This work presents a method to incorporate the micro Hall-Petch equation into the crystal plasticity finite element (CPFE) framework accounting for the microstructural features to understand the coupling between grain size, texture, and loading direction in magnesium alloys. The effect of grain size and texture is accounted for by modifying the slip resistances of individual basal and prismatic systems based on the micro Hall-Petch equation. The modification based on the micro Hall-Petch equation endows every slip system at each microstructural point with a slip system-level grain size and maximum compatibility factor, which are in turn used to modify the slip resistance. While the slip-system level grain size is a measure of the grain size, the maximum compatibility factor encodes the effect of the grain boundary on the slip system resistance modification and is computed based on the Luster-Morris factor. The model is calibrated using experimental stress-strain curves of Mg-4Al samples with three different grain sizes from which the Hall-Petch coefficients are extracted and compared with Hall-Petch coefficients predicted using original parameters from previous work. The predictability of the model is then evaluated for a Mg-4Al sample with different texture and three grain sizes subjected to loading in different directions. The calibrated parameters are then used for some parametric studies to investigate the variation of Hall-Petch slope for different degrees of simulated spread in basal texture, variation of Hall-Petch slope with loading direction relative to basal poles for a microstructure with strong basal texture, and variation of yield strength with change in grain morphology. The proposed approach to incorporate the micro Hall-Petch equation into the CPFE framework provides a foundation to quantitatively model more complicated scenarios of coupling between grain size, texture and loading direction in the plasticity of Mg alloys.

Magnesium hydride (MgH2) is the most feasible and effective solid-state hydrogen storage material, which has excellent reversibility but initiates decomposing at high temperatures and has slow kinetics performance. Here, zinc titanate (Zn2TiO4) synthesised by the solid-state method was used as an additive to lower the initial temperature for dehydrogenation and enhance the re/dehydrogenation behaviour of MgH2. With the presence of Zn2TiO4, the starting temperature for the dehydrogenation of MgH2 was remarkably lowered to around 290°C–305°C. In addition, within 300 s, the MgH2–Zn2TiO4 sample absorbed 5.0 wt.% of H2 and 2.2–3.6 wt.% H2 was liberated from the composite sample in 30 min, which is faster by 22–36 times than as-milled MgH2. The activation energy of the MgH2 for the dehydrogenation process was also downshifted to 105.5 kJ/mol with the addition of Zn2TiO4 indicating a decrease of 22% than as-milled MgH2. The superior behaviour of MgH2 was due to the formation of MgZn2, MgO and MgTiO3, which are responsible for ameliorating the re/dehydrogenation behaviour of MgH2. These findings provide a new understanding of the hydrogen storage behaviour of the catalysed-MgH2 system.

A computationally efficient two-surface plasticity model is assessed against crystal plasticity. Focus is laid on the mechanical behavior of magnesium alloys in the presence of ductility-limiting defects, such as voids. The two surfaces separately account for slip and twinning such that the constitutive formulation captures the evolving plastic anisotropy and evolving tension-compression asymmetry. For model identification, a procedure is proposed whereby the initial guess is based on a combination of experimental data and computationally intensive polycrystal calculations from the literature. In drawing direct comparisons with crystal plasticity, of which the proposed model constitutes a heuristically derived reduced-order model, the available crystal plasticity simulations are grouped in two datasets. A calibration set contains minimal data for both pristine and porous material subjected to one loading path. Then the two-surface model is assessed against a broader set of crystal plasticity simulations for voided unit cells under various stress states and two loading orientations. The assessment also includes microstructure evolution (rate of growth of porosity and void distortion). The ability of the two-surface model to capture essential features of crystal plasticity is analyzed along with an evaluation of computational cost. The prospects of using the model in guiding the development of physically sound damage models in Mg alloys are put forth in the context of high-throughput simulations.

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.

Cardiovascular stent has been widely applied to treat cardiovascular disease (CVD), which is the major disease contribution to mortality in the world wide. Biodegradable magnesium (Mg) alloys are the encouraging materials in cardiovascular stents benefit from absorbability and biocompatibility. While, the ability of degradation is a double-edged sword for manufacture stent, modifying the surface to decrease the excessive degradation rate and promote the surface endothelialization could expand the prospect of the further application. In this work, the biodegradable Mg-Zn-Y-Nd alloy was modified by MgF2 and dopamine polymer film (PDA) as the corrosion resistance layer and the bonding layer respectively, and then the exosome, a natural nanoparticle contains mRNAs and proteins, was tailored to give the surface better biocompatibility. The electrochemical test and weight loss test reflected the MgF2-PDA/exosome coating increase the corrosion resistance of the Mg-Zn-Y-Nd alloy. The cytocompatibility data indicated the novel MgF2-PDA/exosome coating selectively reduced the tumor necrosis factor (TNF-α) expression and ROS release from macrophage, and promoted the α-SMA expression of smooth muscle cells. In addition, the MgF2-PDA/exosome coating also improved the adhesion, proliferation, CD31 expression and nitric oxide (NO) release of vascular endothelial cells (ECs), all of which contribute to the surface endothelialization. And the mechanism experiments showed the exosome released from the coating uptake by the ECs and assemble around the lysosome and mitochondria, and the released rate of the exosome on the coating is around 5 to7 days, indicating excellent multi-functions of MgF2-PDA/exosome coating in cardiovascular stent.

Magnesium (Mg) composites reinforced with carbon-based nanomaterial (CBN) often exhibit low density, enhanced strength, good conductivity, improved wear resistance, and excellent biocompatibility when compared to current industry Mg alloys. This review aims to critically evaluate recent developments in Mg-CBN composites and is divided into five sections: First, a brief introduction to Mg-CBN composites is provided, followed by a discussion of different fabrication techniques for these composites, including powder metallurgy, casting, friction stir processing, and selective laser melting. A particular focus is on the current processing challenges, including dispersion strategies to create homogeneous Mg-CBN composites. The effect of processing on the quantifying disorder in CBNs and distinguishing different sp2 carbon materials is also highlighted. Then, the effect of CBN on various properties of Mg-CBN composites is thoroughly analyzed, and the strengthening efficiency of CNTs and graphene in the Mg matrix is examined. Finally, the potential applications of Mg-CBN composites in various industries are proposed, followed by a summary and suggestions for future research directions in the field of Mg-CBN composites.

Studies have been conducted on the corrosive behavior of magnesium in aqueous sulfate electrolytes (0.5 mol/L MgSO4; 0.5 mol/L Na2SO4; 0.5 mol/L MgSO4 + 0.5 mol/L Na2SO4).The composition structure and morphology of the surface of the samples were studied using scanning electron microscopy in combination with X-ray spectral microanalysis. The results of the experiments showed the formation of a surface film inhomogeneous in its structure and composition with the main components Mg(OH)2 and MgO. An increase in the exposure time of the electrode in solution led to the formation of microcracks on the main film caused by internal stress because of hydration of magnesium oxide produced during corrosion. The salt composition of the electrolyte determines the morphology and thickness of corrosion films due to differences in the solubility of the products formed during the hydrolysis of magnesium oxide and the kinetics of this process.Applying the methods of scanning electron microscopy X-ray electron analysis gravimetry and voltammetry it has been established that at various stages of magnesium corrosion in different electrolytes the growth rates of corrosion films are determined by the kinetics of magnesium oxide formation its hydration and dissolution followed by crystallization in the form of a brucite phase of loose sediments on the surface.

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Strength-ductility trade-off is a common issue in Mg alloys. This work proposed that a synergistic enhancement of strength and ductility could be achieved through tuning interlayer dwell time (IDT) in the wire and arc additive manufacturing (WAAM) process of Mg alloy. The thermal couples were used to monitor the thermal history during the WAAM process. Additionally, the effect of different IDTs on the microstructure characteristics and resultant mechanical properties of WAAM-processed Mg alloy thin-wall were investigated. The results showed that the stable temperature of the thin-wall component could reach 290 °C at IDT=0s, indicating that the thermal accumulation effect was remarkable. Consequently, unimodal coarse grains with an average size of 39.6 µm were generated, and the resultant room-temperature tensile property was poor. With the IDT extended to 60s, the thermal input and thermal dissipation reached a balance, and the stable temperature was only 170 °C, closing to the initial temperature of the substrate. A refined grain structure with bimodal size distribution was obtained. The remelting zone had fine grains with the size of 15.2 µm, while the arc zone owned coarse grains with the size of 24.5 µm. The alternatively distributed coarse and fine grains lead to the elimination of strength-ductility trade-off. The ultimate tensile strength and elongation of the samples at IDT=60s are increased by 20.6 and 75.0% of those samples at IDT=0s, respectively. The findings will facilitate the development of additive manufacturing processes for advanced Mg alloys.

Hot torsion tests for AZ80 magnesium alloy were carried out in the temperature range of 380 °C-260 °C, with a constant decreasing temperature rate of 10 °C/s in order to weaken the basal texture and refine the grains. The results indicated that the average grain sizes were refined forming gradient structure with increasing specimen radial position from center (12.2–5.4 μm), and that the initial basal texture intensity of the extruded magnesium alloy was weakened from 46.2 to 8.3. Furthermore, the extension twins (ETs) could be disintegrated from the twins forming separated twins with smaller sizes. Interestingly, ETs with the same twin variant intersecting with each other could be coalesced forming grains with similar orientation, while ETs with different twin variants were separated by twins boundaries contributing to grain refinement. Moreover, in addition to the conventional continuous dynamic recrystallized (CDRX) grains with 30˚ orientation rotated around C-axis of the parent grains, CDRXed grains with 30˚ rotation around a-axis and random rotation axis were also discerned. Besides, the CDRX evolution induced twins were also elaborated, exhibiting the complex competition between CDRX and twining. Hot torsion deformation with constant decreasing temperatures rate is an effective way of grain refinement and texture modification.

To understand the interface characteristics between the precipitate β2′ and the Mg matrix, and thus guide the development of new Mg-Zn alloys, we investigated the atomic interface structure, work of adhesion (Wad), and interfacial energy (γ) of Mg(0001)/β2'(MgZn2)(0001) interface, as well as the effect of segregation behavior of the introduced transition metal atoms (3d, 4d and 5d) on interfacial bonding strength. The calculated works of adhesion and interfacial energies dementated that the Zn2-terminated MT+HCP configuration is the most stable structure for all considered models. Take the Zn2- MT+HCP interface as the research object, estimated segregated energies (Eseg) reveal that added transition metal atoms prefer to segregate at Mg-I and Mg-II sites. The predicted Wad and charge density difference results reveal that the segregation of alloying additives employed may all strengthen Mg(0001)/MgZn2(0001) interface, with the enhancement effect of Os, Re, Tc, W, and Ru at the Mg-II site being the most pronounced.

Galvanic corrosion behavior of AZ91D alloy / 45 steel couple in 3.5 wt.% NaCl solution under 0, 0.2 and 0.4 T magnetic field were studied by microstructure observation, immersion test and electrochemical measurement. The mixed potential theory was used to estimate the galvanic current density and the mixed potential of the galvanic corrosion between AZ91D alloy and 45 steel. The results indicated that magnetic field could accelerate the corrosion of AZ91D alloy, and impede the corrosion process of 45 steel. The effect of magnetic field on corrosion sensibility and corrosion rate of these two alloys increased as the intensity rising. The galvanic corrosion rate of the couple was accelerated by magnetic field. With the magnetic field intensity rising, the galvanic corrosion sensibility and corrosion rate of the couple increased. The effects of magnetic field on the galvanic corrosion performance of the couple and the corrosion behavior of AZ91D alloy and 45 steel were due to the appearance of field gradient force and magnetohydrodynamic (MHD) force. The mixed potential theory has a certain accuracy to estimate the Ecouple and icouple values in this work.

The primary cause of the decrease in thermal conductivity of conventional thermal conductive magnesium alloys is electron scattering brought on by solute atoms. However, the impact of phase interface on thermal conductivity of magnesium alloys is usually disregarded. This study has developed a Mg-Si-Zn-Cu alloy with high thermal conductivity that is distinguished by having a very low solute atom content and a significant number of phase interfaces. The thermal conductivity of the Mg-1.38Si-0.5Zn-0.5Cu alloy raises from its untreated value of 133.2 W/(m·K) to 142.2 W/(m·K), which is 91% of the thermal conductivity of pure Mg. This is accomplished by subjecting the alloy to both 0.8wt% Ce modification and T6 heat treatment. The morphology of eutectic Mg2Si phase is changed by Ce modification and heat treatment, and as a result, the scattering of electrons at the Mg2Si/Mg interface is reduced, resulting in increase of the alloy's thermal conductivity.

In this work, a new strategy for achieving ultrahigh strength in the coarse-grained Mg-Gd binary alloy via utilizing recrystallization texture hardening and maximizing precipitation strengthening has been reported. Forging at a much high temperature suppresses dynamic precipitation, enabling the super-saturation of Gd atoms in Mg matrix. This facilitates the formation of fully recrystallized grains with strong texture and induces an exceptionally high precipitation hardening in the following ageing. Therefore, the forged Mg-13Gd sample exhibited extraordinary tensile yield strength (TYS) of ∼430 MPa, in which ageing-induced TYS increment exceeds ∼210 MPa, as the highest record so far in precipitation-hardened Mg communities. These results provide important theoretical guidance for fabricating the large section and high-strength Mg components for industrial applications.

Due to its excellent biocompatibility and biodegradability, Mg and its alloys are considered to be promising materials for manufacturing of vascular sent. However, the manufacture of high-precision and high-performance Mg alloys minitubes is still a worldwide problem with a long manufacturing processing caused by the poor workability of Mg alloys. To solve this problem, the cyclic extrusion compression (CEC) was used to pretreat the billet by improving the workability of Mg alloys, finally shortening the manufacturing process. After CEC treatment, the size of grains and second phase particles of Mg alloys were dramatically refined to 3.2 µm and 0.3 µm, respectively. Only after three passes of cold drawing, the wall thickness of minitube was reduced from 0.200 mm to 0.135 mm and a length was more than 1000 mm. The error of wall thickness was measured to be less than 0.01 mm, implying a high dimensional accuracy. The yield strength (YS), ultimate tensile strength (UTS) and elongation of finished minitube were 220±10 MPa, 290±10 MPa and 22.0 ± 0.5%, respectively. In addition, annealing can improve mechanical property and corrosion resistance of minitubes by improving the homogeneity of the microstructure and enhancing the density of basal texture.

Magnesium (Mg) alloys have been widely used in automobile, aviation, computer, and other fields due to their lightweight, high specific strength and stiffness, low pollution, and good electromagnetic shielding performance. However, the chemical stability of Mg alloys is poor, especially in the corrosive medium environment with high stress corrosion sensitivity, which causes sudden damage to structural components and restricts their application field. In recent years, owing to the increasing failure rate of engineering structures caused by stress corrosion of Mg alloys, it has become necessary to understand and pay more attention to the stress corrosion cracking (SCC) behavior of Mg alloys. In this paper, the SCC mechanisms and test methods of Mg alloys have been summarized. The recent research progress on SCC of Mg alloys has been reviewed from the aspects of alloying, preparation process, surface modification, corrosive medium, and strain rate. More importantly, future research trends in the field of SCC of Mg alloys have also been proposed.

The relatively insufficient knowledge of the deformation behavior has limited the wide application of the lightest structure material-Mg alloys. Among others, bending behavior is of great importance because it is unavoidably involved in various forming processes, such as folding, stamping, etc. The hexagonal close-packed structure makes it even a strong texture-dependent behavior and even hard to capture and predict. In this regard, the bending behaviors are investigated in terms of both experiments and simulations in the current work. Bending samples with longitudinal directions inclined from the transverse direction by different angles have been prepared from an extruded AZ31 plate, respectively. The moment-curvature curves and strain distribution have been recorded in the four-point bending tests assisted with an in-situ digital image correlation (DIC) system. A crystal-plasticity-based bending-specific approach named EVPSC-BEND was applied to bridge the mechanical response to the microstructure evolution and underlying deformation mechanisms. The flow stress, texture, twin volume fraction, stress distribution, and strain distribution evolve differently from sample to sample, manifesting strong texture-dependent bending behaviors. The underlying mechanisms associated with this texture dependency, especially the occurrence of both twinning and detwinning during the monotonic bending, are carefully discussed. Besides, the simulation has been conducted to reveal the moment-inclination angle relation of the investigated AZ31 extruded plate in terms of the polar coordinate, which intuitively shows the texture-dependent behaviors. Specifically, the samples with longitudinal directions parallel to the extruded direction bear the biggest initial yielding moment.

A bimodal-structured Mg–15Gd binary alloy with 45% volume fraction of elongated grains and 55% of dynamically recrystallized (DRXed) grains is fabricated by the extrusion process. The precipitating behavior correlating with the evolution of mechanical properties is systematically characterized during the subsequent aging treatment at 200 °C. The extruded alloy presents an outstanding strength with tensile yield strength of 466 MPa and ultimate tensile strength of 500 MPa at peak aging condition, while the elongation drops from 9.2% in extrusion state to 3.1%. It is found there obviously exist a rapidly decreasing range of ductility at the early stage of aging. Just during this time, the nano precipitates form preferentially at lamellar dislocation boundaries (LDBs) within the elongated grains, but there is no dense and uniform precipitation in the matrix. The results suggest that the low elongation in the aged Mg–15Gd alloy is mainly attributed to the nano precipitates prior formed at the LDBs with a high density in the elongated grains. The related mechanism has been clarified.

At present, there are few studies on the phase transition during the thermocompression plastic deformation of magnesium alloy. In this study, the evolution model of thermal compression plastic of AZ31 magnesium alloy was constructed by molecular dynamics, and the phase transition relationship between HCP and FCC at different thermal compression rates was studied. By combining GLEEBLE thermal compression experiment with transmission electron microscopy experiment, high-resolution transmission electron microscopy images were taken to analyze the transition rules between HCP and FCC during plastic deformation at different thermal compression rates, and the accuracy of molecular dynamics analysis was verified. It is found that the slip of Shockley's incomplete dislocation produces obvious HCP →FCC phase transition at low strain rate and base plane dislocation at high strain rate, which makes the amorphous phase transition of HCP→OTHER more obvious, which provides theoretical guidance for the formulation of forming mechanism and preparation process of magnesium alloy.