P.O. Babalola

Aluminum Silicon Carbide Particulate Metal Matrix Composite Development Via Stir Casting Processing

In this paper, conventional simple methods of producing MMC with attained properties through the dispersion of silicon carbide in the matrix are investigated. To achieve these objectives a two-step mixing method of stir casting technique was employed. Aluminum (99.66 %C.P) and SiC (320 and 1200 grits) were chosen as matrix and reinforcement materials respectively. Experiments were conducted by varying the weight fraction of SiC for 2.5 %, 5.0 %, 7.5 % and 10 %. The result indicated that the stir casting method was quite successful to obtain uniform dispersion of reinforcement in the matrix. This was evident by the improvement of properties of composites over the base metal. Reinforced Aluminum Silicon Carbide (ASC) showed an increase in Young’s modulus (E) and hardness above the unreinforced case and marginal reduction of electrical conductivity was recorded for the composites. The silicon carbide of 1200 grits (3 μm) showed increased Young’s modulus (E) and hardness of 1517.6 Mpa and 26.1 Hv values at 7.5% volume fraction silicon carbide; when compared with the silicon carbide 320 grit (29 μm). Also; the electrical conductivity properties of the two grit sizes of the silicon carbides were less than the base metal for all the volume fractions of silicon carbide.

Influence of the Grit size of Silicon Carbide Particles on the Mechanical and Electrical Properties of Stir Casting Aluminum Matrix Composite Material

This paper studies the influence of the grit size of silicon carbide particles on the mechanical and electrical properties of stir cast aluminum matrix composites. A two step-mixing method of stir casting technique at (500 rpm) has been adopted. Type 1170 Al with (99.66 % C.P) and silicon carbide (SiC) particulates of 240 grit size (45 µm), 320 grit size (29 µm), 600 grit size (9 µm) and 1200 grit size (3 µm) were used. The incorporation of weight fraction of SiC ranges from 2.5 %, 5 %, 7.5 % and 10 %. The microstructures of the produced composites were examined using a scanning electron microscope. Mechanical properties were determined by using a universal testing machine of 30 KN load. Microhardness was performed on the composite specimens by using a LECO 700 HT tester with a load of 492.3 N and with a dwell time of 10 seconds. The electrical properties were determined using a Keithley instrument Model 2400 point probe machine. The results show that the modulus, yield strength and hardness of the composite increase at lower grit sizes of silicon carbide of 3 micron. The maximum hardness of 26.1 HVN and maximum modulus elasticity of 1517.6 N/mm -2 was obtained at 7.5 % weight fraction of SiC. A boost in the mechanical and electrical properties of the produced alloys was gained by changing the grit size of the silicon carbide.

Corrosion polarization behavior and microstructural analysis of AA1070 aluminium silicon carbide matrix composites in acid chloride concentrations

Abstract The effect of SiC content and NaCl concentration on the corrosion resistance of AA1070 aluminium in 2 M H2SO4 was evaluated with potentiodynamic polarization technique, open circuit potential measurement (OCP) and optical microscopy. Results showed SiC increased the corrosion susceptibility of the alloy at lower NaCl concentrations compared to results obtained at 0% NaCl which showed significant decrease in corrosion rates, with maximum inhibition efficiency of 90.84% at 20% SiC content. The corrosion rates decreased at higher NaCl concentration, with maximum inhibition efficiency of 94.12 and 77.27% at 20% SiC. Alloy samples in 2 M H2SO4/0% NaCl at 0 and 20% SiC visibly decreased in OCP value over wide variation compared to samples with varying NaCl concentration due to loss of passivity. OCP values for alloys at varying NaCl concentration decreased over a very short variation due to repassivation. Statistical data showed silicon carbide to be the only relevant variable responsible for the corrosion rate values with F-values of 8.85 corresponding to a percentage significance of 54.8%. Optical images showed the presence of corrosion pits of smaller dimension, yet deeper on the morphology of the alloy without silicon carbide compared the alloy containing it, whose corrosion pits, seems wider but very shallow.