Possibility of Elevation of Mechanical Properties of Sand-Cast Copper Silumins

Abstract

The effect of heat treatment modes of copper silumins with 4% Cu and different concentrations of silicon and magnesium crystallized in sand molds on their microstructure and mechanical properties is studied. It is shown that the level of the strength and ductility parameters of the copper silumins after the treatment depends primarily on the degree of dissolution of phase CuAl₂ and that the concentration of magnesium in copper silumins with 4% Si + 4% Cu should not exceed 0.1 – 0.12%, which is sufficient for raising the strength characteristics without noticeable degradation of the ductility. The optimum mode for aging of alloy Al – 4% Si – 3.9% Cu – 0.13% Mg (160°C, 8 h), which provides σ_0.2 = 330 MPa, σ_r = 400 MPa and δ = 2%, is determined by computation.