25-10-2016, 12:19 PM
Characterization of Silicon Carbide Reinforced Aluminum Matrix Composites by Using Stir Casting Method
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Abstract: The objective of this work is to study about the wear characteristics, microstructure and the mechanical properties of cast silicon carbide (SiC) reinforced aluminum matrix composites (AMCs). AMCs of varying SiC content (0, 3 and 7 wt.%) were prepared by stir casting process. Wear performance, microstructure, hardness, tensile strength and compressive strength of the prepared composites were analyzed. The results were analyzed and it showed that adding SiC reinforcements in aluminum (Al) matrix increased wear resistance, tensile strength and compressive strength and 7 wt. % SiC reinforced AMC showed maximum wear resistance, tensile strength and compressive strength. Microstructural observation revealed clustering and non-homogeneous distribution of SiC particles in the Al matrix. Pin-on-disc wear test indicated that reinforcing Al matrix with SiC particles increased wear resistance
INTRODUCTION
Metallic matrix composites are the components which are formed by combinations of two or more different metals, intermetallic compounds or second phases are rooted within the metallic matrix. They are formed by controlling the morphologies of the constituents to get best combination of properties. Properties of the composites depend on the properties of the constituent phases, their relative amount, and discrete phase geometry including particle size, shape and orientation in the matrix [1, 2].
AMCs have got wide applications in our day to-day life. There are several advantages in using particle reinforced AMCs materials than unreinforced materials such as- light weight, low thermal expansion coefficient, high thermal conductivity, greater strength, high specific modulus, improved stiffness, increased wear resistance and improved damping capabilities. Reinforcing constituents can be included in the matrix in the form of particles, small fibers, continuous fibers or mono filaments. Now this is used in industrial products, aerospace, thermal management areas, automotive applications such as engine piston, brake disc etc. [3]
AMCs can be prepared by liquid state processing (squeeze casting, stir casting, infiltration etc.), semi-solid processing and powder metallurgical route. Generally nonmetallic and ceramic particles like alumina (AL2O3), boron carbide (B4C), silicon carbide (SiC), graphite etc. are used as reinforcements in AMCs.
As the loads are applied externally to the composites, metal matrix transmits loads to the reinforcements and then loads are carried by discreted reinforcements that are bonded with the matrix. Strong interface link between reinforcements and matrix is necessary to attain high strength of the composites. Interface link is obtained by reaction or mutual dissolution during casting process. Hence, good wetting of the reinforcements is essential during casting process. [4]
The objective of this study is to examine the result of SiC reinforcements in Al matrix composites on mechanical properties such as tensile strength, compressive strength, micro-structural aspects and wear resistance.
2. EXPERIMENTAL
2.1 Materials
Al was used as matrix material and powdered
form of the SiC (3 and 7 wt. %) was added as the reinforcements in the stir casting process to prepare composites in this study.
Preparation of composites
SiC reinforced AMCs were prepared by stir casting process. Crucible made up of carbide material is used because of its high temperature resistance. First the pure solid Al was melted in furnace and when the temperature of the liquid Al reached around at 700-750oC, SiC powder is added in molten Al metal. An electrical resistance furnace which was assembled with the graphite impeller used as stirrer was used for stirring purpose.
Wear test
The wear of pure aluminum is more, so as to reduce this sic is reinforced in al matrix. The specimen with 3% and 7% SiC-Aluminium composition were tested. The loss of material of pure Aluminum was more as compared to the 3% SiC-Aluminum and 7% SiC- Aluminum. Now when comparing wear of 3% and 7% SiC-Aluminium specimens we found that the wear of 3% SiC-Aluminum composite was more than that of 7% SiC-Aluminum specimen. This indicates that when the amount of SiC reinforcement increases in the Al matrix loss of material due to wear is less. Hence, the wear resistance increases with increase in SiC. [11, 12]
CONCLUSION
In our present study, AMCs were prepared by stir casting process with varying SiC content of 3% and 7% in Al matrix. Microstructural aspects, hardness, tensile strength, compressive strength and wear characteristics of the prepared composites were studied. Based on experimental estimation, we had these following conclusions:
01. Wear characterstics of AMCs resulted that increase in SiC % content in Al matrix increases the wear resistant, as it can be concluded that 7 wt.% SiC content AMC showed minimum wear loss than 3 wt.% SiC content AMC and pure Al matrix.
02. The microstructural studies revealed the fairly distribution of SiC particles in Al matrix and also porosities were observed in the microstructures.
03. The result of study suggest that with increase in composition of SiC in Al matrix the Rockwell hardness of the AMCs also increases as we had the greater hardness for 7 wt.% SiC content AMC than 3 wt% SiC content AMC and pure Aluminium.
4. With increase in percentage of SiC reinforcements in Al alloy increases the tensile strength and compressive strength. Here in our study and analysis we got them maximum for 7wt. % SiC content AMCs as compared to 3wt. % SiC content AMCs and pure Aluminum metal.