Effect of Fe-Rich Intermetallics on Tensile Behavior of Al–Cu 206 Cast Alloys at Solid and Near-Solid States

Abstract

Iron is one of the most common impurity elements in Al–Cu 206 cast alloys as it often causes the precipitation of Fe-rich intermetallic phases during solidification due to its extremely low solid solubility in aluminum . The characteristics of the Fe-rich intermetallics , such as type, morphology, size, and distribution, have significant influences on the tensile behaviors of the Al alloys . In the present work, two Al–Cu 206 cast alloys containing different types of Fe-rich intermetallics (dominated by either platelet β-Fe or Chinese script α-Fe) were cast and their tensile tests were performed at both solid (room temperature) and near-solid (2.8 vol. % liquid) states. It is found that the tensile properties in both solid and near-solid states are improved when the Fe-rich intermetallics change from platelet to Chinese script morphologies. During the solid-state tensile deformation, the failure occurs mainly along the platelet β-Fe intermetallics/Al matrix interface or within the Chinese script α-Fe particles. In the near-solid state, the alloy containing mainly Chinese script α-Fe is found to have more free flow paths for liquid feeding, leading to improved tensile properties . By contrast, the platelet β-Fe can cause the blockage of the liquid flow paths, leading to the degraded tensile properties and worsened susceptibility to hot-tearing .