First-principles study of coherent interfaces of Laves-phase MgZn2 and stability of thin MgZn2 layers in Mg-Zn alloys.

The β 1 ′and β 2 ′ are important precipitates in Mg-Zn alloys. Two types of precipitates both are composed of MgZn 2 , but the orientation relationships of MgZn 2 with the α-Mg matrix in two precipitates are different. To understand the properties of β 1 ′and β 2 ′, we use the first-principles method to perform a systematical investigation of coherent interfaces of β 1 ′/α-Mg and β 2 ′/α-Mg. Here, we present exhaustive analysis of the structure and stability for these interfaces, and find that the interfacial energy is highly dependent on the average coordination of interfacial structures. Furthermore, we find that the MgZn 2 slab in matrix with [11 2 ¯ 0] MgZn2 //[0001] α , (0001) MgZn2 //(11 2 ¯ 0) α orientation relationship (OR1) is less stable than that with [11 2 ¯ 0] MgZn2 //[10 1 ¯ 0] α , (0001) MgZn2 //(0001) α orientation relationship (OR2), which can explain that the β 2 ′ plate shape precipitates that are frequently observed in Mg-Zn alloys comply with OR2 instead of OR1. [ABSTRACT FROM AUTHOR]