiCx instead of Al4C3, and thus significantly improves the wettability; Mg may also favor the wettability due to its help in the disruption of the oxide film covering the Al surface via evaporation and its strong affinity for the silica film on the SiC surface; but for a clean Al/SiC system, the effect of Mg is essentially limited. In addition, the evaporation of Mg always leads to a reduction in the drop volume, which causes a decrease in the apparent contact angle, but this effect is usually neglected.

Mechanical Properties of Nano SiC-Reinforced Aluminum A356 Fabricated by Stir Casting Method

Nano SiC-reinforced aluminumA356 (A356/SiC) has been successfully fabricated using stir casting method. The specimen was fabricated by adding various Nano SiC concentrations, i.e. 0, 0.10, 0.15, 0.20, 0.25, and 0.30 wt.%, at fix 1 wt.% magnesium into aluminum A356 melt. After stirring at certain time, the mixture was poured into the mold that has been preheated at 350oC for 5 minutes. The mechanical properties were characterized using tensile, hardness, and wear testing, where as the microstructural observation was performed using an optical microscope. The results show that the mechanical properties were optimum at 0.25 wt.% Nano SiC with a strength of 175.57 MPa (21.87%), toughness of 0.0287 Joules/mm3(14.8%), hardness of 56.54 HBN (50%), and wear resistance of 1.75 x 10-5 mm3/mm (21.13%). These results indicate that the fabrication approach was successful in producing cast MMCs samples and the use of Nano SiC and Magnesium as a wetting agent with continuous stirring were found to promote the wettability of SiC and A356 matrix alloy and thus result in reasonable mechanical properties of the composite.

Wetting of SiC by Al-Ti alloys and joining by in-situ formation of interfacial Ti3Si(Al)C2

Two pressureless and reliable procedures for brazing SiC-based materials have been designed. The joining was obtained by the in-situ formation of a Ti3Si(Al)C2 MAX phase using simple Al-Ti interlayers. Wettability studies were conducted using several Al-Ti alloys in contact with SiC at 1500 °C. The interfacial microstructures and thermodynamic analysis demonstrated that liquid Al3Ti in contact with SiC formed a well-bonded Ti3Si(Al)C2 interfacial layer. These findings guided the design of two joining methods: one consisted of the simple infiltration of Al3Ti into the brazing seam, while an Al3Ti paste/Ti/Al3Ti paste interlayer assembly was designed for the second process. Sound interfaces without cracks were obtained in both processes. The average shear strength was very high, 296 MPa, for the infiltration method; the drawback was the presence of residual Al. Joining through Al3Ti/Ti/Al3Ti interlayers avoided the presence of low-temperature melting phases, with lower shear strength: 85 or 89 MPa depending on the testing method.

Effects of Cu content on the wettability of SiC with Al-Ti-Si-xCu alloy and bending strength of resulting SiC matrix composite

The effects of the addition of Cu in an Al-Ti-Si alloy on the wettability of the ceramic SiC with respect to the resulting Al-Ti-Si-xCu alloy as well as the bending strength of the resulting composite were investigated. The melting point of the Al-Ti-Si-xCu alloy decreased with an increase in the Cu content, which facilitated the diffusion of the alloying elements. The first and second stages of the wetting process were promoted. The contact angles of 0Cu, 5Cu, and 10Cu after heating at 900°C for 10min were 102°, 90° and 89°, respectively. However, after 210min, they were similar at approximately 40°, as no new phases were formed at the interface. In addition, the three-point bending strength of the infiltrated SiC ceramic samples was almost twice that of the original one. As the Cu content was increased from 0 to 10wt%, the relative volume fraction of Ti3Si(Al)C2 increased. However, for a Cu content of 10wt%, the bonding rate between Al and SiC decreased. Therefore, the three-point bending strength of the infiltrated composite was the highest at 433MPa in the case of the sample infiltrated with the 5Cu alloy at 900°C for 6h.

Wettability of SiC and graphite by Co–Ta alloys: evaluation of the reactivity supported by thermodynamic calculations

Within the context of the design of high-temperature brazing process for C and SiC-based composites, a basic study is presented here about the wetting and interfacial reactivity of Co–Ta alloys in contact with graphite or SiC. Wetting results are presented for the first time showing that Co–Ta alloys wet C or SiC fairly or excellently depending on the relative amount of Ta. The final interfacial microchemistry and microstructures are the result of the interplay between the typical interfacial phenomena of the pure elements. Specifically, depending on the alloy composition, dissolution of the ceramic phase by Co or formation of a continuous interfacial layer of TaC that prevents dissolution prevails. The discussion about the interfacial reactivity between liquid Co–Ta alloys and graphite or SiC, as well as the interpretation of solidification phenomena and the formation of interfacial phases, is supported by making reference to new multi-component phase diagrams calculated by CALPHAD method.

The Effect of Mg on the Wetting Behavior of SiC-Al System

The wetting behavior of SiC by molten Al and Al-Mg alloys using the sessile-drop testing equipment was investigated. The results showed that Mg has a remarkable influence on the wettability and reaction in the Al/SiC system. The contact angle between SiC substrate and molten Al-Mg alloys decreased more quickly with increasing of Mg content. The transition temperature from non-wetting to wetting dropped with increasing of Mg content, suggesting that the addition of Mg does promote the wettability of SiC by molten Al. The role of the Mg addition on the wetting was presumably attributed to its deoxidation as well as the inhibition of the interfacial reaction between Al and SiC.

Preparation of Al6061-SiC with Neem Leaf Ash in AMMC’s by Using Stir Casting Method and Evaluation of Mechanical, Wear Properties and Investigation on Microstructures

Aluminum Metal Matrix Composites (AMMCs) are promising materials for advanced structural, aviation, aerospace, marine, defense applications, automotive and other related sectors because of their excellent combination of properties. The AMMCs is fabricated by using stir casting method, which is the simplest way of fabricating a material. In this paper aluminium alloy 6061 is been reinforced with SiC along with fly ash and neem leaf ash. The three samples have been fabricated they are Sample1 (Al85%+SiC15%), Sample2 (Al 85%+SiC5%+FlyAsh10%) & Sample3 (Al85% +SiC5%+ Neem leaf ash10%). After fabricating this three sample the following test are conducted like Hardness test, Microstructure Test, Friction and Wear Test. The wettability of SiC and Neem leaf ash particles in the matrix was improved by adding them. The optical and scanning electron micrographs showed a homogeneous dispersion of composition material. The result shows that the Sample-3 (Al80% +SiC10%+ Neem leaf ash10%) shows improvement in mechanical properties like hardness, the wear properties has been reduced and their Micro structural characterization clearly shows uniform distribution of SiC and Neem Leaf ash in the composition.

Study on the SiC-Al Co-Continuous Phase Composites

SiC/Al co-continuous phase composites were fabricated by pressureless infiltration technology with reticulated silicon carbide porous ceramics as matrix and aluminum or magnesium as reinforcement phase. The effect of magnesium addition and holding time on the relative density, mechanical properties and macro morphology of the composites was investigated. The results showed that the porosity of SiC/Al co-continuous phase composites decreased with the increase of the holding time. The wettability of SiC and Al was improved with the addition of Mg. The hardness of SiC/Al co-continuous phase composites increased with the increase of the holding time. SiC and Al combined closely at longer holding time.

Synthesis and Characterization of Al6061-Fly Ashp-SiCp Composites by Stir Casting and Compocasting Methods

Stir casting is one of the simplest ways of producing aluminum matrix composites (AMCs). This work focuses on the fabrication of AMCs reinforced with various weight percentages of SiC particulates and a constant weight percentage of Fly Ash by modified stir casting route. The wettability of SiC and Fly ash particles in the matrix was improved by adding magnesium into the melt. The microstructure and mechanical properties of the fabricated AMCs were analyzed. The optical and scanning electron micrographs revealed a homogeneous dispersion of both SiC and Fly ash particles in the aluminum matrix. The SEM micrographs revealed that the addition of Fly Ash helped to prevent SiCp dissolution and the formation of Al4C3. The mechanical properties like hardness and tensile strength were improved with the increase in weight percentage of SiC particulates with constant weight percentage of Fly Ash in the aluminum matrix.

Effect of Mg Content on the Characteristics of Al/SiC Nanocomposite Powders Produced via <i>In Situ</i> Powder Metallurgy Method

In the present study the effect of Mg addition on the characteristics of Al/SiC nanocomposite powder particles produced via a relatively new method called in situ powder metallurgy (IPM) is investigated. Commercially pure Al and Al-Mg alloy melts containing different amounts of Mg were used as the matrix alloy. Nano-sized SiC particles with the average size of 60 nm were used as the reinforcing material. The effect of Mg content on the fluidity of the melt as an influencing factor affecting both the process yield and wettability of SiC with molten metal was investigated. The size distribution of produced powders was characterized using a laser particle size analyzer. Scanning electron microscopy was utilized to investigate the possibility of embedding of SiC nanoparticles within the metallic matrix. Results of microhardness measurements together with SEM micrographs and EDS analysis showed that nano-sized SiC particles could be embedded in the relatively coarse Al-Mg powders containing at least 1 wt.% Mg.

Survey on wetting of SiC by molten metals

Abstract Good wetting and low reactivity of metal/ceramic couples are key factors in many technological processes, in particular in metal/ceramic joining, to avoid degradation of ceramics and to achieve the desired properties during service. Silicon carbide is a covalent material of great technological interest due to its excellent overall properties. Starting from a survey of the surface energies of SiC and liquid metals, the reactivity and wettability of pure metal/SiC systems, as well as the wetting behavior and mechanisms of (liquid metal + Si)/SiC systems are reviewed for understanding the interfacial bonding and for supporting the development of application-oriented processes like non-reactive brazing. Silicon chemisorption and interactions between the molten alloys and SiC at the metal/substrate interface and the intrinsic properties of the alloys or of the pure metals are considered to play the key roles in interfacial bonding. In particular, additions of Si can limit or even suppress the substrate dissolution leaving the solid–liquid interface nearly undisturbed. At the same time, oxidation–deoxidation processes at the SiC surface are the basic mechanisms to be controlled in order to allow the liquid phases to contact a “pure” SiC surface. The need of further investigations, covering basic interfacial phenomena including both experiments and ab-initio modeling of the solid–liquid interfaces is strongly underlined.

Wettability of SiC and alumina particles by liquid Bi under liquid Al

In this paper a new experimental method to measure contact angle of liquid metals on solid particles under an immiscible second liquid metal is described. This includes efficient mixing of the three-phase system (two immiscible liquid metals with solid dispersed particles) with subsequent solidification. The micrographs of the cross sections of samples are analyzed for the distribution of the particles between the bulk of the two metals and the interface between them. As an alternative, exact positions of the particles can be measured at the interface between the two solidified metals. These two measurements are used to estimate the contact angle of one liquid metal on the solid particles under another, immiscible liquid metal. As an example, contact angle of a liquid Bi-rich alloy on SiC and alumina particles is measured under liquid Al-rich alloy. The liquid Bi-rich alloy was found to wet perfectly (with zero contact angle) alumina particles under liquid Al-rich alloy, while the contact angle on SiC is found to be around 88°. These contact angle data are shown to be relevant to control the stability of liquid metallic emulsions formed between the two immiscible liquid metals stabilized by the solid particles.

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.

Influence of oxygen partial pressure on the wetting of SiC by a Co–Si alloy

In this investigation the influence of oxygen partial pressure P O 2 on the wetting of SiC by a Co–Si alloy was studied. Wetting experiments were carried out in argon with different oxygen contents (from 5 to 1000 ppm). The relationship between wetting and deoxidation of surfaces (SiC and Co–Si alloy) was investigated. Calculations were performed to evaluate the temperature range over which deoxidation is possible. These calculations are in agreement with the experimental results.

The wettability of SiC ceramics by molten E 2O 3(ss)/AlN (E 2O 3(ss) = solid solution of rare earth oxides)

Wetting of SiC by molten E 2O 3(ss)/AlN as a function of temperature up to 2000 °C was investigated under argon and nitrogen atmospheres. E 2O 3(ss) is a solid solution of rare earth oxides produced from xenotime by hydrometallurgy. Wetting was evaluated from contact angle measurements using the sessile drop method. Contact angle was around zero under argon atmosphere, but could not be measured under nitrogen atmosphere, due to bubble formation. The interfaces between molten E 2O 3(ss)/AlN and SiC were analysed by scanning electron microscope (SEM) and X-ray diffraction (XRD).

Study of the Effects of the Atmosphere on the Wettability of SiC by Copper Alloys

Ceramic-metal composite materials (CMC) are a new technology based on present and future applications with a wide range of possible material combinations. CMC materials combine the positive features of ceramics with the toughness and ductility of metallic phases. The development of these materials will extend the application field of structural ceramics up to work temperatures limited by the melting point of the metallic phase. The main step to define compatibility between CMC materials is to determine their physical and chemical interaction mechanisms. The main aim of this work is to evaluate the silicon carbide - copper based alloy system for developing CMC materials. The contact angle between Cu and SiC at 1100°C is 140° and the bonding is weak; furthermore, investigations have shown that wettability is improved with Ti additions. Two Cu based alloys containing 3 and 5 wt% of Ti were used in this work. Wettability was evaluated by the sessile drop method in a vacuum and argon atmosphere at a test temperature of 1200°C. The specimens obtained were subsequently characterised by Scanning Electron Microscopy, EDX, DRX and DTA Analysis in order to study the type of interface developed after such treatment. The most important results are related to the differences between atmospheres and Ti diffusion.

On enhancing the interfacial chemistry of a simulated AA2014-SiCp composite material

The use of aluminum alloys in automotive applications has increased significantly in recent years due to the need for more fuel-efficient vehicles. These alloys alone do not enjoy the strength offered by traditional ferrous products. However, the development of new alloys through micro/macroalloying and the incorporation of load-bearing materials such as SiC into the matrix have enhanced their popularity. Unfortunately metal matrix composites such as AA2014-SiC often fail catastrophically due to fibre or particulate pullout in service. Such failures are difficult to predict and are often a result of poor wetting at the metal/reinforcement interface. In the present work Sn and Ni were examined as potential sintering/wetting aids. In particular, Sn or Ni (0.5–2 w%) were added to a simulated AA2014 alloy (Al-4Cu-0.5Mg) with and without 14.5 w% SiC following standard powder metallurgy techniques. Because the distribution of blend constituents is of critical importance various dispersants were evaluated. Best particle dispersion was obtained using oleic acid while mixing for 8 h. Sintering temperatures ranged from 605–620°C and both green and final densities were determined using mercury densitometry. Resulting microstructures were examined using scanning electron microscopy and electron probe microanalysis with particular attention directed to the SiC-alloy interface. Nickel was found to enhance the wetting of SiC by AA2014 and the interfacial region was found to be chemically superior to a commercial copper-coated SiC product. Tin contributed to an increase in intermetallic formation. It is believed that the improved interfacial region was due to the presence of a small amount of liquid phase at the AA2014-SiC interface giving a chemical rather than the usual mechanical bond between reinforcement and alloy.

The infiltration of cobalt silicides into silicon carbide preforms

The wettability of SiC by cobalt silicide, Co saturated and Ti doped cobalt silicide was investigated by measuring the contact angles and calculating the surface tensions in order to access the possibility of using them to form CoSi SiC composites by cobalt silicide infiltration. Spontaneous infiltration of SiC powder preforms was accomplished at 1600 °C. The infltration process is analysed. The microhardness and fracture toughness of the infiltrated samples were measured and are reported.