Oxidation Of SiC Particles Research Articles

The oxidation of SiC particles and its interfacial characteristics in Al-matrix composite

The passive oxidation behavior of SiC particles has been studied in an electric furnace at atmospheric pressure and in dry air, the weight change due to the transformation from SiC into SiO2 is descibed as a function of exposed temperature and holding time. According to the oxidation data of SiC particles, the oxidation parameters and the degree of oxidation for SiC particles can be controlled. Controllable preoxidation of SiC particles is one of the keys for designing interface and interphase to achieve high performance aluminum composite. Consequently, the evolution of interfacial reaction products in 2014 aluminum alloy composite reinforced with oxidized-SiC particles after extended thermal exposure at elevated temperatures were further characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and X-ray diffraction. While it could act to prevent the interfacial reaction between SiC particles and aluminum alloy, the preoxidation of SiC particles led to the formation of other interfacial reaction products. The observation of the microstructure revealed that at elevated temperatures nano-MgO formed initially on the surface of the oxidized SiC particles and then turned into nano-MgAl2O4 crystal due to the reaction between the SiO2 and aluminum alloy containing Mg. TEM observations indicated that the oxidized layer on SiC particles was uniform and had a good bonding with SiC and aluminum alloy.

Oxidation-induced strengthening and toughening behavior in micro- and nano-composites of Y2O3/SiC system

Abstract Effects of oxidation on mechanical properties has been investigated for micro- and nano-composites of Y 2 O 3 –SiC systems. SiC particles with mean sizes of 5 μ m and 300 nm were dispersed in the former and latter material, respectively. The room temperature fracture strength and toughness increased after oxidation around 900–1000°C for both the composites; the nanocomposite showed much larger increases than the micro-composite. The microstructural observations and the residual stress measurements revealed that these improvements are mainly due to the surface compressive stress generated by the oxidized SiC particles.

Thermal expansion behavior of particulate metal-matrix composites

Aluminum-matrix composites containing thermally oxidized SiC particles of controlled diameter ranging from 3 to 40 μm have been produced successfully by vacuumassisted high-pressure infiltration. Their thermal-expansion coefficients (CTEs) were measured between 25 and 500 °C with a high-precision thermal mechanical analyser (TMA), and compared with the predictions of various theoretical models. The thermal-expansion behavior of the three-phase Al/SiC/SiO 2 composite shows no significant deviation from the predictions of elastic analysis, since the measured CTEs lie within the elastic bounds derived by Schapery's analysis. The effect of particle size is quite evident in the pressure-infiltrated composites: the larger the particles, the greater the thermal expansion of the composite. The observed behavior of these composites is discussed in terms of particle size, silica layer formed during oxidation, and thermal stresses developed as a result of the CTE mismatch between the reinforcement and the matrix.

Effect of thermomechanical processing on the microstructure and mechanical properties of Al [sbnd]Mg (5083)/SiCp and Al [sbnd]Mg (5083)/Al 2O 3p composites. Part 3: Fracture mechanisms of the composites

In this paper, the last of three articles, the fracture mechanisms of as-cast composites, extruded composites and extruded monolithic 5083 aluminum alloy deformed in uniaxial tension are discussed. Dimple fracture is observed in both the monolithic 5083 aluminum alloy and the extruded composites, whereas the fracture of the as-cast composites is mainly caused by decohesion at matrix/particle interfaces and crack propagation along dendrite boundaries. For extruded composites the fracture is mainly nucleated by particle cracking and final failure occurs by shear coalescence of the small void sheets of matrix between the large reinforcing particles (or between clusters of particles). The large voids caused by fracture/decohesion of reinforcing particles induce localization of deformation in the matrix which accelerates the nucleation, growth and coalescence of the small voids in the matrix. Localization of deformation is one of the important factors which decrease the ductility of the composites. Three types of composites reinforced by SiC particles, artificially oxidized SiC particles prior to their incorporation and Al 2O 3 particles are examined. The effects of the interfacial reactions on the fracture of the composites are also presented.

Effect of thermomechanical processing on the microstructure and mechanical properties of Al [sbnd]Mg (5083)/SiCp and Al [sbnd]Mg (5083)/Al 2O 3p composites. Part 2: Tensile properties at different temperatures

In this paper, the second part of our trilogy, the mechanical properties of as-cast and extruded composites and of the extruded monolithic 5083 aluminum alloy are discussed. Tensile tests were carried out at 25, 350 and 550 °C. The effects of extrusion on the properties of the composites were investigated. Three types of composites reinforced by as-received SiC particles, artificially oxidized SiC particles or Al 2O 3 particles and deformed at different temperatures are examined. Extrusion increases both the UTS and the elongation to fracture; whereas artificial oxidation of SiC particles (with 3.04 wt.% SiO 2) has the opposite effect. These properties are interpreted in terms of the various possible strengthening and fracture mechanisms as a function of temperature.

An AEM characterization of interfacial reactions in Al-MMC's reinforced with as-received and oxidized SiC particles

Interfacial reactions in MMC's can affect the mechanical properties of the material by changing the composition of the matrix and by forming new compounds at the matrix/ceramic interfaces. These reactions depend on the surface chemistry of the reinforcement, such as the presence of SiO2 produced by air oxidation of raw SiC particles. These reactions also depend on the processing route, particularly the thermal history of the material (fabrication or subsequent heat treatment or remelting). This paper presents results of an analytical transmission electron microscopy investigation of interfaces observed in Al-1% Mg alloys reinforced with 10 vol. % SiC particles. The composites were produced by the compocasting technique (semi-solid route) using as-received and oxidized SiC particles. The particles were oxidized in air at 1100°C for various times to produce oxidation levels ranging from 0-16 wt % measured by wet analysis.

Microscopic examination of the interface region in 6061-Al/SiC composites reinforced with as-received and oxidized SiC particles

Aluminum (6061) matrix composites reinforced with different SiC particles were processed. Black SiC particles were used in their as-received form or after artificial oxidation, leading to a 50-nm-thick SiO2 layer surrounding the SiC particles. The manufacturing route used was the compocasting technique, which allows maintenance of the semisolid slurry at relatively low temperatures (<650 °C) during the incorporation of the reinforcement. Before squeeze casting, the liquid alloy is held at 700 °C for 5 to 10 minutes. The interface between the aluminum matrix and SiC was characterized by transmission electron microscopy (TEM). Results show that no reaction takes place during compocasting between the as-received SiC particles and the molten aluminum. This is a consequence of the low temperatures and short holding times in the liquid state of the 6061 alloy, possible with this process. Prolonged holding at 800 °C of this material leads to extensive formation of A14C3. In the case of artificially oxidized SiC particles, the SiO2 layer surrounding the SiC particles reacts with the molten Al-Mg-Si alloy to produce MgAl2O4. However, the amount of Mg from the base alloy lost to form this spinel phase is not sufficient to prevent age hardening of the material.