Atomic-scale observation on the precipitates in various aging stages of Mg-Gd-Y-Cu alloy

This paper reports a comprehensive investigation of long-period stacking ordered (LPSO) structures and precipitates in various stages of aging treatment in Mg96Gd2Y1Cu1(at%) alloy, using atomic-scaled Cs corrected high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM). 14H and 18R-LPSO structures coexisted in as-cast alloy, dissolved in solid solution state and reappeared after aging treatment. The aging peak hardness reached 147 HV at 200 degrees C for 19 h. beta' and LPSO structures interconnected with each other via two spatial interaction types during aging treatment, contacting with each other directly or being separated by alpha-Mg layers. Novel rectangular and rhombic precipitates forming during aging treatment are identified as Gd3Y compound, which are observed for the first time by HAADFSTEM. Composite strengthening of LPSO, beta' and Gd3Y precipitates contributes to a significant strengthening effect on the alloy. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study provides a comprehensive investigation of LPSO structures and precipitates in Mg-Gd-Y-Cu alloy during aging treatment, revealing the evolution of various structures in the alloy and identifying the formation of novel Gd3Y precipitates for the first time. The composite strengthening effect of LPSO, beta', and Gd3Y precipitates significantly contributes to the strengthening effect on the alloy.