Effects of anisotropic microstructure of continuous cast Al-Cu eutectic alloys on their fatigue and tensile properties

The objective of this work is to explore the effects of anisotropic microstructure on the material properties of a continuous cast Al-33%Cu eutectic alloy, produced by the Ohno continuous casting technique (OCC). A clear anisotropic microstructure was obtained in the OCC samples, namely a fine lamellar eutectic structure with unidirectional growth along the axial direction. The eutectic structure was formed by a primary α-Al phase and secondary CuAl ₂ phase. The hardness of CuAl ₂ is about 2.8 times higher than that of the α-Al phase. Due to the anisotropic microstructure, the mechanical properties of the OCC samples depended on the loading direction. The tensile and fatigue properties of the OCC samples in the longitudinal direction were more than 30% higher than those in the perpendicular direction. In addition, the mechanical properties were influenced directly by the fine eutectic structure in the longitudinal direction. The ultimate tensile strength of the OCC sample in the longitudinal direction could be estimated theoretically using three different parameters: solid-solution strengthening, interlamellar eutectic structure and work hardening strengthening.