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A cost-effective, high-performance Mg-2.0Zn-1.5Mn alloy was fabricated using closed forging extrusion (CFE). The results reveal that CFE can promote a dynamic recrystallization (DRX) ratio and enhance the residual dislocation density in deformed grains and subgrains. Grain refinement is achieved through multiple DRX mechanisms, particle-stimulated nucleation, and pinning effects. In addition, the basal texture and precipitation behavior are significantly influenced by pre-forging in CFE. Finally, grain refinement and substantial residual dislocations result in a good combination of strength and plasticity, with the ultimate tensile strength of 400 MPa and elongation of 22.1%, respectively. A novel strategy for regulating the bimodal grain structure is proposed to guide the optimization of the mechanical performance of rare-earth free Mg alloys.

Mg–1Mn alloy, extruded at a low temperature in our published protocol, contributed to the intensified basal texture and extremely refined microstructure with spheroidal nanoscale precipitates dispersing throughout the matrix and along the grain boundaries, consequently resulting in the excellent mechanical properties where the alloy exhibited a tensile yield strength of 204.3 MPa and a ductility of 38.8% at room temperature. Therefore, Mg–1Mn alloy was recommended as one of the potential materials for structural applications. In the present investigation, hot deformation behavior through constitutive analysis and extrusion temperature-dependent microstructure, texture and mechanical properties of as-extruded Mg–1Mn alloy were investigated, aiming at revealing how extrusion temperature affected microstructure, texture, and mechanical properties of as-extruded Mg–1Mn alloy. X-ray diffraction patterns demonstrated that phase components of the experimental alloys consisted of the α-Mg matrix and Mn precipitates. Optical microscopy images indicated a significant increase in average grain size of the alloys as the extrusion temperature increasing from 250 °C to 400 °C. Scanning electron microscopy graphics revealed that coarsened particles identified as Mn precipitates by EDS were observed within the matrix when extrusion temperature reached 400 °C. Inverse pole figure maps of the experimental samples subjected to different extrusion temperatures in the present work exhibited the typical basal texture, suggesting that basal slip was activated hardly during the tensile stress applied along the extrusion direction. Consequently, extrusion temperature displayed the significant impact on microstructure, texture, and mechanical properties of as-extruded Mg–1Mn alloy. The alloy extruded at both 250 °C and 300 °C exhibited the strong basal texture and refined microstructure with spheroidal nanoscale precipitates dispersing within the matrix and along the grain boundaries, which contributed to their excellent comprehensive mechanical properties. The alloy extruded at 400 °C possessed the typical basal texture and coarsened microstructure, leading to the extremely poor mechanical properties. Simultaneously, the constitutive model of the Arrhenius equation based on Zener-Hollomon parameters was also established in the present investigation. Therefore, optimizing the extrusion temperature to regulate the microstructure, grain orientation distribution, and morphology of precipitates was considered as one of the effective approaches for achieving the excellent mechanical properties of Mg alloys.

As the lightest metal structural materials, Mg alloys have great application potential in transportation, aerospace, and biomedicine. However, the further application is hindered by their low strength, plasticity, and poor corrosion resistance. The preparation of Mg alloys with ultra-fine grain (UFG) structure is regarded as a good solution to improve their performance, and has been reported by a large number of literatures. The purpose of this paper is to summarize the development of fabrication processes of UFG Mg alloys and the effects of UFG structure on the mechanical properties and corrosion resistance. In essence, this review aims to elucidate the evolution and current state of UFG structure in Mg alloys. Additionally, it seeks to expound upon the strategies for designing and preparing these structures and shed light on the future development trends. The ultimate goal is to advance the utilization of UFG Mg alloys in both structural and functional materials.

Twinning is a significant deformation mode in zirconium (Zr). Here we investigated the primary displacement cascades near the twin boundary (TB) and mechanical properties in Zr using molecular dynamics simulations. The results show that {10 1‾2} and {10 1‾1} TBs can act as an effective sink for point defects to enhance irradiation resistance in Zr. The {10 1‾2} TB exhibits better sink efficiency than {10 1‾1} TB. Hence, it's recommended to employ Zr alloys with more {10 1‾2} deformation twinning microstructure in irradiation conditions. The present work predicts the introduction of TBs may contribute to a decrease in the density of large-sized clusters and clustered fraction. Further, irradiation leads to localized deformation of the two TBs even in one single collision cascade. The tensile loading of the unirradiated and irradiated samples indicates that the stacking faults serve as an important deformation mechanism in two TB models. The results not only present a reference for understanding the TB structure in the displacement cascades of Zr and its alloys but also provide further support for the design of irradiation-resistant nanotwinned metals.

This study investigates the impact of Gd elements on the enhancement of ductility in the Mg–Gd–Zr alloy. The deformation behavior at room temperature of the cast Mg–Gd–Zr alloy and the cast Mg–Zr alloy was examined using the EBSD-assisted slip trace method. The quantitative analysis of the initiation ratio of each slip system in the two alloys revealed that the Mg–Gd–Zr alloy had a higher ratio of non-basal slip systems. The experimental determination of the critical resolved shear stress (CRSS) ratios of non-basal slip to basal slip for both alloys indicated that the Gd elements could reduce this ratio, facilitating the initiation of more non-basal slip systems to accommodate strain. Furthermore, the segregation of Gd elements at grain boundaries was observed to enhance the grain boundary strength of the alloy, which is a significant factor in the enhancement of ductility.

Diffusion couples for the Mg–Ag–Zn system were prepared using hcp-Mg single-phase solid solution alloys and pure magnesium (Mg). Their diffusion behaviour at 675–753K was analysed and the related diffusion coefficients were obtained. Combining these experimental results and the thermodynamic description, the atomic mobility parameters were optimised, and the kinetic database of the Mg–Ag–Zn ternary system was constructed for the first time. According to the thermodynamic and kinetic descriptions, the diffusion coefficients for concentration range of hcp-Mg (silver (Ag): 0–3 at% and zinc (Zn): 0–3 at%) were calculated. Finally, the composition and temperature dependence of the interdiffusion coefficients was further discussed using first-principles calculations and thermodynamic factors.

Grain size is the critical characteristic of ultra-fine grain Magnesium (Mg), which is a concrete representation of the whole heat deformation procedure. In this paper, a design strategy was proposed to quantitatively investigate the composition and process conditions for the preparation of ultrafine grains. Herein, a dataset of Mg–Mn-based wrought alloys was constructed, and the average grain size was set as the design target. Based on this dataset, five machine learning (ML) algorithms, including the k-nearest neighbor (kNN), support vector machine (SVM), decision tree (DT), random forest (RF), and artificial neural network (ANN), were integrated to conduct in-depth analysis and make predictions. Among these models, the computational accuracy of both the DT classifier and ANN predictor is around 90%. The main factors affecting the formation of ultrafine grains were found by ML, and the interrelationships between the features were quantitatively analyzed as well. Then, four suggested routes with conditions were extracted from the tree models for preparing ultrafine grain Mg alloys. And four new Mg alloys were designed through these routes and taken as experimental validation. After testing, the actual grain sizes are close to the predictions, and the accuracy of the experimental verification exceeds 80%. Compared with conventional “trial and error” design methods, the grain design strategy proposed in this paper brings new thought and good prior guidance for developing high-performance commercial Mg alloys.

This work systematically investigates the impact of the dilute Sc addition on microstructures and mechanical properties in Mg alloys. Electron back scattered diffraction, slip traces analysis, transmission electron microscopy, and visco-plastic self-consistent polycrystal constitutive (VPSC) modeling were performed to investigate the deformation mechanisms in the tensile testing, especially the activation of slip. The results showed that as-solid solution samples only consisted of α-Mg phase. After extrusion, all samples exhibited a similar average grain size. With the increment of the Sc content, the ductility of the samples was significantly improved, which failure elongation (FL) of Mg-xSc (x = 0.3, 0.6, 0.9 wt.%) alloys improved from 14.4% to 24.8%. The yield strength of each alloy is similar, about 200 MPa. VPSC results indicated that the difference value of the initial slip resistance (τ0) between prismatic slip and basal slip decreases from 63 MPa to 49 MPa, and the difference value of τ0 between pyramidal slip and basal slip decreases from 72 MPa to 57 MPa. The VPSC and the two-beam diffraction results confirmed that the pyramidal slip and prismatic slip were activated in tensile testing. The quantitative analysis of the slip trace line verified that the volume of non-basal slip reached 49.5% when the Sc content increased to 0.9 wt.%. Therefore, the addition of Sc in solid solution increased the amount of pyramidal and prismatic dislocation activities during the deformation process, which was beneficial to coordinate the c-axis strain, and finally improved ductility of Mg alloy.

The solution behavior of alloying elements is crucial for the design of Mg alloys. The plasticity, strength and corrosion resistance of Mg alloys can be tailored by alloying elements in solid solution in the primary Mg phase. In this work, the interaction and solution behavior of 24 alloying elements in Mg alloys, including 24 binary systems and 88 ternary systems, was studied. Features characterizing the interactions of solute elements in the primary Mg phase, including atomic substitutional sites, volume difference, c/a ratio and formation energy, of these alloys were calculated by first principles. Relations between the interaction features and the alloying elements’ characteristics were constructed based on machine learning methods, in which strong correlations were observed. Additionally, the electronic and atomic origin of the interaction features in solid solution ternary Mg alloys were analyzed. This work provides new insights into the design of high-performance multicomponent Mg alloys, as well as the construction of atomic models for other alloys.

The recrystallization behavior of extruded Mg–Zn–Mn alloys was systematically investigated under different aging treatment prior to extrusion. Electron backscattered diffraction analysis was used to explore the recrystallization mechanism and corresponding effects on the basal texture of alloys during extrusion. The results show that the primary coarse particles can effectively promote recrystallization nucleation. Moreover, the precipitation of nanoscale particles during the aging process play a role in pinning the grain boundaries. Therefore, after peak-aged treatment (16 h), the extruded Mg alloy obtains uniform and fine microstructure, showing good mechanical properties: the tensile yield strength, tensile strength, elongation, compressive yield strength, and tension-compression yield asymmetry were 298 MPa, 363 MPa, 26%, 260 MPa, and 0.87, respectively.

Within the scope of this study, the evolution of microstructures and mechanical properties in as-extruded Mg–Sc alloys were systematically explored with Mn content from 0.3 to 0.9 wt.%. The results showed that a completely recrystallized crystal structure was obtained in Mg-xMn-Sc alloys, and the average grain size decreased from 12.75 to 3.35 μm with the increase of Mn content. In addition, the increment of Mn content reduced the texture intensity from 14.95 to 7.65. Thus, Mg–Sc alloys’ tensile yield and ultimate strength significantly improved. Meanwhile, Mn addition led to the activation of non-basal slip, especially prismatic slip, which significantly enhanced the ductility of alloys. Moreover, the activation of non-basal slip by alloying Mn can be attributed to the reduction of the critical shear stress (CRSS) gap between basal slip and non-basal slip.

The additions of alloying elements can significantly improve the mechanical properties of magnesium (Mg) alloys, mainly due to the fact that their additions change the critical shear stresses (CRSS) for dislocation slips. In this work, experimental and computational methods were used to explore the mechanisms responsible for the roles of Sm element addition in affecting the mechanical properties of Mg. The results showed that the addition of Sm obviously improves the microstructure and mechanical properties. It promotes the formation of twins and beneficially activated the non-basal slip at the initial stage of plastic deformation, resulting in a high ductility. The Visco-Plastic Self-Consistent (VPSC) and the two-beam diffraction results confirmed that the pyramidal slip and prismatic slip were activated during tensile testing. The quantitative analysis of slip traces verified that the volume of non-basal slips reached 35 % after Sm addition. The additions of Sm with solid solution increased the activities of pyramidal dislocation during deformation, which was beneficial to accommodate the c-axis strain, and finally improved the room temperature ductility of Mg. First-principle calculations demonstrate that the solute Sm atoms would reduce the stacking fault energy for basal and prismatic slips.

Ternary magnesium-based alloys with an aluminum content of 0.5 wt.% and a varying manganese content of x = 1, 2, and 3 wt.% (Mg-xMn-0.5Al) were prepared and characterized. The study focused on the effect of Mn addition on the formation of ultrafine grains (UFGs, average grain size