Measurements of microhardness during transient horizontal directional solidification of Al-Rich Al-Cu alloys: Effect of thermal parameters, primary dendrite arm spacing and Al₂Cu intermetallic phase

Abstract

In this work, the effect of the growth rate (V_L) and cooling rate (T_R), primary dendritic arm spacing (λ₁) and Al₂Cu intermetallic phase on the microhardness was investigated during transient horizontal directional solidification of Al-3wt%Cu and Al-8wt%Cu alloys. Microstructural characterization of the investigated alloys was performed using traditional techniques of metallography, optical and SEM microscopy and X-Ray diffraction. The microhardness evolution as a function of the thermal and microstructural parameters (V_L, T_R, and λ₁) was evaluated using power and Hall-Petch type experimental laws, which were compared with other laws in the literature. In order to examine the effect of the Al₂Cu intermetallic phase, microhardness measurements were performed in interdendritic regions. Finally, a comparative analysis was performed between the experimental data of this work and theoretical models from the literature that have been proposed to predict primary dendrite arm spacing, which have been tested in numerous works considering upward directional solidification.