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

Resumo

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.