Densification, microstructure and properties of Sc and Zr modified Al-Mn alloy prepared by selective laser melting

In this work, the selective laser melting (SLM) of Sc and Zr modified Al-Mn alloy was systematically investigated, with a particular emphasis on the density behavior, microstructure and mechanical properties. The process parameters were significantly impact on the relative density and the maximum relative density of SLM-processed Al-Mn-Sc-Zr specimens reached 99.8% at the optimized process parameters. With the reduction of energy density, the melting mode of melting pool changed from keyhole mode to conduction mode. At the high energy density, near-spherical pores were generated because of the evaporation of low melting alloy constituents. With the decreasing of energy density, irregular pores were generated, which was mainly caused by the insufficient energy input. The SLM processed Al-Mn-Sc-Zr showed a duplex grain microstructure consisting of regions of columnar grains and equiaxed grains. Good mechanical properties were reached in as-fabricated condition: tensile strength > 426 MPa and elongation to fracture > 18%. Besides, no significant anisotropy was found in the stress-strain behavior between horizontal and vertical building direction.