Search

Introducing coherent twin boundaries is an effective way to develop submicron/nano-sized grains with improved thermal stability in polycrystals, which exhibit enhanced mechanical properties of metals, such as high strength, high hardness and high fracture toughness. However, crystalline defects, such as dislocations and disclinations, usually arise at twin boundary junctions, which lead to local stress concentration and property degradation. Here we show that a large number of high-index coherent twin boundaries (e.g., Σ11 and Σ19a) can be produced through a well-controlled deformation twinning process. By using metastable β-Ti alloys as an example and analyzing the broken symmetry associated with deformation twinning, we demonstrate that the abnormal high-index twins result from intercorrelated twinning pathways and twin-twin reactions. The formation mechanism of self-organized multi-twin structures has been analyzed systematically through phase field modeling and simulations. It has been found that, under well designed thermo-mechanical condition, regularly distributed high-index twin boundaries and geometrically-compatible twin boundary junctions (i.e., dislocation/disclination-free) can be produced. The stress/strain condition required to obtain self-organized twins has been quantitatively determined, which provides a theoretical guideline for the development of self-organized submicron/nano-twin metals for unprecedented properties.

Conventional horizontal twin-roll casting (TRC) with steel rollers generally possesses slow casting speed. In this study, the inclined TRC method with Cu rollers was proposed, which significantly increases the casting efficiency. A three-dimensional model of the inclined TRC was established, which revealed the temperature field, solid fraction, velocity distribution, and TRC microstructure of the AA6005 aluminum (Al) alloys by the finite element simulation. We considered the various effects of the pouring temperature, roll gap, and rolling speed on the outlet temperature of the inclined cast rolling zone, and determined the appropriate range of processing parameters. The casting speed of the inclined TRC process could reach ∼5.8–7.9 m/min when the roll gap was 2 and 3 mm. Due to the different contact areas between the melt and two rollers, the temperature field and the shape of the liquid hole were asymmetric, and the isotherm and solidification end point (Kiss point) shifted to the direction of the upper roller at the steady inclined TRC state. The columnar/equiaxed grain structure and the upper shift of central segregation in the inclined TRC sheets were successfully simulated by the finite element method, which was in good agreement with the experiments. Moreover, the inclined TRC method with Cu rollers has high cooling intensity and the potential to eliminate central segregation. The results of this study can effectively reduce the trial-and-error effort, and provide a new insight into the development of the TRC Al alloys.

Mg–Al series sheets usually exhibit an apparent mechanical anisotropy induced by strong basal texture. In this study, a near-isotropic Mg–4.5Al–1.5Sn–0.5Ca–0.2Mn (ATXM5210) alloy was developed via 0.05 wt.% Sr micro-alloying combined with rotated rolling, displaying an ultra-low difference in yield strength (∼5 MPa), ultimate tensile strength (∼2 MPa) and elongation (∼1 %) between the rolling direction (RD) and transverse direction (TD), in contrast to a strong anisotropy of Sr-free alloy. We comparatively investigated the effect of trace Ce, Sm and Sr addition on the microstructure, texture evolution and mechanical properties of rolled ATXM5210 alloy. Specially, Sr-containing alloy possesses a more uniform distribution of finer CaMgSn particles after rolling, whereas coarse particles and particle bands are still distinctive in Sr-free alloys. Furthermore, the addition of Sr contributes to form broader-distributed texture towards both RD and TD with reduced peak intensity (∼10.8), leading to an apparently reduced mechanical anisotropy. The quite low mechanical anisotropy and balanced combination of yield strength (∼220 MPa) and ductility (∼21 %) make the present ATXM5210-0.05Sr alloy suitable for producing intermediate or final products and competitive for various engineering applications.

Twinning-mediated plasticity has great potential for enhancing the strength and plasticity of Mg alloys, which is limited due to the lack of twin types. Here, we report a novel multistage twinning mode, i.e. the dominant twinning mode changes from single [Formula: see text] twins to the co-existence of [Formula: see text] and [Formula: see text] twins, in a deformed Mg-Al-Gd alloy. Introducing novel multistage twinning mode to accommodate strains appreciably along c-axes, combined with the interactions of high-density dislocations and dense twin boundaries, guarantees the high strain hardening of Mg alloys. These findings provide new insights into deformation mechanisms and mechanical properties of Mg-alloys.

Featuring low density and high specific strength, magnesium (Mg) alloys have attracted wide interests in the fields of portable devices and automotive industry. However, the active chemical and electrochemical properties make them susceptible to corrosion in humid, seawater, soil, and chemical medium. Various strategies have revealed certain merits of protecting Mg alloys. Therein, engineering self-repairing coatings is considered as an effective strategy, because they can enable the timely repair for damaged areas, which brings about long-term protection for Mg alloys. In this review, self-repairing coatings on Mg alloys are summarized from two aspects, namely shape restoring coatings and function restoring coatings. Shape restoring coatings benefit for swelling, shrinking, or reassociating reversible chemical bonds to return to the original state and morphology when coatings broken; function self-repairing coatings depend on the release of inhibitors to generate new passive layers on the damaged areas. With the advancement of coating research and to fulfill the demanding requirements of applications, it is an inevitable trend to develop coatings that can integrate multiple functions (such as stimulus response, self-repairing, corrosion warning, and so on). As a novel carrier and barrier, porous solids, especially covalent organic frameworks (COFs), have been respected as the future development of self-repairing coatings on Mg alloys, due to their unique, diverse structures and adjustable functions.

Objective: Half of the patients with acute large artery occlusion (LAO) have poor outcomes after endovascular treatment (EVT). Early complications such as cerebral edema and symptomatic intracranial hemorrhage (sICH) can lead to early neurological deterioration (END), which correlates with hemodynamics. This study aimed to identify the hemodynamic predictors of END and outcomes in LAO patients after EVT. Methods: A total of 76 patients with anterior circulation LAO who underwent EVT and received transcranial Doppler (TCD) monitoring were included. Bilateral middle cerebral artery (MCA) blood flow velocities (BFVs) were measured repeatedly within 1 week. Mean flow velocities (MFV) and MFV index (ipsilateral MFV/contralateral MFV) were calculated. The primary outcome was the incidence of END within 72 h. The secondary outcome was the functional outcome at 90 days—a good outcome was defined as a modified Rankin scale (mRS) score of 0–2, while a poor outcome was defined as an mRS score of 3–6. Results: A total of 13 patients (17.1 %) experienced END within 72 h, including 5 (38.5 %) with cerebral edema, 5 (38.5 %) with sICH, and 3 (23.0 %) with infarct progression. Multivariable logistic regression analysis showed that a higher 24 h MFV index was independently associated with END (aOR 10.5; 95 % CI 2.28–48.30, p = 0.003) and a poor 90-day outcome (aOR 5.10; 95 % CI 1.38–18.78, p = 0.014). The area under the receiver operating characteristic (ROC) curve (AUC) of the 24 h MFV index for predicting END was 0.807 (95 % CI 0.700–0.915, p = 0.0005), the sensitivity was 84.6 %, and the specificity was 66.7 %. At the 1-week TCD follow-up, patients who had poor 90-day outcomes showed significantly higher 1-week iMFV [73.5 (58.4–99.0) vs. 57.7 (45.3–76.3), p = 0.004] and MFV index [1.24 (0.98–1.57) vs.1.0 (0.87–1.15) p = 0.007]. A persistent high MFV index (PHMI) was independently associated with a poor outcome (aOR 7.77, 95 % CI 1.81–33.3, p = 0.006). Conclusion: TCD monitoring within 24 h after EVT in LAO patients can help predict END, while dynamic follow-up within 1 week is valuable in predicting clinical outcomes.

Tailoring recrystallization via particle-stimulated nucleation (PSN) and pinning effects from secondary phase particles effectively weakens textures, which is still challenging for low-alloyed rare earth-free Mg alloys. Herein, the texture of a dilute cold-rolled Mg-2.2Al-0.33Ca (wt.%) alloy is found to reduce with the appearance of transverse direction (TD) texture components during static recrystallization. The texture transition is mainly attributed to the preferential growth of TD-oriented recrystallized grains, resulting from the preferential segregation of Al and Ca atoms on basal-oriented grain boundaries with low misorientation angles. The findings provide an in-depth understanding of texture modification in Mg alloys.

ABSTRACTAchieving high strength-ductility synergy in hard-to-deform high-alloyed Mg-Gd-Y-Zn-Zr alloys by rolling remains a great challenge. In this work, a Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr (wt.%) alloy sheet possessing a high yield strength (YS) of ∼385 MPa, ultimate tensile strength (UTS) of ∼420 MPa and elongation of ∼19% was achieved via a single-pass hard-plate rolling (HPR) process. The high YS is mainly from amounts of submicron FGs and strong interactions between densely distributed γ′ precipitates and pyramidal dislocations in CGs. The activation of multiple slip systems, HDI-hardening effect, and crack suppression effect from γ′ particles, endow the excellent ductility.

Twin boundaries (TBs) are effective sinks for solutes to segregate, as they may drive the structural transformation and therefore tailor the properties of magnesium alloys. In this study, a systematic investigation on the TB segregation energy (Eseg) has been performed for the {101¯2} and {101¯1} TBs by first-principles calculations. The segregation of 19 solute atoms (X: Be, Si, Ge, Zn, Ga, Al, Ag, Sb, Ti, Cd, Sn, Li, Bi, Zr, In, Pb, Na, Ca, and Sr) has been considered at the TBs. The solute atoms smaller than Pb are prone to occupying the compression sites of TBs (exception: Ti and Zr for the {101¯1} twin), while the ones larger than Pb prefer to locate at the extension sites. Further inspections suggest that the segregation of solute atoms into preferable sites can be attributed to the combined effect of bond strengthening and alleviated lattice distortion in the vicinity of TBs. For both of the TBs, the Eseg decreases approximately linearly with an increase in the size deviations (equilibrium volume and atomic radius) between Mg and solute atoms, implying the increased propensity for segregation and the enhanced stability of twins. Considering the segregation potency and solubility, the strengthening effects of the 19 solute atoms on TBs are evaluated. Our calculated results may provide guidance for future design of novel Mg alloys based on TB strengthening.

Developing Mg alloys with high strength-ductility synergy presents a major challenge. In this work, a novel Mg-6Zn-0.2Ca alloy prepared via rotated hard-plate rolling (RHPR) exhibits a simultaneous high yield strength (YS) of ∼268 MPa and ductility of ∼22%. The RHPRed alloy features a fine-grained structure containing high-density low angle boundaries (LAGBs) and densely distributed nano-coherent precipitates, contributing to a remarkable improvement of YS (∼82 MPa) in comparison to the conventional rolling counterpart, while homogenizing tensile deformation. In the RHPRed alloy, the presence of ellipse-shape texture and grain-boundary disclinations adjacent to LAGBs promotes the activity of pyramidal and slip that governs the high ductility. The current work demonstrates the essential role played by high-density LAGBs and nano-coherent precipitates to the high strength-ductility synergy, which may provide insights into microstructural control strategy towards superior performance of Mg-Zn-Ca alloys.

By introducing heterogeneous lamella-structure, we obtained a superior strength-ductility synergy in Mg-alloy associated with excellent strain-hardening ability, i.e. yield strength of ∼251 MPa, tensile strength of ∼393 MPa and elongation of ∼23%. By using advanced characterization techniques, we showed that strengthening was mainly caused by the non-uniform distribution of hetero-deformation induced (HDI) stress associated with grain-boundary disclinations, which are mediated by heterogeneous multi-grain interactions. Induced by grain-boundary disclinations and intergranular slip transfers, a variety of abnormal deformation modes have been activated，which contributed significantly to enhanced ductility. This work suggests a new avenue to evade strength-ductility trade-off dilemma in Mg-alloys.

Due to the significant differences in the formation temperature and crystal structure between the primary α-Mg and eutectic β-Mg17Al12, it is a great challenge to achieve simultaneous refinement of the primary and eutectic phases in Mg-Al based alloys via heterogeneous nucleation. Surprisingly, we found that the α-Mg and β-Mg17Al12 in the AZ80 alloy can be simultaneously refined after 0.2 wt.% Sm addition, with the grain size decreasing from ∼217 ± 15 µm to ∼170 ± 10 µm and the β-Mg17Al12 morphology changing from a typical continuous network to a nod-like or spherical structure. The simultaneous refinement mechanism is investigated through solidification simulation, transmission electron microscopy (TEM), and differential thermal analysis (DTA). In the AZ80-0.2Sm alloy, many Al8Mn4Sm particles can be observed near the center of the α-Mg grains or inside the β-Mg17Al12. Crystallographic calculations further reveal that the Al8Mn4Sm has good crystallographic matching with both the α-Mg and β-Mg17Al12, so it possesses the potency to serve as heterogeneous nucleation sites for both phases. The promoted heterogeneous nucleation on the Al8Mn4Sm decreases the undercooling required by the nucleation of the primary and eutectic phases, which enhances the heterogeneous nucleation rate, thus causing the simultaneous refinement of the α-Mg and β-Mg17Al12. The orientation relationships between the Al8Mn4Sm and Mg/Mg17Al12 are identified, which are [1¯21¯0]Mg//[010]Al8Mn4Sm,(101¯0)Mg//(301)Al8Mn4Sm and [1¯12]Mg17Al12//[010]Al8Mn4Sm,(110)Mg17Al12//(301)Al8Mn4Sm, respectively. Furthermore, the refinement of the β-Mg17Al12 accelerates its dissolution during the solution treatment, which is beneficial for cost saving in industrial applications. Other Al8Mn4RE compounds such as Al8Mn4Y might have the same positive effect on the simultaneous refinement due to the similar physicochemical properties of rare earth elements. This work not only proves the possibility of simultaneously refining the primary and eutectic phases in Mg-Al based alloys via heterogeneous nucleation, but also provides new insights into the development of refiners for cast Mg alloys.

High-temperature solid-solution is indispensable for bake-hardenable dilute Mg alloys, which generally induces grain coarsening. Herein, we report extraordinary thermal stability in a bake-hardenable dilute Mg-1.61Zn-0.57Mn-0.54Ca-0.46Al (wt. %, ZMXA2110) alloy, maintaining fine-grained structure at 450 °C. The thermal stability is stemmed from the Zener pinning effect of dense fine (∼15.0 nm) core–shell β-Mn particles and co-segregation of Zn and Ca at grain boundaries. The fine-grained (∼3.2 μm) dilute alloy exhibits high room-temperature formability in solid-solution condition with an Index Erichsen value of ∼6.0 mm, and impressive yield strength of ∼293 MPa with an evident increment of ∼60 MPa by bake-hardening treatment.

Due to the dynamic evolution of precipitates during thermomechanical processing, the intricate effects of second-phase particles on recrystallization behavior are still far from being clear. In this work, the relevance between static recrystallization and pre-aging precipitates in AZ61 (Mg–6Al–1Zn) alloy was systematically investigated. Our results reveal that the presence of pre-aging precipitates increases stored deformation energy by facilitating the generation of dislocations, thus accelerating the recrystallization rate during the initial recrystallization stage. Besides, these uniform distributed dislocations could act as heterogeneous nucleation sites and promote precipitation of fine dispersoids during the subsequent annealing stage. These dispersoids hinder the movement of dislocations and grain boundaries, leading to the increase of Zener pinning pressure. Therefore, the effect of pre-aging particles on recrystallization kinetics gradually transforms from acceleration to retardation as the annealing time prolongs. This work demonstrates that manipulating the features of precipitates through pre-aging treatment is an applicable strategy to control the static recrystallization behavior of Mg alloys.

In this study, the effect of minor Ce addition (0, 0.1, and, 0.3 wt.%) on the microstructure evolution and mechanical properties of rolled Mg–0.6Al–0.5Mn–0.2Ca (AMX100) alloy sheets is systematically investigated under different annealing processes. With 0.1 wt.% Ce addition, partial Al8Mn5 phases turn into Al8Mn4Ce. With 0.3 wt.% Ce addition, the number of the Al8Mn4Ce further increases and the Al–Ce phases are observed. The single-stage annealed alloys exhibit similar uniform fine-grained structures (∼6 μm) regardless of the Ce content, while the grain sizes of the two-stage annealed alloys increase obviously (∼10.9–11.9 μm). Especially, the abnormal grain growth occurs in the two-stage annealed AMX100-0.3Ce alloy. After the aging treatment, the yield strength (YS) of the two-stage annealed alloys is increased by ∼25–45 MPa, which is greatly higher than that of the single-stage annealed alloys (∼1–8 MPa). Note that the two-stage annealed AMX100–0.1Ce alloy displays a significant age-hardening response with the ultimate tensile strength (UTS) of ∼272 MPa and the elongation to failure (EF) of ∼14%, which is attributed to the formation of Al and Ca enriched Guinier-Preston (G.P.) zones. This work sheds light on the design and fabrication of low-cost dilute magnesium alloys with admirable age-hardening ability.

Nowadays, magnesium (Mg) alloys are promising lightweight structural materials, especially in transportation and aerospace fields, due to their inherent low density and high specific strength. Most of the high-strength Mg alloys exhibit poor formability and ductility at room temperature, which limit their wide applications. However, by proper alloying design and/or delicate microstructural control, some newly developed Mg alloys, including rare-earth (RE) and RE-free ones, show enhanced ductility without significant loss of strength. To identify the critical reasons, recent researches on ductile Mg alloys have been reviewed from the aspects of alloying design strategies and microstructural control via advanced processing technologies. Moreover, some outlooks on enhanced ductility of Mg alloys are suggested, e.g. enhancing the beneficial effect of solute atoms, introducing second phase particles, tailoring bimodal-grained structures, introducing pre-twinning structures, etc. The current research progresses in alloying design and/or novel microstructural control have shed some lights on designing and producing Mg alloys with enhanced ductility.

Fe-containing phases had a critical influence on the mechanical properties especially the ductility of Al–Mg–Si alloys. In the present study, the Fe-containing phases in Al-1.2Mg-0.7Si-0.1Fe (wt.%, AA6061) alloys had been regulated by the combination of sub-rapid solidification (SRS) and alloying with 0.12 wt.% Cr. Consequently, the coarse needle/platelet β-Al5FeSi phases (average length: ∼27 μm) were regulated as polyhedral α-AlCrFeSi phases with smaller size (∼2 μm) and uniform distribution. Based on the thermodynamic calculation of solidification paths, this study developed a possible mechanism of the Fe-containing phase transformation. Specifically, alloying with Cr accelerated the formation of fivefold symmetry icosahedral quasicrystal θ-Al13(Fe, Cr)4 phases (Al13M4 phases), which then combined with Si atoms in the surrounding melt and favored the formation of polyhedral α-AlCrFeSi phases. Tensile properties of artificial aged alloys were significantly improved by the combination of SRS and alloying with 0.12 wt.% Cr. The yield and ultimate strength increased from ∼254 to ∼293 MPa and ∼288–∼335 MPa, respectively, and the elongation to failure increased from ∼10% to ∼21%. This study may provide guidelines to produce high-ductility Al–Mg–Si alloys by optimizing the Fe-containing phases.

Achieving appreciable strain-aging hardening coupling with fine-grain strengthening remains a critical challenge in dilute Mg alloys, as high-temperature solid-solution, utilized to impart high-level solutes for strain-aging, inevitably causes grain coarsening and great strength loss. Herein, we report a rapid dislocation-mediated solute repartitioning behavior upon aging in a low-temperature annealed Mg–1.0Zn–0.45Ca–0.33Sn–0.2Mn (wt.%) alloy. Thereby, appreciable strain-aging hardening (YS increment of ∼30 MPa) coupling with fine-grain (grain size of ∼2.5 µm) strengthening accounts for a high yield strength (∼297 MPa) and ductility (∼20%). It suggests a feasible avenue to develop strong dilute Mg alloys by combining strain-aging hardening and fine-grain strengthening.

Regulating the morphology and composition of Fe-containing phases can significantly improve the mechanical properties of Al–Mg–Si alloys. Here, we successfully prepared the high-performance AA6061 alloys by the route of sub-rapid solidification (SRS) based on twin-roll casting (TRC). Excellent tensile strength (∼372 MPa) and elongation (∼19%) were achieved in the peak-aged TRC sample, which increased simultaneously compared with the counterpart (∼351 MPa and ∼14%) fabricated via ingot casting (IC). It was found that the strength-ductility synergy of the TRC sample was caused by the high cooling rate, wherein the SRS can refine the microstructure significantly and promote the reaction from the AlFeSi to the AlFeMgSi (Mg:Fe:Si = 1:1.5:2.5) phase. The centerline segregation in the TRC strip could be well mitigated during solution treatment because the reduced size and Mg-incorporation accelerated the redissolution of AlFeMgSi phases. The alleviative segregation greatly promoted supersaturated solution, and thus contributing to the synergy of strength and ductility. Meanwhile, the Si-rich AlFeMgSi phase could decompose into the Fe-rich α-AlFeSi (Fe:Si > 1) during solution treatment, which expanded the solid solubility of Si and Mg. Therefore, an enhanced aging hardening response was obtained in the peak-aged TRC sample, showing the high number density and volume fraction of β” phase. The results would provide guidelines for developing high-performance Al–Mg–Si alloys based on the SRS during TRC.

Grain boundary strengthening is an effective strategy for increasing mechanical properties of Mg alloys. However, this method offers limited strengthening in bimodal grain-structured Mg alloys due to the difficultly in increasing the volume fraction of fine grains while keeping a small grain size. Herein, we show that the volume fraction of fine grains (FGs, ∼2.5 µm) in the bimodal grain structure can be tailored from ∼30 vol.% in Mg-9Al-1 Zn (AZ91) to ∼52 vol.% in AZ91–1Y (wt.%) processed by hard plate rolling (HPR). Moreover, a superior combination of a high ultimate tensile strength (∼405 MPa) and decent uniform elongation (∼9%) is achieved in present AZ91–1Y alloy. It reveals that a desired bimodal grain structure can be tailored by the co-regulating effect from coarse Al2Y particles resulting in inhomogeneous recrystallization, and dispersed submicron Mg17Al12 particles depressing the growth of recrystallized grains. The findings offer a valuable insight in tailoring bimodal grain-structured Mg alloys for optimized strength and ductility.

Twin-roll casting (TRC) of Mg alloys with high Al content has unique advantages and broad development prospects. However, the severe segregation of high-alloyed Mg caused by TRC technology is difficult to solve at present, which restricts its practical application. In this work, the homogenization of coarse segregated phases in a twin-roll cast Mg–8Al–2Sn–1Zn (ATZ821) alloy was successfully achieved by a method combining solid-solution heat treatment and controlled rolling, which is suitable for industrial-scale production. In addition, the evolution of the microstructure was studied in detail. It was found that phases dynamically precipitated and dissolved repeatedly during the hot rolling process, and the evolution of entire second phases can be classified into three stages, i.e., the net dissolution, balancing and net precipitation stages. During the process, the large-size chain-like eutectic phases evolved into a fine and nearly spherical (∼0.4 µm) morphology that was uniformly dispersed in the Mg-matrix due to the thermodynamic coupling and the Ostwald ripening effect. Moreover, a fine grain microstructure (∼4 µm) was obtained. The formidable segregation problem of twin-roll cast Mg alloys with high Al content was solved, which is an important finding for the industrial application of high-alloyed twin-roll cast sheets.

Abstract The goal of this study was to improve the accuracy of model forecasting, such that forecasters could use model products to make more efficient daily weather predictions. Historical data of the 12 hr following a given time for various meteorological factors from the control forecasts of the European Centre for Medium‐Range Weather Forecasting (ECMWF) between 20 ° and 40 ° N latitude and 110 °–130 ° E longitude were used to verify the performance of the proposed method. Eight major meteorological factors were selected via correlation analysis between control forecast meteorological factors and real‐time rainfall. The samples were divided into four types using the K‐means clustered method. Each type was respectively modelled by long short‐term memory (LSTM) in order to correct rainfall forecasts for eastern China. The eight major meteorological factors were used as the model input, and the differences between real‐time rainfall data and model‐forecast rainfall were used as the model output. The corrected results revealed that the root mean square error decreased by 0.65, and the threat scores of light rainfall and rainstorms were improved.

The high-temperature superplastic deformation behavior of rolled Mg-8Al-2Sn (AT82) and Mg-8Al-1Sn-1Zn (ATZ811) alloys were investigated in this study. During tensile deformation at 573 K, no obvious grain growth occurred in both alloys, because of the high-volume fraction of second phases located at grain boundaries. Meanwhile, texture weakening was observed, suggesting that grain boundary sliding (GBS) is the dominant superplastic deformation mechanism, which agreed well with the strain rate sensitivity (m) and the activation energy (Q) calculations. The microstructural evolution during tensile deformation manifested that there were more and larger cavities in AT82 than ATZ811 during high-temperature tensile deformation. Therefore, superior superplasticity was found in the ATZ811 alloy that presented a tensile elongation of ~510% under a strain rate of 10−3 s−1 at 573 K, in contrast to the relatively inferior elongation of ~380% for the AT82 alloy. Meanwhile, good tensile properties at ambient temperature were also obtained in ATZ811 alloy, showing the ultimate tensile strength (UTS) of ~355 MPa, yield strength (YS) of ~250 MPa and elongation of ~18%. Excellent mechanical performance at both ambient and elevated temperatures can be realized by using economical elements and conventional rolling process, which is desirable for the industrial application of Mg alloy sheets.

The microstructure, mechanical properties and corrosion behavior of hot⁻rolled Mg⁻xSn⁻1Zn⁻0.5Ca (x = 1, 3 and 5 wt.%) alloys were investigated for possible application as biodegradable implants. The hot⁻rolled Mg⁻xSn⁻1Zn⁻0.5Ca alloys consisted of α-Mg matrix and Mg2Sn phase. The number of the Mg2Sn particles significantly increased and the grains were gradually refined (14.2 ± 1.5, ~10.7 ± 0.7 and ~6.6 ± 1.1 μm), while the recrystallized fraction significantly decreased with the increase in the Sn content, the Mg⁻1Sn⁻1Zn⁻0.5Ca alloy was almost completely recrystallized. Ultimate tensile strength (UTS) and tensile yield strength (TYS) increased slightly, reaching maximum values of 247 MPa and 116 MPa, respectively, for the Mg⁻5Sn⁻1Zn⁻0.5Ca alloy, and the elongation decreased with the increase in the Sn content; the Mg⁻1Sn⁻1Zn⁻0.5Ca alloy showed the highest elongation (15.3%). In addition, immersion tests and electrochemical measurements in Hank’s solution revealed that the corrosion rates of Mg⁻xSn⁻1Zn⁻0.5Ca alloys increased with the increase in the Sn content. A model of the corrosion behavior was discussed for hot⁻rolled Mg⁻xSn⁻1Zn⁻0.5Ca alloys in Hank’s solution. Among the Mg⁻xSn⁻1Zn⁻0.5Ca (x = 1, 3 and 5 wt.%) alloys, Mg⁻1Sn⁻1Zn⁻0.5Ca alloy exhibits optimal corrosion resistance and appropriate mechanical properties.

A high extrusion ratio of 166:1 was applied to commercial AZ61 alloy in one step with an extrusion speed of 2.1 m·min−1. The effects of DA (direct aging) treatment on the microstructure and tensile properties of extruded alloy were investigated. The extruded alloy exhibits fine DRXed grains and the average grain size is ~11 μm. After DA treatment at 170 °C, the tensile strength and 0.2% offset yield strength is enhanced from 314 to 336 MPa and from 169 to 191 MPa respectively, sacrificing elongation from 26.5% to 23.3%. The grain size and texture distribution of extruded AZ61 scarcely evolve during the post aging treatment. However, the enhanced strength in peak-aged alloy is mainly caused by the high-density elliptical Mg17Al12 precipitates distributing uniformly along the grain boundaries or within the grains, by precipitation and dispersion hardening. Furthermore, the nano-sized precipitates effectively inhibit grains from coarsening by triggering pinning effects along the grain boundaries at elevated temperature. As a result, the peak-aged alloy exhibits a better superplasticity of 306.5% compared with that of 231.8% of extruded sample. This work provides a practical one-step method for mass-producing Mg alloy sheets with excellent tensile strength and ductility compared with those fabricated by conventional extrusion methods.

Nano-SiC particulates (n-SiCp) reinforced Mg-8Al-1Sn (AT81) composites with different pre-oxidation parameters were fabricated by powder metallurgy (P/M) process combined with hot extrusion. The effects of pre-oxidization treatment of n-SiCp on the microstructure and tensile properties of 0.5 vol % n-SiCp/AT81 composites were investigated accordingly. The distribution of n-SiCp with different pre-oxidation parameters was homogeneous in the composites. Moreover, it was found that a thin MgAl2O4 layer formed at the interface when the n-SiCp were pre-oxidized at 1073 K for 2 h, while the MgAl2O4 layer became much thicker with pre-oxidization temperature increasing to 1273 K for 2 h. After an appropriate pre-oxidization treatment of n-SiCp at 1073 K for 2 h, the as-extruded 0.5 vol % n-SiCp/AT81 composites exhibited an enhanced strength. It was found that the yield strength (YS) and ultimate tensile strength (UTS) increased from 168 MPa and 311 MPa to 255 MPa and 393 MPa compared with the as-extruded AT81 alloy, reflecting 51.8% and 26.4% increments, respectively. The improvement of mechanical properties should be mainly attributed to the grain refinement and homogeneous distribution of n-SiCp in the composites. Moreover, a well-bonded interface and the formation of an appropriate amount of interfacial product (MgAl2O4) benefited the material’s mechanical properties.

Damage caused by erosion has been reported in several industries for a wide range of situations. In the present work, a new method is presented to improve the erosion resistance of machine components by biomimetic method. A numerical investigation of solid particle erosion in the standard and biomimetic configuration blade of axial fan is presented. The analysis consists in the application of the discrete phase model, for modeling the solid particles flow, and the Eulerian conservation equations to the continuous phase. The numerical study employs computational fluid dynamics (CFD) software, based on a finite volume method. User-defined function was used to define wear equation. Gas/solid flow axial fan was simulated to calculate the erosion rate of the particles on the fan blades and comparatively analyzed the erosive wear of the smooth surface, the groove-shaped, and convex hull-shaped biomimetic surface axial flow fan blade. The results show that the groove-shaped biomimetic blade antierosion ability is better than that of the other two fan blades. Thoroughly analyze of antierosion mechanism of the biomimetic blade from many factors including the flow velocity contours and flow path lines, impact velocity, impact angle, particle trajectories, and the number of collisions.

Twin-roll casting AZ31 Mg alloy sheets have been fabricated by normal unidirectional-rolling, head-to-tail rolling, and clock-rolling, respectively. It has been demonstrated that head-to-tail rolling is the most effective to refine the microstructure and weaken the basal texture among the three rolling routes. Excellent integrated tensile properties can be obtained by the head-to-tail rolling. The yield strength, ultimate tensile strength, and plastic elongation are 196 MPa, 301 MPa, and 28.9%, respectively. The strength can benefit from the fine grains (average value of 4.0 μm) of the AZ31 alloy processed by the head-to-tail rolling route, while the excellent plastic elongation is achieved owing to the weakened basal texture besides the fine grains. Results obtained here can be used as a basis for further study of some simple rolling methods, which is critical to the development of Mg alloys with high strength and plasticity.

It is found that Li2Sb compound can act as the nucleus of primary Mg2Si during solidification, by which the particle size of primary Mg2Si decreased from ~300 to ~15–25 μm. Owing to the synergistic effect of the Li2Sb nucleus and adsorption-poisoning of Li atoms, the effect of complex modification of Li-Sb on primary Mg2Si was better than that of single modification of Li or Sb. When Li-Sb content increased from 0 to 0.2 and further to 0.5 wt.%, coarse dendrite changed to defective truncated octahedron and finally to perfect truncated octahedral shape. With the addition of Li and Sb, ultimate compression strength (UCS) of Al-20Mg2Si alloys increased from ~283 to ~341 MPa and the yield strength (YS) at 0.2% offset increased from ~112 to ~179 MPa while almost no change was seen in the uniform elongation. Our study offers a simple method to control the morphology and size of primary Mg2Si, which will inspire developing new Al-Mg-Si alloys with improved mechanical properties.