Patents

The invention is based on a liquid metallurgy technique also named as stir-casting technique developed for synthesis of lightweight cenosphere reinforced metal syntactic foam. The cenospheres have densities between 0.2 to 1.0gm/cc having size range from 50 to 500 microns. Syntactic foam containing upto 60% volume fraction of cenospheres is developed. The steps involved in the process include: (i) melting of alloy, (ii) degassing and cleaning of the molten alloy, (iii) preheating of cenosphere, (iv) addition of preheated cenosphere through mechanical stirring using specially designed stirrer systems at a speed of 600rpm or more and (v) casting of the mixture in a permanent mould under low pressure. The process developed results in syntactic foam with uniform distribution of the cenospheres. The pore size and density of the material is controlled by the size, and the volume percent of cenosphere respectively. The aluminum-cenosphere syntactic foam thus developed has higher specific strength, stiffness and energy absorption as compared to dense aluminum alloy and composite or conventional aluminium foam.