Fabrication of functionally graded pistons by new melt process (Cast-Decant-Cast)

the cast-decant-cast (CDC) is a new process for producing functionally gradient components that has been developed lately in Dublin University. The procedure involves the introduction of the firstliquid, alloy A, into a mould, allowing it to partially solidify against the mould walls, then decanting anyunsolidified material, leaving a shell of alloy A against the mould wall. Alloy B is then introduced into the mould in a superheated state, partially remelting the inner layer of alloy A, thus mixing with it andforming a smooth gradient between alloys A and B. This procedure can produce the functionally gradient piston with radial gradient, i.e. being of toughness and low machining costs alloy B (A356) in core of the part and high wear resistant alloy A (A390) in surface the part. In this paper especially the effect of superheat of alloy B at different temperature of 750, 820 and 860 C̊ have been investigated.Characterization of the interface was carried out by OM and SEM microscope and the width of interface area was measured by microhardness test. Results showed that the best interface and wide interface at 860 C̊ has been obtained. Also wear resistance test was occurred to measure and compare the surface wear resistant to core.

Keywords:

A390 Alloy , functionally graded material , cast-decant-cast process