Complex wrought magnesium-based alloys suffer from poor ductility, strong yield asymmetry, and lower than desired fatigue performance. These unfavourable properties are exacerbated by the heterogeneity of the microstructure and strong texture forming in Mg alloys during conventional thermo-mechanical processing. For the user, severe plastic deformation (SPD) increases flexibility in tailoring the microstructures and selecting the properties to be emphasized in wrought Mg alloys. The effect of SPD by hot multiaxial forging and equal channel angular pressing on the formation of fine grain microstructure and on resultant mechanical properties is discussed. It is demonstrated that SPD is capable of substantial enhancement in ductility and tensile strength which gives rise to concurrent improvement of both low- and high-cycle fatigue properties. The main message of this overview is that the full potential for improving fatigue performance of Mg alloys can be taken advantage of by way of comprehensive understanding the role of the individual effects associated with the SPD-induced microstructures and textures.

First-principles shear tests were performed on pure Mg, Mg–Li, Mg–Ca, Mg–Al, Mg–Sn, Mg–Ag, and Mg–Zn models to investigate the mechanical and chemical effects of the solute elements on the generalized stacking fault energy (GSFE) of Mg. The mechanical effect increased the unstable stacking fault energy (USFE), independent of the kind of solute element tested. The intensity of the mechanical effect was explained by the average distance between a solute atom and the surrounding Mg atoms, not by a difference in atomic radius between a solute atom and a Mg atom. In contrast, the chemical effect on the USFE was complicated, and the chemical effects of Ag and Zn were lower than expected from their electronegativity. Also, the chemical effect increased the USFE for the Li addition, but it decreased the USFE for the Ca addition although the electronegativity of Li is almost the same as that of Ca.

A melt-spun Mg-1.5%wtCa-6wt%Zn alloy was analyzed by means of transmission electron microscopy, energy dispersive X-ray spectroscopy, and scanning transmission electron microscopy. The as-solidified alloy exhibited both spherical matrix precipitates and elongated precipitates at the grain boundaries (grain-boundary films). After heat treatment, the alloy showed faceted precipitates (cuboidal shape), mostly on dislocations. It was found that the observed precipitates are the same compound, Ca2Mg6Zn3. As there was no crystallographic data for this compound in the literature, its crystal structure was investigated by comparison of experimental and simulated selected-area electron-diffraction patterns and high-resolution electron microscopy images. This study indicated that Ca2Mg6Zn3 is a trigonal compound with space group P31c and lattice parameters a = 0.97 nm, c = 1.0 nm.