Design and fabrication of functionally graded in-situ aluminium composites for automotive pistons

Engineering components with location specific properties are being designed and fabricated successfully using functionally graded materials (FGM). The present investigation aims at design, fabrication and evaluation of functionally graded automotive piston using in-situ primary silicon reinforced A390 aluminium composite by centrifugal casting technique with a view of obtaining improved thermo mechanical properties at specific locations. The dies are designed and fabricated so as to obtain the primary silicon rich region towards the head portion of the piston. FGM pistons with A390 and A390-0.5%Mg are produced. They are characterised along the vertical cross section of the piston from piston head towards the skirt by microstructural, chemical, mechanical, thermal and tribological characterisations methods. The results are also compared with that of gravity cast piston. Microstructure and chemical composition analysis of FGM piston shows graded distribution of primary silicon from the head portion of the piston towards skirt and a eutectic composition in the skirt region. That yields an increase in hardness towards the head region. The wear testing revealed that the gradation also resulted in a remarkable enhancement of the wear properties of the piston head. Keywords: Aluminium, Functionally graded material (FGM), Piston, Centrifugal casting