SYNTHESIS AND CHARACTERIZATION OF CERAMIC WOOL AND GRAPHITE PARTICLES REINFORCED THIN SECTIONED - COMPOSITES

Abstract

Generally, aluminium and its alloys are of low modulus and medium strength. It is possible to add a small amount of reinforcement in the aluminium or its alloys to improve their modulus and strength. Easier fabrication and availability of ingredients make it very attractive. Since the particles are the cheapest reinforcements and results in isotropic properties in a composite while fibers provide greater strength threfore present study'focusses on graphite particles and ceramic wool composites. In the present work, Metal Matrix Composite (MMC) has been prepared in the form of hemispherical shell by reinforcing ceramic wool and graphite particles into commertially pure aluminium, using gravity stir cast method. Die steel mould is preheated in the range of 660°C to 700°C before pouring the melt at 800°C ±50°C into it. Graphite coating is used for easy stripping of casting. For graphite composite, graphite is preheated up to 900°C before mixing into the melt. Ceramic wool composite is prepared by keeping it into the die in the form of thin layer, preheating and liquid metal pouring is done subsequently. Castings are subsequently prepared for thickness mesurement, metallographic examination, hardness testing, tensile and compression tests. It has been observed that there is a gradual decrease in the thickness from periphery to centre e.g. 3.00, 2.8, 2.1, 1.6 and 1.4 mm. Volume fraction is also varying from periphery to centre. On an average, volume fraction of reinforced ceramic wool obtained -is 9.25 and 6.62% while for graphite composite is 7%. Tensile strength achieved for ceramic wool reinforced composite is found to be 61 MPa and for graphite it is 53 MPa. Compression strength for ceramic wool and graphite composites are 27.7 MPa and 22.8 MPa respectively. Macro-hardness values have been found to vary from site to site. This is due to the uneven distribution of reinforced material. It is clear from the results that hardness of ceramic wool reinforced composite is higher than graphite reinforced composite