Effect of Fly Ash Addition on the Physical and Mechanical Properties of AA6063 Alloy Reinforcement

Alaa Mohammed Razzaq, Dayang Majid, Mohamad Ishak, Uday Basheer
2017 Metals  
Aluminum-fly ash particulate-reinforced composites (AA6063-FA) have been used in various engineering fields, such as automotive and aerospace industries, due to their low density and good mechanical properties. There are many fabrication techniques available to manufacture these composites according to matrix and reinforcement materials. The compocasting technique for the fabrication of the AA6063 matrix composite reinforced with fly ash particles is the focus of this research. Fly ash content
more » ... h. Fly ash content was in the range of 0-12 wt % in increasing increments of 2%. Fly ash particles were added to the molten AA6063 alloy until they were completely blended and cooled down just below the liquidus to keep the slurry in the semi-solid state. After this, the molten AA6063-FA composites were cast into prepared cast iron molds. Bulk density and apparent porosity measurements, Charpy impact testing, Vickers microhardness measurements, Field Emission Scanning Electron Microscope (FESEM), Variable Pressure Scanning Electron Microscope and Energy Dispersive X-ray spectroscope (EDS) elemental mapping were used to evaluate these materials. The results showed that an increase in the fly ash content in the melted leads results in an increase in the microhardness and porosity in the composites. In contrast, the bulk density and Charpy impact energy of the composites decreased with an increase in the fly ash content. Metals 2017, 7, 477 2 of 15 AA6063 alloy is widely employed for construction and transportation applications [5] . As a baseline material, it possesses good formability, weldability, machinability and corrosion resistance as well as a medium strength relative to other grades of aluminum alloys [6, 7] . However, with a view of implementing them as high performance materials for use in the aerospace, automobile, chemical and transportation industries, it is essential to improve the strength, elastic modulus and wear resistance of the AA6063 alloy compared to the conventional base [8] . Metal matrix composites (MMCs) is a macroscopic combination of two or more different materials (one of them is a metal and the other a non-metal) in which tailored properties are determined [9] . In recent years, the metal matrix composites have received considerable attention due to their low density, high strength and stiffness as compared to those of conventional materials [10] . The adhesive strength between the matrix and reinforcement plays an important role in the determination of mechanical properties for MMCs [11, 12] . Many researchers have discussed these aspects. Reinforcement particles incorporated into molten aluminum were observed to possibly guarantee the production of components with decent functional capacities in mechanical, structural and tribological applications [13] [14] [15] . Reinforcement is usually composed of non-metal components and generally conventional ceramic materials, such as SiC, Al 2 O 3 , fly ash and so on. Many important automotive components, such as pistons, cylinders, engine blocks, brakes, drive shafts and snow tire studs, have used aluminum matrix composites in their production. The new aluminum matrix composite engine has provided a higher compactness with great weight reductions compared with traditional engine blocks and those fabricated in aluminum alloys with other metal alloy liners, which thus provides a higher level of performance [16] . There are several fabrication techniques available to manufacture the MMC materials, such as casting, powder metallurgy and diffusion bonding. There is no unique way in this regard. Due to the choice of matrix and reinforcement as well as the relevant type of these materials, the fabrication techniques can vary considerably. The casting technique has received great attention in the last few decades for the fabrication of aluminum alloy components for different applications. The stir casting technique has proven to be the most promising technique amongst other liquid state production techniques. Sozhamannan et al. [17] investigated the influence of stir casting process parameters on the metal matrix composites. They showed that the reinforcement particles (SiC) are uniformly distributed in the aluminum matrix at the processing temperatures of 750 and 800 • C. The microhardness values increase with an increase in the temperature from 750 to 800 • C after 20 min of holding time. In addition, the impact energy values of aluminum matrix composites mainly depend on the distribution of the SiC particles in the matrix. The impact strength values are slightly increased with an increase in temperatures (700-900 • C). Khosravi et al. [18] studied the influence of the compocasting process parameters on the microstructure and mechanical properties of A356-SiC composites. Their results showed that uniformity in the SiC particle distribution was improved by increasing the stirring time and decreasing the stirring temperature. However, by increasing the stirring speed, the homogeneity first increases and then declines. In addition, they observed that the porosity of MMC increases by increasing the stirring speed, stirring time and temperature. Among various reinforced ceramic materials used, fly ash is one of the most cheaper and low-density reinforcement material available as a solid waste byproduct during combustion of coal in thermal power plants. The chemical composition of this ash consists of Al 2 O 3 , SiO 2 and Fe 2 O 3 as major constituents and MgO, CaO, K 2 O and Na 2 O as minor constituents [19] [20] [21] . The utilization of aluminum matrix composites with fly ash particles as reinforcement are likely to overcome the cost barrier for widespread applications, such as engineering, automotive and other applications. Many researchers have carried out various studies on the physical and mechanical properties of the aluminum matrix composites using fly ash as reinforcements [22] [23] [24] [25] [26] [27] [28] . For example, Selvam et al. [22] have studied the microstructure and mechanical properties of the AA6061 aluminum alloy reinforced with fly ash. The aluminum composites in this research were characterized as having homogeneous dispersion of fly ash particles with good bonds and a clear interface with the AA6061 aluminum
doi:10.3390/met7110477 fatcat:6zp4gbrmqrfpbkkz72gevxpwsa