Abstract

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 °C for 19 h. β' and LPSO structures interconnected with each other via two spatial interaction types during aging treatment, contacting with each other directly or being separated by α-Mg layers. Novel rectangular and rhombic precipitates forming during aging treatment are identified as Gd3Y compound, which are observed for the first time by HAADF-STEM. Composite strengthening of LPSO, β' and Gd3Y precipitates contributes to a significant strengthening effect on the alloy.

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