Effect of dendrite arm spacing on cleavage fracture toughness of Al–5Si–1Cu alloy

Abstract

The influence of dendrite arm spacing on mechanical properties, especially on the cleavage fracture toughness of Al–5Si–1Cu alloy, was investigated. Increasing the solidification rate results in a reduction of the secondary dendrite arm spacing λ2. Four different microstructures have been studied. The interdendritic area boundaries are a strong barrier for dislocation slip in the stressed alloy; they cause a change in the density and direction of the slip bands. The values of yield stress R0,2, tensile strength Rm and plane strain fracture toughness KIc for different varieties of Al–5Si–1Cu alloy microstructure have been determined. Relationships between mechanical properties and dendrite arm spacing were described in terms of the Hall Petch equation; a decrease in secondary dendrite arm spacing causes an increase in strength and to a lesser degree, in fracture toughness of Al–5Si–1Cu alloy.