PROPERTIES OF ALUMINIUM/ELECTROLESS Ni-COATED SiC COMPOSITES - A REVIEW

Abstract

The combination of properties of Al/SiC composites make them very attractive materials for applications in automotive and aerospace industries. Several techniques are used in developing Al/SiC composites but stir casting process is most commonly used because it is the simplest and cost effective technique. However, composites produced via stir casting suffer from limitations such as low wettability and inadequate bonding between the molten Al & SiC particulates and the formation of degrading interfacial products like aluminum carbide (Al4C3) which degrades the mechanical properties of the composite. Some of the techniques to improve Al-SiC wettability include addition of surface active elements such as magnesium, heat treatment of particles and application of metallic coating on the reinforcements before addition to the melt. Wetting agents alter the composition of the matrix alloy, while heat treatment of the reinforcement does not completely prevent the formation of Al4C3 when utilized. To reduce the direct interaction and promote wetting between reinforcements and molten aluminum during processing, the surface of SiC particulates can be modified by coating via oxidation, sol-gel and electroless processes. Of all these methods, electroless nickel deposition produces the best coatings with uniform thickness and adequate strength. In the present study, influence of electroless nickel-coating of SiC on the mechanical, corrosion and microstructural properties of Al/SiC composite has been evaluated. Finally, it can be concluded that the Ni and Ni3P intermetallic phases produced via electroless coating improves the wettability between the SiC and molten aluminium leading to enhanced properties of the composite.

Effect of SiO2 Surface Oxidation Coating of Silicon Carbide Particles Reinforcement on the Mechanical Properties of Al-2.5%Mg/xSiCp Developed by Stir Casting Method

“…Basically, oxidation can be defined as a reaction of metal and oxygen [2] but not limited to metal. In this study, the measured SiCp was heated in an Electrical Resistance Heating Furnace (Model: XD -1700M, manufactured by Zhengzhou Brother Furnace Co. LTD) already set to a temperature of 1300 o C required for the surface oxidation to take place, where a thin layer of SiO2 was formed on its surface.…”

“…The fabrication of composite materials is meant to produce materials with enhanced performances compared to its matrix alloy. It is observed that aluminium alloys are primary material of consideration for structural application but owning to their low strength behaviors, they are unsuccessful in service to meet the ever-increasing demands for high structural application performances [1][2][3][4]. Hence, ceramic particles like SiCp are used as reinforcement to strengthening the aluminium alloys to meet high structural applications [5].…”

“…Nevertheless, it was observed that there is a poor wettability of SiCp with molten aluminium [7]. The poor wettability of SiCp in molten Al alloys poses a limitation in the development of Al-SiCp composites [8], which could be ascribed to a poor interfacial reaction, an insufficient interfacial contact, and weak bonding between the Al alloy matrix and the SiCp reinforcement [2,9]. These poor wetting creates uneven dispersion of SiCp particles in the molten Al alloy matrix, thereby reduces mechanical performances and creates high porosity in the composites developed [10].…”

“…Surface oxidation activates the surface as it replaces surface covalent bonds with surface ionic bonds possessing enhanced adhesion between the reinforcement particles and the matrix phases, thereby influence the composites mechanical properties [12]. Surface oxidation prevents the formation of an harmful Al4C3 from the chemical reaction during the production of composites by developing a silicon oxide layer between the SiCp particles and the Al-Mg metallic matrix [2,12], thereby influences the mechanical behaviors and performance of the composites developed. Also, Urena, 2014 reported that heat treatment of reinforcement particles prior to its dispersion into the molten aluminium assist their transfer by creating oxide formation.…”

Study on the Optimization of Surface Modification Processing of SiCp and Tribological Properties of AA6061-SiCp based Composites

“…Figure 1: Industrial usage of reinforcement materials (Odiwo et al, 2021) Many techniques are available for the fabrication of aluminium/silicon carbide particulate composites such as spray deposition, powder metallurgy, infiltration technique, squeeze casting and stir casting. However, stir casting is one of the most commonly used method to fabricate aluminium matrix composites because of its simplicity, ease of production of complex casting, mass production possibility and it is economical (Ramesh et al, 2010).…”