Microstructure and mechanical properties of a novel Sc and Zr modified 7075 aluminum alloy prepared by selective laser melting

摘要

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/mm(3), the average grain size was 2.6 mu m, which is only 9.8% of the size of samples fabricated at 44 J/mm(3). 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/mm(3) were 621 MPa and 1.85 GPa, which are respectively 129.6% and 98.4% of the specimen fabricated at 44 J/mm(3).