D019-Mg3In stable structure in Mg-In alloy

The stable D019-Mg3In structures can formed in the matrix of Mg-In alloy. The microstructural feature of Mg-In binary alloy is the overlapping configurations along the 0001α direction among multiple sets of D019-Mg3In structures, as the double-hexagons and multiple-hexagons shown in the schematic diagram. [Display omitted] •The solid solution indium atoms form a D019-Mg3In order structure.•D019-Mg3In structure is relatively stable in α-Mg matrix.•Four sets of D019-Mg3In structures are located in the different Mg-sublattice. In this study, Mg-3.0 wt% In binary alloys were solution treated at 420 °C and aging treated at 200 °C. To understand clearly the microstructural characteristics, the alloys were characterized by atomic-scale high angle annular dark field scanning transmission electron microscopy. It is found that a hitherto unreported D019-Mg3In order structure is formed in α-Mg matrix. With a hexagonal lattice (a ≈ 0.641 nm and c ≈ 0.521 nm), the D019-Mg3In structure is relatively stable and fully coherent with α-Mg matrix. Solid solution indium atoms have four categories of optional positions of Mg-sublattice, leading to the formation and co-existence of four sets of D019-Mg3In structures in α-Mg matrix. With aging time prolonged, a high concentration of D019-Mg3In structures results in several combined configurations of two or more sets of D019-Mg3In structures in Mg-In binary alloy.