Papers by Keyword: Silicon Carbide Particles

Abstract: To evaluate the fatigue behaviors of AZ61 magnesium alloy with different weight percentages (0, 1 and 2) of silicon carbide particles (SiCp) were fabricated through gravity casting method. In addition, stress-controlled low-cycle fatigue test of SiCp reinforced magnesium alloys AZ61 were performed in ambient atmosphere at room temperature using ASTM 606 standard specimens. Fatigue measurement results proved, that the fatigue life of SiCp reinforced metal matrix composites (MMCs) decreased with increasing SiCp content. However, the results of the cyclic ductility decreased owing to the presence of significant amount of SiCp, which induces the brittleness of fatigue properties. This is probably occurring because of increasing the SiCp content in the matrix causes highly localized plastic strain. In addition, a high concentration of stress results around the reinforcements particles regions initiate the crack leading to rapid failure of MMCs. Therefore, the SiCp did not act as a stress reliever and it behaves in a brittle manner for the crack propagation through the particles.

Abstract: The wettability between silicon carbide and aluminum is poor, silicon carbide is difficult to fuse or the distribution of silicon carbide is not uniform in the ingot when the SiCp / 7075 composite is prepared by melt casting.The surface modification of SiCp by nickel plating can significantly reduce the wetting angle of SiC/Al and improve the distribution uniformity of silicon carbide in SiCp / 7075. In this thesis, the thermal compression process 6.5% SiCp / 7075 reinforced by nickel-plated modified silicon carbide is simulated by DEFOEM-3D software.The influence of the shape and particle size of nickel-plated modified silicon carbide on its compressive damage has been highlighted, and the deformation characteristics of the SiC/Ni/Al interface layer in the thermal compression process have been discussed. The numerical simulation results show that the 6.5% SiCp / 7075 reinforced by spherical nickel-plated modified silicon carbide particles with a particle size of 15 μm has the smallest compression damage value of 0.0426, at this point the compression temperature is 400°C, the compression ratio is 15, and the compression rate is 0.03s^-1. the hot compression test of 6.5% SiCp / 7075 reinforced by spherical nickel-plated modified silicon carbide particles with a particle size of 15 μm was performed by using the same compression parameters as the numerical simulation. After hot pressing, the sample had a smooth surface with few obvious cracks, which was consistent with the numerical simulation results. Key words: nickel-plating modification; silicon carbide particles; compressive damage; grain size; grain morphology

Abstract: The paper is a synthesis of essential data regarding the wetting conditions in aluminium – silicon carbide mixtures. Non wetting conditions between the reinforcing element and the matrix turns difficult the incorporation of particles in the aluminium melt. The wettability depends on several elements, like the presence of the oxide layer at the melt surface, temperature, pressure or shape of the complementary material. To improve wetting conditions, several measures are necessary: alloying of the melt with surface active elements, overheating of the melt; coating of the particles with a metallic thin layer. Also, by using existing data reported in the field, some parameters were calculated and interpreted.

Abstract: The introduction of the metal matrix composites as the advanced electronic packaging materials is highly anticipated because their thermal properties can be engineered to match those of semiconductors, ceramics substrates and optical fibers. Among these advanced packaging materials, silicon carbide particles reinforced copper matrix (Cu-SiC_p) composites are highly rated due to the high thermal conductivity of copper and low coefficient of thermal expansion (CTE) of silicon carbide. However, the Cu-SiC_p composites fabricated via the conventional powder metallurgy (PM) technique usually have immature thermophysical properties due to the weak bonding between the copper matrix and the SiC_p reinforcement. In order to improve the bonding between the two constituents, the SiC_p were coated with copper via electroless coating process prior to PM fabrication processes. Based on the experimental results, The CTE and porosity of the Cu-SiC_p composites were significantly affected by the volume fraction of SiC_p. Furthermore, the CTE and porosity of the Cu-Coated Cu-SiC_p composites were significantly lower than the non-Coated Cu-SiC_p composites. These differences were mainly contributed by the nature of the bonding between the copper matrix and SiC_p reinforcement.

Abstract: The demand for advanced thermal management materials such as silicon carbide reinforced copper matrix (Cu-SiC_p) composites is increasing due to their high thermal conductivity and low CTE properties. However, the weak bonding between the copper matrix and the SiC_p reinforcement degrades the thermophysical properties of the composites. In order to improve the bonding between the two constituents, the SiC_p were copper coated (Cu-Coated) via electroless coating process. Based on the experimental results, the CTE values of the Cu-Coated Cu-SiC_p composites were found significantly lower than those of the non-Coated Cu-SiC_p composites. The CTEs of the Cu-Coated Cu-SiC_p composites were in agreement with Kernels model which accounts for both the shear and isostatic stresses developed in the component phases.

Abstract: The widespread use of metal matrix composites as the packaging materials is due to their tailorable thermal conductivity and coefficient of thermal expansion (CTE). For the same reason, silicon carbide reinforced copper matrix (Cu-SiC_p) composites are highly rated as thermal management materials in the electronic packaging applications. However, the Cu-SiC_p composites fabricated via the conventional powder metallurgy methods have inferior thermophysical properties due to the presence of porosity in the interface of copper matrix and the SiC_p reinforcement. In order to improve the bonding between the two constituents, the SiC_p were coated with copper via electroless coating process. Based on the experimental results, the CTE values of the copper coated Cu-SiC_p composites were found significantly lower than those of the non-Coated Cu-SiC_p composites. The CTEs of the composites tend to decrease as the porosity increases. The significant difference in the CTE values was related to the presence of sub-micron gap between the copper matrix and the SiC_p reinforcement.

Abstract: The paper presents the principal aspects regarding the obtaining of the mixture aluminium - silicon carbide particles. It is discussed about the wetting conditions and the critical acceleration necessary for the incorporation of particles into the melt. The high values obtained for this parameter involve applying some methods to improve the wettability: the covering of the complementary material with a thin layer of Ni, the alloying of the aluminium melt, the overheating of the metallic bath and the heat treatment of the silicon carbide particles. Also, the mechanical stirring conditions necessary to realize the mixture are presented. The settling process of the silicon carbide particles in the melt as a function of particles size, shape and volumetric concentration is also analysed. The presence of complementary material leads to the growth of the mixture viscosity. Therefore, the liquid alloy was investigated like a continuous medium in connection with the apparent viscosity. The main aspects regarding the solidification of metallic composites processed by casting method based upon theoretical concepts, general knowledge about casting of composites and experimental data are discussed. Finally, the specific defects caused by an insufficiently controlled solidification process and prevention measures are shown.

Abstract: Magnesium metal matrix composites (MMCs) have been receiving attention in recent years as an attractive choice for aerospace and automotive applications because of their low density and superior specific properties. Using stir casting process, AZ91 magnesium alloy metal matrix composites have been produced with different weight percentages (5, 10, 15, 20 and 25) of silicon carbide particles (SiC_p) addition. Microstructural characterization reveals uniform distribution of SiC particles with good interfacial bonding between the matrix and reinforcement. Electrical conductivity and Co-efficient of Thermal Expansion (CTE) measurements carried out on these composites have yielded better properties. Improved mechanical properties such as hardness, ultimate tensile strength, and compressive strength are obtained. The microfracture mechanisms involved during tensile fracture is analyzed and correlated with the properties obtained.

Abstract: Interaction of Al-Si alloys with SiC/C ceramic particles and their influence on microstructure of composites was discussed. This article presents a significant effect of modifying additives introduced into liquid aluminium. As it was shown in the research, Mg and Sr modifiers improve wetting conditions in Al/SiCp+Cp systems, as well as influence the composite’s structure and the structure of the interface between the components. The microstructure observations were performed using light microscopy (OLYMPUS GX 71) and scanning electron microscopy (PHILIPS XL30). Moreover, local analyses of chemical compositions as well as chemical elements mapping were performed using an EDX module for microarea chemical analysis. Based on structural studies, it was found that chemical composition of the aluminium alloy and its modification are equally important parameters.