Effect of lead on the structure and phase composition of an Al–5% Si–4% Cu casting alloy

Abstract

The phase transformations in the Al–Cu–Si–Pb system have been studied using calculations. It is shown that the aluminum-based solid solution is in equilibrium only with the Al2Cu, (Si), and (Pb) phases, which correspond to the relevant binary systems. Reported polythermal and isothermal sections show that the Al–Cu–Si–Pb system is characterized by a significant liquid miscibility gap. The effect of lead on the structure and phase composition of an Al–5% Si–4% Cu alloy in the as-cast and annealed states is studied. Lead inclusions are located at the boundaries of dendritic (Al) cells and are globular in the as-cast alloy and after annealing at 500°C. The presence of lead phase does not affect the precipitation hardening upon quenching and aging.