Change of Microstructure and Hardness of Duo-Casted Al3003/Al4004 Clad Material during Extrusion Process

Abstract

This study was carried out to observe and measure the microstructure, distance between dendrite arms, aspect ratio, and Knoop hardness change of extruded material formed by the hydro co-extrusion of Al3003/Al4004 clad material manufactured by the duo-casting method. The specimen of duo-casted Al3003/Al4004 clad materials was circle shaped; it was composed of Al3003 (outside) and Al4004 (inside) materials. The manufacturing conditions of the hydro co-extruded specimen were 423 K temperature and 6.5 ratio of extrusion. At the interface of the duo-casted Al3003/Al4004 clad material, a non-junction at the interface and non-metallic inclusions of Si- and Mn-based oxides were observed. Al3003 exhibits equiaxed crystals; Al4004 has a casted structure with dendrites before extrusion, showed slight deformation during extrusion, and then finally exhibited completely deformed structures after extrusion. In the cast material, the distance between dendrite arms increased, and the aspect ratio of dendrites tended to decrease from the surface to the center. However, in the case of the extruded material, neither Al3003 nor Al4004 changed significantly from the surface to the inside. As extrusion progressed, the Knoop hardness value at the interface of Al3003/Al4004 increased rapidly compared with those of Al3003 and Al4004 matrixes.