Development of Selectively Reinforced Squeeze Cast Pistons

This paper presents the development of selectively reinforced metal matrix composite (MMC) piston and the associated squeeze casting facility. The need for materials with property mixes and enhanced thermal stability has focused much interest on the development of MMCs, as they offer considerable promise to automotive engineers. The benefits are many fold. The important ones include reduced weight, low thermal expansion, leading to reduced problem of engine seizure and improved wear resistance. Among the various processing methods of MMCs, squeeze casting provides several advantages such as finer microstructure, freedom from porosity, more ductility etc. A squeeze casting machine has been designed and developed, where most of the operations are automatic, except preform placing, product pickup and die cleaning. A selectively reinforced piston has been developed using this facility. The material system consists of aluminium - silicon alloy and alumina-silicate short fibre preform. The piston has been reinforced in the top ring groove and land area only. They have been engine tested and performance is found to be quite satisfactory. The presence of ceramic insert in the top ring region results in improved groove wear resistance. Microstructural studies reveal excellent interfacial bonding and absence of any porosity. This product development is an outcome of the Institute - Industry collaborative project, involving Indian Institute of Technology, Madras and M/s. India Pistons Ltd., Chennai.