Examination of Thermal Parameters, Primary Dendritic Spacings and Microhardness of a Horizontally Solidified Al-Cu-Mg Ternary Alloy

Abstract

In this paper, the Al-3wt.%Cu-0.5wt.%Mg alloy was grown by the transient horizontal directional solidification method in a water cooled stainless steel chill. A temperature monitoring system in the metal was used and the registered time-temperature data during the solidification process were applied to determine tip growth rates (VL) and cooling rates (TR) which have been correlated with both primary dendrite arm spacings (λ1) and Vickers microhardness (HV). Characterization techniques by optical and scanning electron microscopy (OM and SEM) were employed and the observed microstructures show an Al-rich dendritic matrix (a-Al) and θ (Al2Cu) and S (Al2CuMg) intermetallic phases within the interdendritic regions. Power and Hall-Petch type experimental equations were proposed to describe the HV profile as a function of the thermal and microstructural parameters (VL, TR, and λ1). In order to investigate the effect of the Mg alloying, a comparative analysis was also performed between the experimental values of this article and the results of previous studies carried out with the Al-3wt.%Cu binary alloy.