Study on the Material Engineering aspects of Microwave sintered Aluminum– Cenospheres Composites

Abstract

The thesis brings out the findings from the study undertaken on development of Aluminium based Metal Matrix composite through Powder Metallurgy route. The composite has been fabricated reinforced with various volume percentages of Fly ash Cenospheres particulates ranging from 0 to 50 vol %. The densification of the composites has been achieved through a non conventional sintering route known as Microwave sintering which is different from the well known conventional processing routes. The microwave sintering process appears rapid and economical. The Aluminium composites reinforced with Cenospheres and sintering through Microwave sintered composites have been later characterized for physical properties such as Density, Porosity, Hardness and Water Absorption, Chemical characteristics and Morphology of the synthesized composites and that of the raw materials through Scanning Electron Microscopy and Energy Dispersive X-ray Fluorescence methods. The Phase Analysis of the composites has been carried through Powder route X-ray Diffraction. The composites have also been studied for Mechanical properties such as Compression Strength with Finite Element Analysis and Modulus of Rupture. The composites have been studied for Tribological properties such as Wear and Erosion Resistance, Thermal properties such as Co-efficient of Thermal Expansion, Thermal Shock Resistance and Fusion Temperatures. The above test results have been compared with the results of conventionally prepared AMCs. The study on the various properties on the PM based Aluminium Cenospheres composites sintered in Microwave at 6650C have indicated that Apparent Porosity was about 35% compared to conventionally sintered ones which was around 40.7%. The Bulk Density was seen to reduce from 2.2 to 1.75 g/cc and the BHN values were found decreasing from 46 to 24% for the Microwave sintered samples. The conventionally sintered sample showed Bulk Density reducing from of 2.1to 1.75 g/cc and BHN values were found decreasing from 46 to 24. The BHN values were better than the conventional ones by about 26 %. The CTE of the composites decreased from 25.6 to 7.4 x 10-6/0C with increase in cenospheres content from 0 to 50 vol % forx the conventionally sintered composites. For the microwave sintered composites, the CTE of the composites decreased as the cenospheres content from 25.6 to 3.6 x 10- 6/0C which is much lower than the conventionally sintered samples by 51%. The microwave sintered composites showed lesser erosion loss by about 12-15% compared to conventionally sintered samples. The slide wear data shows that conventionally sintered samples has higher slide wear losses compared to conventionally sintered ones by about 86%. The Flexural strength of the conventionally sintered composites was seen decreasing from 52 to 8.8 MPa while Flexural strength of microwave sintered composites were decreasing from 71.9 to 31.5 MPa with increase in cenospheres content from 10 to 50 vol %. MW sintered was better by about 40% in Flexural Strength compared to the conventionally sintered composites. The Compression strength of the composites containing Cenospheres from 10 vol. % to 50 vol. % was found to decrease from 140.3 to 71.7 MPa with the increase in Cenospheres content, for microwave sintered samples. For the conventionally sintered composites the strength reduced from 140.3 to 71.7 MPa. The compressive strength of microwave sintered samples was more by 17.4 % compared to the conventionally sintered samples. Aluminium metal matrix composites can be fabricated through powder metallurgy route sintered in microwave sintering which is found to be adoptive & effective rapid sintering method. It is possible to fabricate Aluminium Cenospheres ‘Syntactic Foams’ through powder metallurgy microwave sintering and the properties for the same match with those materials for applications in automotives.