The atomic structure of {10 $$\bar{{\bf{1}}}$$1 ¯ 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.

Ti(C, N)‐based cermet materials represent the best choice of materials for the manufacturing industry and military products. In this study, we use cubic β‐cobalt(β‐Co) as the binder phase to strengthen constructed cermets. At the same time, to optimize the microstructure, (Ti, W, Mo, Ta) (C, N) powders are added to form two kinds of core‐rim morphologies. Here, β‐cobalt powders with face‐centered cubic structures are obtained by the solid‐phase reaction of high‐energy ball milling. A solid‐phase chemical reaction and a carbothermic reduction‐nitridation method are used to prepare the (Ti, W, Mo, Ta) (C, N) powders. In our process, first we mix the cobalt and (Ti, W, Mo, Ta) (C, N) powders; then we press the powder mixtures into rectangular samples and sinter them in a pressure sintering furnace to obtain Ti(C, N)‐based cermets with two kinds of core‐rim structure, that is, black core/white rim and white core/gray rim. The results show that the new cermets demonstrate excellent toughness and performance.

Mg–3Al–1Zn alloy extruding rods were subjected to rotary forging at temperatures ranging from room temperature to 723 K. The effect of rotary forging on formability, microstructures, and hardness of the samples was investigated. Compared to common forging, rotary forging appeared to significantly promote formability at elevated temperatures, especially at 673 K and 723 K. Dynamic crystallization occurred in both samples prepared at these two temperatures, whereas newly generated grains in the 673 K were much finer. A special tilted basal texture was discovered in both samples, exhibiting strong anistropy, and the hardness in the cross section increased from the center to the edge of the samples.

Rotary forging was conducted for TA2 titanium samples with initial forming temperatures ranging from room temperature to 923 K. The microstructure of the samples was examined by using electron back-scattered diffraction and X-ray diffraction. The results indicate that rotary forging remarkably enhanced the formability of TA2 titanium and took a notable grain refinement effect over the whole temperature range. The theoretical calculation results indicate that enough working heat was generated during the early deformation stage to raise the temperature of the sample to above the dynamic recrystallization temperature. The deformation of titanium during rotary forging can be roughly divided into two stages as dislocation slip stage and the dynamic recrystallization stage.

Compressive tests were performed to homogenized AZ31 magnesium alloy samples to various strains and fracture at room temperature (RT). The microstructure of the samples was observed by optical microscope(OM); the twin types were examined by electron backscattered diffraction (EBSD) technique; and the fracture surfaces were detected by scanning electron microscope (SEM). The fracture mechanism was discussed by considering the interaction among basal slip, twinning and interface motion. It was considered that basal slip and {10 1 2} twinning work together during deformation. Basal slip may result in the potential origin of fracture at grain boundaries (GBs); while the interface of {10 1 2} twins may become the favorable source of fracture across the grains.

The atomic motions in the twinning deformation of hexagonal close-packed (HCP) crystals was investigated at the atomic scale by using the giant atomic clusters (GACs) induced model, aimed at deepening the understanding to the twinning mechanism. It is found that the twin boundaries are composed of gradually oriented GACs with their orientation between the matrix and the twin, and the GACs can transfer their rotation under adequate stress, which supplies a reasonable explanation for the occurrence of twinning. These findings are relevant for understanding the underlying origin behind many intriguing phenomena in the HCP crystals.