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Banded and discontinuous eutectic microstructures were found in melt quenched ribbons and laser melted single tracks of an Al-3%wt Er alloy, respectively. The bands occurring in ribbons are made of alternate primary α-Al phase and eutectic. Their formation is well described by the Han-Trivedi model for banding in alloy solidification. Microstructure fluctuations between fibrous and discontinuous eutectic are seen in laser melted single tracks on the same length scale of bands due to change in local temperature gradient. Overall, various transitions in phase morphology are found in thin zones of material constituting a valuable guideline for interpretation of the solidification mechanism. Nano-indentation tests show that the fine microstructures induce substantial hardening.

Powder bed additive manufacturing technologies gained much attention in past years not only thanks to design freedom but also because of the peculiar microstructures and mechanical properties that can be obtained thanks to the extremely high cooling rate. However the phenomena that arise during the laser scanning are not yet deeply understood. In this work the effect of the main building parameters and of powder properties on the shape, the microstructure and the properties of Al-based LPBF single scan tracks was evaluated. The experiments were carried out with three different powders in order to understand of the effect of the material thermo-physical properties on the consolidation phenomena.