Microstructural refinement of hyper-eutectic Al-Si-Fe-Mn cast alloys to produce a recyclable wrought material

Abstract

Although the cascade of material flow is presently suitable for the aluminum recycling, a better utilization of secondary alloys is required. In order to establish an upgradeable recycling design for developing wrought products from secondary aluminum alloys, a fine distribution of the primary phases in hyper-eutectic Al-Si-Fe-Mn cast materials has been achieved. Two novel processes were adopted. One was repeated thermomechanical treatment (RTMT), which involves a repetition of a multi-step cold-working followed by heat treatment. The other was rapid solidification by high-speed twin-roll casting to develop a fine solidification structure in a thin sheet. By applying these processes, refined microstructures were successfully obtained. Microstructural refinement by RTMT resulted in the avoidance of early fracture that was detected in the cast material by a tensile test. The RTMT imparted good ductility; therefore, it was possible to allow greater flexibility in the cold working of Al-Si-Fe-Mn cast materials. © 2005 The Japan Institute of Metals.