Chemistry of nanoscale precipitates in Mg-2.1Gd-0.6Y-0.2Zr (at.%) alloy investigated by the atom probe technique

The precipitation sequence of a Mg-2.1Gd-0.6Y-0.2Zr (at.%) alloy at 200 °C was investigated by transmission electron microscopy (TEM), and the chemical compositions of the precipitates observed in different stages of the sequence were analyzed by the three-dimensional atom probe (3DAP) technique. The precipitation sequence is described as supersaturated solid solution (SSS) → β″ (D019 Mg3X) → β′ (bco Mg15X3) → β phase (Mg5X). There are structural similarities in each phase and the phase evolution occurs continuously by decreasing the rare earth content when β″ transforms to β′.