Abstract
In this work, bulk deposits of a Sc modified Al-Mn-Fe-Si alloy were prepared by selective laser melting (SLM), and the microstructural characteristics and tensile properties of the deposits were analyzed. The as-deposited sample presented a multiscale microstructure consisting of epitaxial columnar grains with width of 30–140 μm, in which there exist α-Al dendrite arrays with average primary dendrite arm spacing of 0.34 μm, and interdendritic nanoscale α-Al + Al6(Mn,Fe) divorced eutectic. After an aging treatment, Al6(Mn,Fe) transformed into Al12(Mn,Fe)3Si, and its morphology gradually evolved from skeleton into particle. Meanwhile, needle-like AlMnSi precipitated and grew up in the α-Al dendrite trunk. The ultimate tensile strength increased from 349 ± 9 MPa in the as-deposited state to 430 ± 3 MPa after aging at 300 °C. However, it dropped to 358 ± 1 MPa when the aging temperature increased to 350 °C. The addition of Sc caused precipitation strengthening of secondary Al3Sc after aging treatment, but the grain refinement effect of primary Al3Sc was inhibited since Sc tended to segregate at the frontier of the Mn-containing pre-precipitates.
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