The atomic structure of {10 2} twin boundary (TB) from a deformed Mg-3Al-1Zn (AZ31) magnesium alloy was examined by using high-resolution transmission electron microscopy (HRTEM). By comparing the lattice structure of TB with the previously established model, a kind of special atomic combinations, here named primitive cells (PCs), were discovered at the TB. The PCs reorientation induced mechanism of twinning in hexagonal-close-packed (HCP) crystals was hence verificated. Meanwhile, the relationship between the misorientation of adjacent layers of PCs and the width of TB was discussed. The verification of the mechanism clarifies the twinning mechanism in HCP crystals and opens up opportunities for further researches.

A magnesium alloy containing Al2Y particles was successfully fabricated by changing the content of Al in the Mg-6Y alloy melt. Its microstructure and mechanical properties were subsequently characterized. The results show that two types of Al2Y particles were discovered in the Mg-6Y-xAl (x = 0.5–5) alloys, which are namely the polygonal particles in the pre-precipitated phase and the discontinuous network of particles in the eutectic phase. With an increase in Al content, the amount of pre-precipitated Al2Y increases and the eutectic decreases gradually. When the Al content is 5 wt %, Al2Y particles are almost all in the pre-precipitated phase in the Mg-6Y alloy. After hot extrusion, the YA65 alloy could be regarded as the Mg master alloy that contains Al2Y particles with heterogeneous nucleation capability or Al2Y particle-reinforced magnesium matrix composites. The tensile strength of the as-extruded magnesium alloy is significantly improved at ambient temperatures.

In this study, the microstructure of Ti(C, N)-based cermet was improved by adding β-cobalt (face-centered cubic) and (Ti, W, Mo, Ta)(C, N) solid solution powder to prepare micro-nano Ti(C, N)-based cermet powder. In order to improve the comprehensive properties of the material. Firstly, the Co powder with face-centered cubic structure was obtained by the solid-phase reaction of high-energy ball milling, and its plastic deformation resistance was higher than that of Co powder with dense hexagonal structure. Secondly, The powder of (Ti, W, Mo, Ta)(C, N)solid solution was obtained by mechanical alloying and high-temperature carbonization under the atmosphere of N2. And the two were applied to the micro-nano Ti(C, N)-based cermet powder, and finally the properties of cermet powder were compared with that of ordinary cermet powder. The results show that the microstructure of micro-Ti(C, N)-based cermet powder prepared in this study is a double-core rim structure, that is, the structure of black core white rim and gray core white rim. This structure can effectively prevent crack of the expansion. The strength and toughness of cermet materials are greatly improved, which is beneficial to the improvement of comprehensive properties of cermet materials.

A cast Mg–3Gd–0.6Zr alloy with microscale [Formula: see text] growth twins was designed successfully. After the alloy was annealed at 350°C for 1 h, the volume fraction of the growth twins was increased by approximately 120%. Gd solute atoms segregated on both sides of twin boundaries and facilitated their formation in the as–cast alloy. The formation mechanism of [Formula: see text] growth twins in the as–cast alloy was discussed in five aspects: the supersaturation of Gd solute atoms, the segregation ability of Gd, the composition of Gd, the nucleate sites of growth twins, and the total energy of the system. The growth twins elicited remarkable toughening effect but a moderate strengthening effect on the alloy.