Characterizations of micro-nano structure and tensile properties of a Sc modified Al-Mn alloy fabricated by selective laser melting

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 mu m, in which there exist alpha-Al dendrite arrays with average primary dendrite arm spacing of 0.34 mu m, and interdendritic nanoscale alpha-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 alpha-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 degrees C. However, it dropped to 358 +/- 1 MPa when the aging temperature increased to 350 degrees 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.

Automated summary

In this study, bulk deposits of a Sc modified Al-Mn-Fe-Si alloy were prepared by selective laser melting (SLM) and analyzed for microstructural characteristics and tensile properties. After aging treatment, the ultimate tensile strength increased, but decreased as the aging temperature increased. The deposits exhibited a multiscale microstructure consisting of alpha-Al dendrite arrays and non-dendritic eutectic structures.