Local atomic structures of Gd and Zn atoms in extruded Mg-Gd-Zn alloys

Minor addition of Gd and Zn can significantly improve the mechanical properties of extruded Mg-1 wt.%Gd-xZn (x = 0, 0.5, 1 wt.%) alloys. However, how they modify the structure of alloys remains elusive. By using x-ray absorption fine structure, we found that Zn atoms tend to bond with Gd and the 0.5 wt.% Zn addition greatly reduces the coordination number (CN) of Gd atoms, forming an enhanced double solid-solution strengthening. Whereas, 1 wt.% Zn not only increases the CNs of Zn and Gd but also promotes the formation of minor Mg3Zn3Gd2 phase. Compared with the grain refinement strengthening, it is found that the solid solution strengthening is not a dominant factor. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

Minor addition of Gd and Zn can significantly improve the mechanical properties of extruded Mg-1 wt.%Gd-xZn (x = 0, 0.5, 1 wt.%) alloys. The addition of Zn tends to bond with Gd, reducing the coordination number of Gd atoms at 0.5 wt.% Zn, forming an enhanced double solid-solution strengthening. On the other hand, 1 wt.% Zn increases the coordination numbers of Zn and Gd, as well as promotes the formation of minor Mg3Zn3Gd2 phase. Compared with grain refinement strengthening, solid solution strengthening is not the dominant factor in this case.