This study investigates the microstructure evolution and mechanical behavior of a laser-welded dissimilar joint between wrought AZ80 and cast AM60 magnesium alloys. Microstructure analysis revealed a distinct fusion zone (FZ) spanning 1.5 mm and a heat-affected zone (HAZ) measuring 550 µm in width adjacent to the AZ80 alloy. Meanwhile, the AM60 side showed no fusion-related structural changes. The FZ microstructure had a characteristic dendritic solidification pattern, with an average grain size around 20 µm. The welded joint exhibited mechanical performance comparable to that of the base materials, with a yield strength of 137 MPa, an ultimate tensile strength of 250 MPa, and an elongation of 5.9%. These properties resulted from precipitated phases within the FZ, strengthening the joint and the coarse-grained structure’s significant work-hardening ability. Digital image correlation (DIC) during tensile testing indicated that strain concentrated within the FZ due to its coarse microstructure. As deformation continued, the AM60 base material experienced plastic deformation, sharing the main strain burden with the FZ. In later stages, microcracks formed specifically at the FZ-AM60 interface. These microcracks coalesced, accelerating crack propagation and resulting in a main crack that caused the joint to fracture. These findings offer valuable insights into controlling failure mechanisms in dissimilar magnesium alloy welds.

Due to the poor plasticity and deformability, magnesium matrix composites are difficult to strengthen using traditional severe plastic deformation (SPD) processes. In this study, we applied a large deformation of 0.36 to SiC particles reinforced Mg-Zn-Ca (ZX50/SiCp) composites at room temperature via rotary swaging (RS). The RS process significantly increased the yield strength of the composite from 174.1 MPa after extrusion to 346.5 MPa after RS with ten passes, representing a 98% enhancement. The remarkable strengthening effect was primarily attributed to grain boundaries strengthening, dislocation strengthening and precipitation strengthening effects. The results indicated that the average grain size of the composite refined to 16 µm after ten passes, and a substantial number of deformation twins were developed in the host grains. The interactions between twin boundaries and precipitates as well as reinforcement particles blocked the twin growth, resulting in dense twin networks. With increasing strain, multiple twins developed to further refine the twin lamella. Furthermore, the activation of numerous dislocations developed dislocation arrays and the geometrically necessary dislocations (GNDs) density increased from 2.8 × 10¹⁴ to 7.2 × 10¹⁴ m^-2. In addition, dynamic precipitation occurred during the RS process, resulting in the formation of substantial nano-scale Mg-Zn second phases (average diameter ~70 nm). The severe shear strain during the RS process promoted the uniformly dispersion of reinforcement particles. These findings provide valuable insights into the fabrication and strengthening of magnesium matrix composites through the proposed RS process.

Magnesium (Mg) alloys have attracted considerable attention in the automotive and aerospace industries due to their exceptional lightness, high specific strength, and excellent castability. However, their susceptibility to fatigue failure poses significant challenges for the long-term service under cyclic loading. This review systematically explores the precipitation behavior in the representative rare-earth containing magnesium (Mg-RE) alloys and examines the critical role of precipitates in influencing fatigue behavior. The alloying elements and heat treatment play a pivotal role in affecting the precipitation behavior of the Mg-RE alloys. Notably, the β′, β″, and 14H long-period stacking ordered (LPSO) phases serve as primary strengthening precipitates in the Mg-Gd (Y), Mg-Nd, and Mg-RE-Zn based alloys, respectively. The size, quantity, and distribution of these precipitates can be finely controlled through the optimization of aging treatment parameters. Based on the fundamental principles for enhancing fatigue resistance, this review offers a detailed analysis of the effects of precipitates on fatigue behavior, addressing key aspects such as crack initiation, propagation, and fatigue failure under high-cycle fatigue (HCF) conditions. Besides, the effects of precipitates on the cyclic stress response, cyclic deformation characteristics, and fatigue life under low-cycle fatigue (LCF) conditions are systematically summarized. The influence of precipitates on fatigue behavior of Mg-RE alloys is primarily attributed to the mechanisms such as dislocation pinning, crack path deflection, precipitation strengthening, and the suppression of twinning. This review highlights the significance of precipitation behavior in optimizing fatigue resistance and provides valuable insights into future research directions for advancing Mg-RE alloys in the fatigue-critical structural applications.

Poor plasticity is an intrinsic disadvantage of magnesium (Mg) alloys, which limits their wide application at room temperature. Alloying is an accepted method to tune the plastic deformation mode and improve plasticity. However, the effect of solute atoms on the activation of different dislocations is still unclear and has rarely been systematically investigated in Mg alloys. In this work, the formulations of Peierls-Nabarro stresses (σ_p) for edge and screw dislocations along various slip planes in Mg-X (X = Y, Ca, Nd, Zn, Al and Sn) alloys are firstly derivate, as well as the calculation of the parameter K (energy factor) based on the first-principles calculation. The effects of solute atoms on the σ_p of various types of dislocations are systematically studied. The difference of the σ_p between the Mg-X alloy and pure Mg, i.e., Δσ_p, is determined, which is strongly influenced by the solute atoms. The negative Δσ_p reflects the promotion of dislocation activation. The relationship between the Δσ_p of different non-basal dislocations and elongation in eight Mg-X alloys is explored. The simultaneous improvement of the activation of the prismatic 〈a〉 and the pyramidal 〈c + a〉 dislocations is discovered, which can be achieved by specific alloying elements. Cooperative activation of the prismatic 〈a〉 and the pyramidal 〈c + a〉 dislocations owing to the reduced Δσ_p is shown to closely correlate with the significant increased plasticity of the Mg alloys. These findings advance a novel perspective on alloy design strategies for Mg alloys with improved plasticity.

Surface properties of crystals are critical in many fields, including electrochemistry and photoelectronics, the efficient prediction of which can expedite the design and optimization of catalysts, batteries, alloys etc. However, we are still far from realizing this vision due to the rarity of surface property-related databases, especially for multicomponent compounds, due to the large sample spaces and limited computing resources. In this work, we present a surface emphasized multi-task crystal graph convolutional neural network (SEM-CGCNN) to predict multiple surface properties simultaneously from crystal structures. The model is evaluated on a dataset of 3526 surface energies and work functions of binary magnesium intermetallics obtained through first-principles calculations, and obvious improvements are observed both in efficiency and accuracy over the original CGCNN model. By transferring the pre-trained model to the datasets of pure metals and other intermetallics, the fine-tuned SEM-CGCNN outperforms learning from scratch and can be further applied to other surface properties and materials systems. This study could be a paradigm for the end-to-end mapping of atomic structures to anisotropic surface properties of crystals, which provides an efficient framework to understand and screen materials with desired surface characteristics.

In this study, we investigated the oxidation of the Mg-11Y-1Al alloy at 500 ℃ in an Ar-20%O₂ environment. Multiscale analysis showed the network-like long-period stacking ordered (LPSO) phase transformed into needle-like LPSO and polygonal Mg₂₄Y₅ phases, leading to the formation of a high-dense network of needle-like oxides at the oxidation front. These oxides grew laterally along the oxide/matrix interfaces, forming a thicker, continuous scale that effectively blocked elemental diffusion. Hence, the preferential oxidation along the needle-like LPSO is believed to accelerate the formation of a thicker and continuous oxide scale, further improving the oxidation resistance of the Mg-11Y-1Al alloy.

Pure Mg boasting a relatively small corrosion rate is a potential biodegradable metal material for implants. However, its degradation behavior in the complex physiological environment is still a lack of understanding. In this work, we investigated the effect of corrosion product film layers on the degradation behavior of pure Mg in physiological environments. Pure Mg shows a faster corrosion rate in simulated body fluid (SBF) compared to NaCl solution. Hydrogen evolution experiments indicate that the degradation rate of pure Mg in SBF decreases rapidly within the first 12 h but stabilizes afterward. The rapid deposition of low-solubility calcium phosphate on the pure Mg in SBF provides protection to the substrate, resulting in a gradual decrease in the degradation rates. Consequently, the corrosion product film of pure Mg formed in SBF exhibits a layered structure, with the upper layer consisting of dense Ca₃(PO₄)₂/Mg₃(PO₄)₂ and the lower layer consisting of Mg(OH)₂/MgO. Electrochemical impedance spectroscopy (EIS) shows that the resistance of the corrosion product film increases over time, indicating gradual strengthening of the corrosion resistance. The 4-week degradation results in the femoral marrow cavity of mice are consistent with the result in SBF in vitro.

The mechanical properties of Mg–Al–Ca alloys are significantly affected by their Laves phases, including the Al₂Ca phase. Laves phases are generally considered to be brittle and have a detrimental effect on the ductility of Mg. Recently, the Al₂Ca phase was shown to undergo plastic deformation in a dilute Mg-Al-Ca alloy to increase the ductility and work hardening of the alloy. In the present study, we investigated the extent to which the deformation of Al₂Ca is driven by dislocations in the Mg matrix by simulating the interactions between the basal edge dislocations and Al₂Ca particles. In particular, the effects of the interparticle spacing, particle orientation, and particle size were considered. Shearing of small particles and dislocation cross-slips near large particles were observed. Both events contribute to strengthening, and accommodate to plasticity. The shear resistance of the dislocation to bypass the particles increased as the particle size increased. The critical resolved shear stress (CRSS) for activating dislocations and stacking faults was easier to reach for small Al₂Ca particles owing to the higher local shear stress, which is consistent with the experimental observations. Overall, this work elucidates the driving force for Al₂Ca particles in Mg–Al–Ca alloys to undergo plastic deformation.

In our previous work, die cast LA42 (Mg–4La–2.5Al–0.3Mn, wt.%) alloy with an excellent combination of thermal-conducting performance and mechanical properties was developed. This study, taking commercial die cast AZ91 (Mg-9Al-1 Zn, wt.%) alloy as a comparison, investigates the microstructure and corrosion behavior of the LA42 alloy in chloride-containing environment. The findings revealed that the microstructure of die cast LA42 alloy displays an Al-depleted α-Mg dendrite and a network shape eutectic phase comprising of eutectic α-Mg and lamellar Al₁₁La₃. The LA42 alloy exhibited slightly inferior corrosion resistance and deeper corrosion pits than the AZ91 alloy, which were related to the interphase attack and the presence of a layer of corrosion products containing more magnesium hydroxide of the LA42 alloy. The corrosion behavior of the LA42 alloy was characterized by an interphase attack on the periphery of Al-depleted α-Mg dendrite adjacent to Al₁₁La₃, which primarily ascribed to the relatively lower potential of the Al-depleted α-Mg phase and the interfacial reactivity between it and the adjacent Al₁₁La₃, whereas the AZ91 alloy showed a trait of preferential corrosion of the interior of α-Mg dendrite for its lowest potential among different phases. This comprehensive research can provide a guidance for future alloy design of Mg-Al-La alloys and their industrial applications.

Magnesium (Mg) alloys have shown great prospects as both structural and biomedical materials, while poor corrosion resistance limits their further application. In this work, to avoid the time-consuming and laborious experiment trial, a high-throughput computational strategy based on first-principles calculations is designed for screening corrosion-resistant binary Mg alloy with intermetallics, from both the thermodynamic and kinetic perspectives. The stable binary Mg intermetallics with low equilibrium potential difference with respect to the Mg matrix are firstly identified. Then, the hydrogen adsorption energies on the surfaces of these Mg intermetallics are calculated, and the corrosion exchange current density is further calculated by a hydrogen evolution reaction (HER) kinetic model. Several intermetallics, e.g. Y₃Mg, Y₂Mg and La₅Mg, are identified to be promising intermetallics which might effectively hinder the cathodic HER. Furthermore, machine learning (ML) models are developed to predict Mg intermetallics with proper hydrogen adsorption energy employing work function (W_f) and weighted first ionization energy (WFIE). The generalization of the ML models is tested on five new binary Mg intermetallics with the average root mean square error (RMSE) of 0.11 eV. This study not only predicts some promising binary Mg intermetallics which may suppress the galvanic corrosion, but also provides a high-throughput screening strategy and ML models for the design of corrosion-resistant alloy, which can be extended to ternary Mg alloys or other alloy systems.