Graphene, as the reinforcing phase of magnesium matrix composites, can effectively improve the material strength, elastic modulus, and other properties. However, the random distribution of graphene in the matrix (i.e., random orientation angle) leads to different reinforcement effects on the matrix. To gain a deeper understanding of the impact of monolayer graphene (1LG) with varying orientation angles on the properties of Mg-9Al-1Zn (AZ91 (wt.%)) magnesium alloy, molecular dynamics (MD) simulations are employed to analyze the mechanical properties of AZ91/1LG composites under uniaxial tension. The simulation results show that Young's modulus and tensile strength of AZ91/1LG composites decrease gradually with the increase of the orientation angle of the 1LG. The Young's modulus and tensile strength of AZ91/1LG composites can be improved by the 1LG orientation angle of 0°~10°, where the two are enhanced by 21.7% and 19.7% respectively, at an orientation angle of 0°. However, the Young's modulus and tensile strength of 1LG are decreased for orientation angles of 20°~90°. Atomic structure evolution analysis revealed that the deformation mechanism of AZ91/1LG nanocomposites mainly depended on the load transfer ability of 1LG with different orientation angles, the bonding ability with AZ91 magnesium alloy matrix and the change of dislocation density. By fitting the formula to the tensile strength of AZ91/1LG composites with different orientation angles of 1LG, it is found that the simulated data of the AZ91/1LG composites containing a 1LG has a maximum relative error of about 10% concerning the fitted empirical formula to calculate the data. The maximum relative error for AZ91/1LG composites containing multiplate 1LG with different orientation angles is 7%. In addition, the interaction between graphene and dislocations in AZ91 magnesium matrix was further explained by transmission electron microscopy (TEM) and phase-field-crystal (PFC) simulation. It can provide some technical guidance for the experimental process design of AZ91/1LG composites.

Magnesium alloy is widely used in the aerospace field due to its low density, high specific strength, high damping and good thermal conductivity. However, its low elastic modulus limits its reliable application in large thin-walled components. Aiming at the problem to improve the modulus properties of magnesium-based materials, this paper briefly introduces the main factors affecting the modulus of the alloy, compares the advantages, disadvantages and application scope of relevant calculation models such as equal stress-strain model, rule of mixture, Halpin-Tsai model and two-phase composite model, summarizes the current situation and progress of the research on the modulus properties of magnesium-based materials, and reviews the two major ways of modulus improvement of magnesium-based materials and the mechanism of performance improvement. Based on the integrated computational material engineering, the integrated development strategy of high-strength and high-modulus magnesium-based materials for atomic-lattice scale analogy high-modulus aluminum alloy development and machine learning assisted optimization experimental design is proposed.

Mg-Zn-based alloys have been widely used in computer, communication, and consumer (3C) products due to excellent thermal conductivity. However, it is still a challenge to balance their mechanical performance and thermal conductivity. Here, we investigate microstructure, mechanical performance, thermal conductivity and metal fluidity of Mg-5Zn (wt.%) alloy after Cu alloying by experimental and simulation methods. First, Mg-5Zn alloy consist of α-Mg matrix and interdendritic MgZn phases. As the Cu content increases, however, MgZn phases disappear but intragranular Mg₂Cu and interdendritic MgZnCu phases appear in Mg-5Zn-Cu alloys. Besides, the grain size of α-Mg phase is refined and the volume fraction of MgZnCu phase increases as the Cu content increases. Second, Cu addition is found to improve thermal conductivity of Mg-5Zn alloy remarkably. Especially, Mg-5Zn-4Cu alloy exhibits the best thermal conductivity of 124 W/(m·K), which is mainly due to the significant reduction in both solid solubility of Zn in the α-Mg matrix and lattice distortion of α-Mg matrix. Moreover, a stable crystal structure of MgZnCu phase also contributes to an increased thermal conductivity based on first principles and molecular dynamics simulations. Third, Cu addition simultaneously enhances strength and ductility of Mg-5Zn alloy. Tensile yield strength and elongation of Mg-5Zn-6Cu alloy reach 117 MPa and 18.0 %, respectively, which is a combined result of refinement, solution, second phase, and dislocation strengthening. Finally, combined with a phase field simulation, we found that Cu addition enhances metal fluidity of Mg-5Zn alloy. On the one hand, Cu alloying not only delays dendrite growth but also prolongs solidification time. On the other hand, MgZnCu phase stabilizes the dendrite growth of the α-Mg phases by reducing energy consumption during solidification of liquid metal. This work demonstrates that Cu alloying is an ideal strategy for synergistically improving the thermal conductivity, mechanical performance and metal fluidity of Mg-based alloys.

The regulation of sintering temperature in spark plasma sintering enables the achievement of grain refinement, phase control, and performance enhancement in the preparation of AZ91D magnesium alloy. This study investigates the influence of sintering temperature on microstructural evolution and mechanical properties of the AZ91D alloy. Microstructural analysis was conducted using scanning electron microscopy, electron backscatter diffraction, and X-ray diffraction. Microscopic structures and mechanical behaviors were examined through hardness and tensile tests. Elevated sintering temperatures resulted in reduced secondary phase content, leading to a decrease in mechanical performance. The alloy exhibited optimal mechanical properties at 320℃. The nanoparticle coarsening process and particle evolution during sintering were simulated using phase field methods. By optimizing the sintering temperature, precise control over microstructural and textural evolution can be achieved, facilitating the attainment of desired hardness levels and mechanical properties.

This work studied the microstructure, mechanical properties and damping properties of Mg_95.34Ni₂Y_2.66 and Mg_95.34Zn₁Ni₁Y_2.66 alloys systematically. The difference in the evolution of the long-period stacked ordered (LPSO) phase in the two alloys during heat treatment was the focus. The morphology of the as-cast Mg_95.34Ni₂Y_2.66 presented a disordered network. After heat treatment at 773 K for 2 hours, the eutectic phase was integrated into the matrix, and the LPSO phase maintained the 18R structure. As Zn partially replaced Ni, the crystal grains became rounded in the cast alloy, and lamellar LPSO phases and more solid solution atoms were contained in the matrix after heat treatment of the Mg_95.34Zn₁Ni₁Y_2.66 alloy. Both Zn and the heat treatment had a significant effect on damping. Obvious dislocation internal friction peaks and grain boundary internal friction peaks were found after temperature-dependent damping of the Mg_95.34Ni₂Y_2.66 and Mg_95.34Zn₁Ni₁Y_2.66 alloys. After heat treatment, the dislocation peak was significantly increased, especially in the alloy Mg_95.34Ni₂Y_2.66. The annealed Mg_95.34Ni₂Y_2.66 alloy with a rod-shaped LPSO phase exhibited a good damping performance of 0.14 at ε=10⁻³, which was due to the difference between the second phase and solid solution atom content. These factors also affected the dynamic modulus of the alloy. The results of this study will help in further development of high-damping magnesium alloys.

We investigate the variation induced in long-period stacking ordered (LPSO) structures, dynamic recrystallization (DRX), and mechanical performance of hot-extruded Mg₈₉Y₄Zn₂Li₅ alloys fabricated at different extrusion speeds (V_e = 0.4, 0.8, 1.0, 1.2 mm/s) and die angles (α = 30°, 60°, 90°) under 400 °C, the dissolution and reprecipitation of 14H LPSO structure accompanied by DRX process are then clarified in detail. Upon all extrusion conditions, the block 18R LPSO structures elongate in the extrusion direction, while the lamellar 14H LPSO structures dissolve under the deformation strain. In addition, due to discontinuous and continuous DRX mechanisms, all hot-extruded alloys have a full DRX microstructure consisting of equiaxed recrystallized grains, but the DRX grain size reduces when both extrusion speed and die angle decrease. Note that, in the interior of DRX grains, thin LPSO lamellae mixing 14H, 18R and 24R structures nucleate and dynamically precipitate due to the dissolution of the original lamellar 14H LPSO structures. Furthermore, the hot-extruded Mg₈₉Y₄Zn₂Li₅ alloy becomes stronger as decreasing of the extrusion speed and die angle, whereas the ductility remains nearly constant. Finally, the hot-extruded Mg₈₉Y₄Zn₂Li₅ alloy achieves an excellent strength-ductility balance at a relatively low extrusion speed (0.4 mm/s) and small die angle (30°) mainly due to the elongated 18R LPSO structure, fine and full DRX microstructure, thin mixed LPSO precipitates in the DRX grains, twins and dislocations.