Production of Leaded Aluminum Alloys by Rheocasting

Abstract

A vacuum rheocasting technique in which a solidifying alloy is violently agitated at high speed has been applied to production of some new bearing aluminum base alloys containing 15 to 50 mass%Pb. Rheocast microstructures of Al-Pb alloys have been observed using scanning electron microscopy. Coarse lead-rich phases in them are uniformly scattered coexisting with fine eutectics between aluminum-rich primary solid particles formed by destruction of dendrites. The torque of a stirrer inserted in the vacuum-melted alloys has been continuously measured during the rotation of stirrer at a speed of 70 s⁻¹ from the beginning to the final stage of solidification. The apparent viscosity of the semi-solid alloys is evaluated on the basis of the values of torque. The ultimate tensile strength and elongation have been investigated at room temperature and at elevated temperatures. A comparison of the mechanical properties of Al-Pb alloys with those of existing bearing alloys shows that the leaded aluminum alloy is a high cost-performance material.