Fig. 1 〈11-20〉α view of typical LPSO structures: a 18R, b 14H, c the transformation from hcp structure to fcc SU. The fcc SUs in a-b are highlighted by grey box. The transformation of hcp structure to fcc needs two processes. One is the stacking sequence change by the movement of a partial dislocation, and the other is segregation of RE and M solute atoms to SU

Fig. 2 Schematic diagram of two possible mechanisms for LPSO formation in crystalline Mg matrix: a element segregation-assisted dislocation dissociation, b chemical modulation/cluster forms first without structural change

Fig. 3 Preparation procedure of 3DAP sample: a inverse pole figure (normal direction) mapping of Mg sample by EBSD, b selected grain as indicated in a with arrow, c cutting with FIB, d mounting to silicon stage, e needling, f test and obtain the result of element distribution

Fig. 4 Element distribution of Gd and Zn solute atoms in Mg matrix for Mg-Zn-Gd alloy: a as-cast sample, b aged at 280 °C for 1 h

Fig. 5 Enlarged view of rectangular area in Fig. 4b: a element mapping of Mg, Zn and Gd, and Mg atoms is shown by pink dots, b corresponding concentration profile

Fig. 6 Radius distribution function between Zn and Gd pairs in Mg matrix for different ageing times

Fig. 7 Interatomic distance for different nearest neighbours in hcp structure [44]

Fig. 8 Transforming front of the SU in the left side in Fig. 4b indicated by double arrow: a Mg mapping, b Gd mapping, c Zn mapping, d element distribution along the arrow in c. View direction is [0001]α

Fig. 9 Superimposition of detector event histogram and stereographic projection of hcp structure