Deformation behaviors of pure Al and Al-4.5mass%Cu alloy in semi-solid state

Abstract

To clarify the mechanism of hot tearing in the ingot produced by direct chill (DC) casting, the mechanical properties and the deformation behaviors of pure Al and Al-4.5 mass% Cu alloys in the semi-solid state were investigated by a new tensile test method. The tensile strength and elongation on the Al-4.5 mass% Cu alloy decreased remarkably at the temperature above the solidus. And in situ observation, the healing by the liquid flow into the crack was observed at a high temperature range in the semi-solid state. Pure Al exhibited very high ductility until near the liquidus temperature. The deformation behaviors in the semisolid state of both alloys were classified into four stages based on their mechanical properties, fracture surface morphologies, and in situ observations on the tensile tests. The brittle temperature ranges in which hot tearing occurred in both alloys were determined. These data obtained from the tensile test in the semisolid state could be applied to several simulations.