Yan Yang

Dendrite spatial orientation dominates the geometry of liquid channels and interlocking states of dendritic skeletons, yet quantitative correlations between crystallographic orientation and mushy zone seepage performance remain insufficiently clarified. In this study, a phase-field lattice-Boltzmann method is applied to numerically simulate dendrite growth of Mg-6 wt. % Gd alloy under varying dendrite orientations. Three hierarchical simulation frameworks (single dendrite, dual interacting dendrites, and a multi-dendrite network) are constructed to decouple and quantify the independent and synergistic effects of dendrite orientation and solidification conditions (undercooling and flow intensity) on dendritic morphology, solid fraction, fractal dimension, and interdendritic permeability. Results demonstrate that the solid fraction acts as the primary controlling factor of permeability, while the dendrite orientation functions as a secondary critical regulator by modifying channel tortuosity and intergranular interlocking modes. For the dual-dendrite systems, identical orientation induces severe face-to-face dendrite interlocking and yields 15%–20% lower permeability than symmetric staggered orientation; a universal permeability minimum occurs at orientation angles of 25°–35° due to maximized channel tortuosity. In the multi-dendrite networks, uniformly aligned dendrites form dense narrow flow channels with the lowest permeability, while a dispersed orientation distribution optimizes inter-channel connectivity and improves overall seepage capacity. This study clarifies the regulatory role of dendrite orientation on the seepage capacity of the mushy zone and provides a microscopic explanation for the differences in liquid feeding capacity under different grain orientation conditions.

Magnesium matrix composites formed by incorporating ceramic particles into a magnesium alloy matrix can effectively leverage the complementary properties of the matrix and reinforcement. This approach significantly enhances the mechanical properties of the material at both room and elevated temperatures, offering a viable solution to the inherent limitations of Mg alloys, such as insufficient absolute strength, stiffness, and poor heat resistance. This article reviews the latest research progress in the field of ceramic particle-reinforced magnesium matrix composites in recent years. First, the current research status of magnesium matrix composites reinforced with different types of ceramic particles is comprehensively summarized. Subsequently, it provides a summary and in-depth analysis of the principles, key technologies, and microstructural characteristics of both mainstream and emerging preparation processes, and discusses their advantages and disadvantages. Finally, the challenges in current research are analyzed, and future cutting-edge directions for developing high-performance ceramic particle-reinforced magnesium matrix composites are discussed.

Pre-aged Mg-6Zn-1Gd-1Er alloy is a novel rapid aging hardening Mg alloy, and studying its hot deformation behavior has an important role in promoting the development of lightweight alloy materials. To study this, the flow stress curves of pre-aged Mg-6Zn-1Gd-1Er alloy at 180–380 °C and 10⁻³−10 s⁻¹ were obtained by isothermal compression tests. The constitutive equations of the medium-high temperature deformation (MHTD) and the low-temperature deformation (LTD) were established, and their activation energies were 155.78 kJ mol⁻¹ and 178.00 kJ mol⁻¹, respectively. Based on the constitutive equation analysis, the glide and climb of dislocations and the cross-slip of dislocations was the deformation mechanism during MHTD and LTD, respectively. In order to determine the appropriate hot processing parameters, the hot processing map of the pre-aged Mg-6Zn-1Gd-1Er alloy under 0.2–0.8 strain was constructed based on the dynamic material model. The hot processing maps indicate that this pre-aged alloy at low temperature (180–230 °C) and high strain rates (1–10 s⁻¹) mainly occurs flow instability, and the optimal hot processing window appears at a 330–380 °C and 10⁻³ to 10⁻² s⁻¹ range. Furthermore, the deformation mechanism of the stable domain with high power dissipation efficiency in the hot processing map was continuous dynamic recrystallization, discontinuous dynamic recrystallization, and particle-stimulated nucleation mechanisms.

Effects of annealing temperature on the microstructure and mechanical properties of cold-rolled LZ91 alloy are investigated. The results indicate that LZ91 alloy is composed of α-Mg, β-Li, MgLiZn and MgLi₂Zn phases. The recrystallization of the cold-rolled alloy is completed when annealing at 125°C and a large number of fine equiaxed grains with an average grain size of 3 µm is formed. The cold-rolled LZ91 alloys annealed at 125°C have the optimized comprehensive mechanical properties with the elongation, ultimate tensile strength and microhardness of 56.1%, 157 MPa and 51.2 HV, respectively. With the further increase in annealing temperature, the grain size begins to coarsen, which leads to the decrease in strength and ductility of the alloy.

The effect of Ca addition on the microstructure, mechanical properties, and corrosion behaviors of the extruded Mg–7Li–3Al alloys was investigated. The results showed that the extruded Mg–7Li–3Al–xCa alloys consisted of α-Mg (hcp) + β-Li (bcc) matrix phases and Al₂Ca. With increasing Ca content, the amount and morphology of the Al₂Ca phase changed significantly. The grains of the extruded Mg–7Li–3Al–xCa alloys were refined by dynamic recrystallization during the extrusion process. The tensile tests results indicated that the extruded Mg–7Li–3Al–0.4Ca alloy exhibited favorable comprehensive mechanical properties; its ultimate tensile strength was 286 MPa, the yield strength was 249 MPa, and the elongation was 18.7%. The corrosion results showed that this alloy with 0.4 wt.% Ca addition exhibited superior corrosion resistance, with a corrosion potential E_corr of −1.48742 V_VSE, attributed to the formation of protective Al₂Ca phases.