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In this paper, the corresponding densification, microstructure, precipitate phase and mechanical properties of Al-14.1Mg-0.47Si-0.31Sc-0.17Zr fabricated by selective laser melting were detailly investigated. The experimental result shows that the densification of SLM specimens increased first and then decreased with energy density. Even at the same energy density, the relative densities of the samples are also different, and the printed sample has a high densification under the condition of low laser power and scanning speed. Two typical microstructures (fine grain zone and coarse grain zone) were formed inside the printed samples due to the formation of Al 3 (Sc, Zr) particles (coherent with the Al matrix) during the solidification process of SLM. As fabricated at 200 W and 500 mm/s, the average grain size of the SLM sample is 2.07 (Y-Z plane) and 1.72 μm (X–Y plane), and the maximum values of nano-hardness and tensile strength were 2.19 GPa and 510 MPa, respectively. The mechanical properties increased due to the combined effect of fine grain strengthening and dispersed distribution of precipitates in Al matrix. With a low density (2.537 g/cm3) and high tensile strength, the components fabricated by this alloy have more extensive spreading values and prospects for applying due to the excellent mechanical performance. [ABSTRACT FROM AUTHOR]

A novel Sc- and Zr- modified 7075 Al alloy with a low microalloying content (0.4 wt% Sc and 0.25 wt %Zr) was designed and the influence of process parameters on the microstructure and mechanical properties of selective laser melting (SLM) samples was systematically analyzed. As the SLM energy input increased, the relative density of block specimens first increased before plateauing. At a high energy density, crack defects disappeared, and the average grain size significantly decreased. For the specimen fabricated at 375 J/mm3, the average grain size was 2.6 μm, which is only 9.8% of the size of samples fabricated at 44 J/mm3. Due to fine grain strengthening, the mechanical properties of the printed specimens were remarkably improved, but the high energy input softened the matrix. Due to these two opposing effects, the compressive strength and nano-hardness of specimens fabricated at 375 J/mm3 were 621 MPa and 1.85 GPa, which are respectively 129.6% and 98.4% of the specimen fabricated at 44 J/mm3. [ABSTRACT FROM AUTHOR]