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Fabrication and Characterization of Aluminium-rice Husk Ash Composite Prepared by Stir Casting Method

Adnan Adib Ahamed*
Department of Materials and Metallurgical Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh.

Rashed Ahmed
Department of Materials and Metallurgical Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh.

Muhammad Benzir Hossain
Department of Materials and Metallurgical Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh.

Masum Billah
Department of Materials and Metallurgical Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh.

Abstract/ Executive Summary:

Metal Matrix Composites (MMCs) constitute an important category of design and weightefficient materials. This article highlights on the work where an attempt is taken to fabricate aluminium matrix composite reinforced with rice husk ash (RHA) particles, an agricultural byproduct with high amount of silica. RHA particles, upon analysis, are incorporated into the Al matrix melt by stir casting. Magnesium (~1%) is used as a wetting agent between matrix and reinforcement. 3, 6 and 9% wt. of RHA are added into the matrix. The microstructure analysis reveals the reinforcing particle distribution inside the matrix which indicates successful fabrication of the composites. The density and mechanical properties such as strength and hardness are measured for both unreinforced metal and composites. The results found in the tests show a decrease in density with increasing reinforcement while increasing yield strength, ultimate strength and hardness of the composites with increasing reinforcement from the unreinforced condition.

Keywords: Metal matrix composites; Aluminium; Rice husk ash; Stir casting; microstructre; Mechanical properties.

Location: Shibganj, Chapainawabganj, Bangladesh

Start Date:

End Date:

Program Area: Resource Development and Management

Commodity: Rice husk, Ash

Objectives:

In this work, Rice Husk Ash was used as the reinforcement. The main idea was to utilize the agro-industrial waste to reduce its negative environmental impact and at the same time to develop a composite material economically with superior properties.

Methodology:

Materials selection The matrix material used in this study was commercially pure aluminium of 99.3% purity and the reinforcement material was rice husk ash prepared from the rice husks collected from Shibganj, Chapainawabganj, Bangladesh. Magnesium at about 1% of the weight of the matrix was used as the wetting agent for the better adhesion of the reinforcements with the matrix. Mg addition reduces the casting fluidity at the same time it reduces the surface tension of the aluminium. The Mg addition was limited to 1% as increasing the content above 1% of the matrix weight increases the viscosity of the slurry to the detriment of particle distribution. B. Rice husk ash preparation The rice husks were washed thoroughly with water to remove the dusts and dried at room temperature for 24 hours. They were then burnt at open atmosphere to remove the moisture and organic constituents. The color of the husk changed from yellowish to black at this stage due to charring of the organic matter. This was followed by heating the husks at 650^oC in a heat treatment furnace (Model: SPX Blue M Hi-Treet) for two hours to remove the carbonaceous constituents leaving the grayish which silica rich ash to be used as the reinforcement of the composite. The ash was subjected to chemical analysis by adding drops of HF acid and heating 0.1gm of RHA so that the silica content is evaporated as SiF4 and weighing of the residue afterwards determined the percentage of silica content in the ash. C. Composite making The composite was made by stir casting method. Initially 1.2kg of Al was charged into a graphite crucible and melted to 810^oC in a pit furnace. As the metal melted, about 15gm of magnesium was added to the melt as a wetting agent between matrix and reinforcement since it reduces the casting fluidity as well as the surface tension of the molten Al. The Fabrication and Characterization of Aluminium-Rice Husk Ash Composite Prepared by Stir Casting Method molten Al was then transferred to the holding furnace of the stir casting apparatus. RHA particles were preheated to 700^oC for 1hour so that the silica content remained amorphous below 800^oC. The graphite stirrer was lowered into the melt and stirring was commenced at 500 rpm to create a vortex. The preheated RHA (~105-420µm) was added slowly into the melt at the side of the vortex to ensure a uniform distribution. The stirring was continued for another 7-8 minutes after adding the reinforcement so that the particle distribution and the mixing is done properly. The mixture was poured at a temperature of 732^oC into a mild steel permanent mold that was preheated earlier to obtain uniform solidification of the casting. In this process 3, 6 and 9% RHA reinforced Al matrix composites were prepared.

Source of Information: Rajshahi University Journal of Science & Engineering ISSN 2309-0952 Vol. 44: 9-18, 2016

Article Link (Online Journal):

Funding Source:

1.

Budget:

Total Budget (Tk.) :

Achievement/Findings:

From the work it can be concluded that RHA can be successfully incorporated into pure aluminium matrix for the production of composites. This can also solve the problem of storage and disposal of RHA and utilization of an agricultural waste. Addition of up to 9% by weight RHA to aluminium was done by stir casting route to produce composites. Addition of magnesium improved the wettability of RHA with aluminium melt and thus increased the retention of the RHA in the composite. Hardness of the composites is increased from 22BHN to 33 BHN with addition of RHA and magnesium compared to unreinforced condition. The Ultimate tensile strength and the yield strength has improved with increase in RHA content while decreasing the density ensuring the potential application of materials with lighter weight but superior strength.

Knowledge Management: Journal