EFFECT OF CHEMICAL-COMPOSITION ON APPARENT VISCOSITY OF SEMISOLID ALLOYS

Stirring experiments of Al, Cu and Fe-based semi-solid alloys on conti nuous cooling were carried out to investigate the effect of chemical c omposition on the apparent viscosity of semi-solid alloy slurries. The apparent viscosity for these alloys increased with increasing solidif ication rate and decreasing shear rate, and the critical fraction of s olid for fluidity increased with decreasing solidification rate and in creasing shear rate. The equation for apparent viscosity eta(a) of sem i-solid alloy was proposed as follows: [GRAPHICS] where eta(La) is the apparent viscosity of liquid, rho(m) is the density of alloy, C is th e solidification rate, gamma is the shear rate and f(s) is the fractio n of solid. The alpha and beta values depended on chemical composition of alloys and became larger with increasing solute content X. These r esults were explained by the shape parameter value of suspended partic les and the volume fraction of liquid trapped between suspended partic les in semi-solid alloys.