Fabrication and Performance of Aluminium Based Metal Matrix Composites with SiO2 and TiO2 as Reinforced Particles

Aluminum alloys are used in automobile and aerospace industries because of their low density and good mechanical properties, better wear resistance as compared to conventional metals and their alloys. In these industries there is continues demand to develop light weight, inexpensive and strong material which has led to the development of aluminum alloy metal matrix composites with ceramics as reinforcement particles. In this present work, aluminum based metal matrix composites have been fabricated using SiO2 and TiO2 as reinforcement materials by stir casting process and wear behaviour, hardness and breaking load have been evaluated.


Introduction
In manufacturing industry there is continues demand to develop light weight, inexpensive and strong material. This demand has led to the development of aluminum alloy metal matrix composites [1]. In these composites hard ceramic particles are reinforced. These materials are having very good mechanical properties. It is very easy to fabricate the composite and these can be moulded to any shape and size easily than conventional materials [2]. Therefore these materials are considered as potential engineering material for various engineering applications such as automotive and aerospace applications [3]. In recent past many researchers have developed different metal matrix composites.
Idrisi and Deva [4] studied the development and testing of Metal matrix composite by reinforcement of SiC particles on Al alloy and investigated the mechanical properties.It was concluded that mechanical properties were increased by increasing the percentage of SiC. Density was also increased by ultrasonic probe assistance at particular reinforcement particle level. Das et al. [5] studied the properties of ceramic reinforcement aluminium matrix composites. There was increase in the density, hardness and toughness with increasing the reinforcement fraction. The compressive strength of ceramic was increased to increase in reinforcement fraction. Mazahery and Shabani [6] studied the Micro structural and abrasive wear properties of SiC reinforced Aluminium-based composite produced by compo casting. The test of Tribological done by using a pin-on-disc wear tester, under dry sliding condition and different loads. It was found that there was increase in wear resistance and hardness of the composite material. Milos et al. [7] studied the aluminium-based composite materials in construction of transport means and concluded that mechanical properties of the composites depends upon the size and weight percentage of graphite and Al 2 O 3 . Idrisi et al. [8] studied the development and testing of Al 5083 alloy reinforced by Sic particles. The result showed that with increase in weight percentage of SiC, there was increase in tensile strength and compressive strength. Senapati et al. [9] studied the extensive literature review on the usage of fly as a reinforcement agent for different matrix. Fly ash was used in molten metal and cast because it can reduce the overall weight and density due to low density of fly ash.
It is clear from literature review that these materials give good mechanical and wear properties than conventional materials. There is a future scope to fabricate new composite which improve these properties. Therefore in this work aluminum based composites are fabricated with stir casting process by using Silicon dioxide, titanium dioxide and combination of these, as reinforced particles and mechanical properties have been investigated.

Experimentation
In this research work, Aluminium alloy was melted in a crucible by heating in a muffle furnance at 800℃ for 3 to 4 Universal Journal of Mechanical Engineering 3(4): 142-146, 2015 143 hours. The Silicon oxide particles and titanium oxide particles were preheated at 1000℃ and 900℃ respectively for 1 to 3 hours to make their surface oxidized. The furnance temperature was first raised above the liquidus temperature of aluminium near about 750℃. To melt the aluminum alloy completely and was then cooled down just below the liquidus to keep the slurry in semi solid state. Automatic stirring was carried out with the help of radial drilling machine for about 10 minutes at stirring rate of 290 RPM. At this stage, the preheated silicon oxide particles and titanium oxide particles were added manually to the vortex. In the final mixing processes the furnance temperature was controlled within 700±10℃. After stirring process the mixture was pour in the other mould to get desired shape of specimen. The presence of reinforcement throughout the specimen was inspected by cutting the casting at different locations and under microscopic examination. Same process was used for specimens with different compositions of silicon oxide and titanium oxide. Composition of samples is shown in table 1.   Figure 1 shows the comparison of hardness of different composites with different proportions of reinforcement particles.

Comparison of Hardness
The figure 1 shows that incorporation of silicon oxide and titanium oxide particles in Aluminium matrix causes reasonable increase in hardness. .Thus, silicon oxide and titanium oxide in Al casting reduces cost, decreases density and increase hardness which are needed in various industries like automotive etc [10].

Weight Loss of Al + SiO 2 and Al + SiO 2 +TiO 2 during
Wear Testing Weight losses of the different composites are shown in tables 2 and 3.
It is clear from the table 2 and 3 that with increase in the proportion of SiO 2 and SiO 2 +TiO 2 , wear resistance of the composite increases. Comparative analysis indicates that wear resistance of composite with SiO 2 +TiO 2 reinforcement particles is greater than that of composite with SiO 2 particles as reinforcement.  The figure 2 shows that incorporation of silicon oxide and titanium oxide particles in Aluminium matrix causes reasonable increase in breaking load thus increase the tensile strength. Thus, silicon oxide and titanium oxide in Al casting reduces cost, decreases density and tensile strength which are needed in various industries like automotive etc [10].

Results of SEM
Silicon Oxide is Mixed with Aluminium 6061

Conclusions
In this research work, different composite materials with different proportions of silicon oxide/titanium oxide reinforcement particles have been successfully fabricated and the following conclusions have been made: 1. The results confirmed that stir formed aluminium 6061 with silicon oxide/titanium oxide reinforced composites is clearly superior to based aluminium 6061 in compression of tensile strength, wear as well as hardness. 2. Addition of SiO 2 /TiO 2 in aluminium matrix improves the hardness of the matrix material. 3. The hardness increases after the addition of silicon oxide and titanium oxide particles in the matrix. 4. Wear resistance increases by adding SiO 2 /TiO 2 particles.