Precipitation in Mg–Nd–Y–Zr–Ca Alloy during Isothermal Aging: A Comprehensive Atomic‐Scaled Study by Means of HAADF‐STEM

This paper investigates into the precipitation behavior of Mg–2Nd–1Y–0.1Zr–0.1Ca (wt%) alloy during isothermal aging at 225°C, using atomic‐scale HAADF‐STEM. The precipitation sequence in Mg–Nd–Y–Zr–Ca is identified as follows: nucleation(β L   a n d   β H ) → needle‐like precipitates composed of β M , β′ T , and β C structures as repetitive units → β 1  → equilibrium β. From an engineering point of view, the atomic‐size precipitates that distribute uniformly have a significant strengthening effect. In addition, the present study discusses three findings concerning the novel structures observed in the alloy: two types of interaction between needle‐like precipitates are observed; the previously reported β″ structure is doubted according to the analysis of the defects characterized from [ 11 2 ¯ 0 ] Mg ; calcium is observed to be enriched in β1 precipitates and along grain boundaries.