The heterogeneous microstructure in an Al-Zn-Mg-Cu-Sc-Zr alloy produced by selective laser melting

Abstract

Fully dense and crack-free Al-Zn-Mg alloys with Sc and Zr additions were successfully fabricated by selective laser melting. The microstructures of as-built alloys with different Sc and Zr additions were characterized by scanning electron microscopy and transmission electron microscopy. The microstructure was composed of coarse columnar grains without Sc and Zr additions. In contrast, a fine heterogeneous microstructure, consisting of equiaxed grains at the bottom of the melt pool and columnar grains in the remaining volumes, was formed by adding 0.6 wt.% Sc and 0.26 wt.% Zr. In addition, a high density of precipitates was identified as η’ and I-phases that were distributed at grain boundaries and inside grains.