查看更多>>摘要：Based on experiments and first-principles calculations,the microstructures and mechanical properties of as-cast and solution treated Mg-10Gd-4Y-xZn-0.6Zr(x=0,1％,2％in mass fraction)alloys are investigated.The transformation process of long-period stacking ordered(LPSO)structure during solidification and heat treatment and its effect on the mechanical properties of experimental alloys are discussed.Results reveal that the stacking faults and 18R LPSO phases appear in the as-cast Mg-10Gd-4Y-1Zn-0.6Zr and Mg-10Gd-4Y-2Zn-0.6Zr alloys,respectively.After solution treatment,the stacking faults and 18R LPSO phase transform into 14H LPSO phase.The enthalpies of formation and reaction en-ergy of 14H and 18R LPSO are calculated based on first-principles.Results show that the alloying ability of 18R is stronger than that of 14H.The reaction energies show that the 14H LPSO phase is more stable than the 18R LPSO.The elastic properties of the 14H and 18R LPSO pha-ses are also evaluated by first-principles calculations,and the results are in good agreement with the experimental results.The precipitation of LPSO phase improves the tensile strength,yield strength and elongation of the alloy.After solution treatment,the Mg-10Gd-4Y-2Zn-0.6Zr alloy has the best mechanical properties,and its ultimate tensile strength and yield strength are 278.7 MPa and 196.4 MPa,respectively.The elonga-tion of Mg-10Gd-4Y-2Zn-0.6Zr reaches 15.1,which is higher than that of Mg-10Gd-4Y0.6Zr alloy.The improving mechanism of elastic modu-lus by the LPSO phases and the influence on the alloy mechanical properties are also analyzed.
Muhammad Ali KhanAnanda Repycha SafiraMosab KaseemArash Fattah-alhosseini...
2068-2088页
查看更多>>摘要：This study explores the potential of LDH flakes decorated with metallic oxide nanoparticles to function as both anti-corrosion barriers against chloride anions and heterogeneous photocatalysts for tetracycline degradation under visible light.The process involves modifying the primarily MgO-based inorganic porous film by growing a MgFe LDH film,followed by the individual and dual incorporation of SnO2 and WO3 nanopar-ticles.The dual incorporation of these nanoparticles into the LDH matrix leads to synergistic interactions,effectively sealing pre-existing defects within LDH flakes and facilitating the in-situ formation of catalytic sites through oxidation and the induction of surface oxygen vacancy defects,which synergistically contribute to the enhancement of both electrochemical and photocatalytic activities.The enhanced electrochemical stability is reflected in a significant reduction in corrosion current density by 4 orders of magnitude compared to unmodified porous film.Additionally,the decorated film demonstrates sustained photocatalytic functionality,achieving significant degradation(95.5％)of tetracycline within two hours.This study presents a novel approach,highlighting the dual effectiveness of LDHs decorated by dual metal oxides as an anti-corrosive a-gent and photocatalyst,with promising implications for environmental remediation and wastewater purification.
查看更多>>摘要：The practical applications of magnesium(Mg)alloys are usually beset by their relatively low strength and limited ductility.Herein we attempt to fabricate hexagonal BN nanoplatelet(BNNP)reinforced ZK61 magnesium composites using a combination of spark plasma sintering and fric-tion stir processing.The resulting composites exhibit microstructural characteristics of homogeneous dispersion of BNNP in Mg matrix with re-fined equiaxed grains and(0002)basal texture roughly surrounding the pin column surface.Transmission electron microscopy observation illus-trates that trace amounts of Mg3N2 and MgB2 form at BNNP-Mg interface,in which Mg3N2 locates at the basal plane of a BNNP and MgB2 grows at its open edge.The spatial distribution of Mg3N2 and MgB2 facilitates interfacial wetting and stronger BNNP-Mg interface in such a way that interfacial products act as anchors bonding between them.In comparison with monolithic ZK61 alloy,the BNNP/ZK61 composites dis-play simultaneous improvements in yield strength,hardness and ductility,achieving good strength-ductility balance.This research is expected to shed some light on BNNP potentials for designing and producing magnesium composites with high strength and good ductility.
查看更多>>摘要：In this study,we explored the deformation mechanisms of Mg single crystals using a combination of scanning electron microscopy and elec-tron backscattered diffraction in conjunction with a dedicated four-point bending tester.We prepared two single-crystal samples,oriented along the<(11)20>and<10(1)0>directions,to assess the mechanisms of deformation when the initial basal slip was suppressed.In the<(11)20>sample,the primary {10(1)2 } twin(T1)was confirmed along the<(11)20>direction of the sample on the compression side with an increase in bending stress.In the<10(1)0>sample,T1 and the secondary twin(T2)were confirmed to be along the<(11)20>direction,with an orientation of±60° with respect to the bending stress direction,and their direction matched with(0001)in T1 and T2.This result implies that crystallographically,the basal slip occurs readily.In addition,the<10(1)0>sample showed the double twin in T1 on the compression side and the tertiary twin along the<10(1)0>direction on the tension side.These results demonstrated that the maximum bending stress and displacement changed significantly under the bend loading because the deformation mechanisms were different for these single crystals.Therefore,the correlation between bending behavior and twin orientation was determined,which would be helpful for optimizing the bending properties of Mg-based materials.
查看更多>>摘要：This paper provided an effective method to further improve the mechanical properties of the AZ80+0.4％Ce magnesium alloy wheel spoke.The effect of high strength and ductility was obtained with a yield strength of 295.36 MPa,an elongation of 10％,by the combination of pre-de-formation(7％deformation)and two-stage aging treatment(120 ℃/9 h+175 ℃/24 h).The evolution of the microstructure and properties of the alloy was explored under the coupling conditions of different pre-deformation degrees and multi-stage aging.The results show that,pre-de-formation introduced a large number of(10(1)2)tensile twinning and dislocations,which greatly promoted the probability of continuous precipi-tates(CPs)appearing.On the contrary,the discontinuous precipitates(DPs)were limited by the vertical and horizontal twin structure.As a re-sult,the pre-nucleation method of two-stage aging increased the proportion of CPs by 34％-38％.Owing to the DPs was effectively suppressed,the alloy's yield strength has been greatly improved.Besides,under multi-stage aging,the twin boundaries induce protruding nucleation to form static recrystallization by hindering the migration of dislocations,and the matrix swallows the twins,then the texture gradually tilts from the two poles to the basal plane.As an important supplement,the grain refinement and oblique texture promoted the improvement of the yield strength of the component.
查看更多>>摘要：The aim of this work is to predict,for the first time,the high temperature flow stress dependency with the grain size and the underlaid de-formation mechanism using two machine learning models,random forest(RF)and artificial neural network(ANN).With that purpose,a ZK30 magnesium alloy was friction stir processed(FSP)using three different severe conditions to obtain fine grain microstructures(with average grain sizes between 2 μm and 3 μm)prone to extensive superplastic response.The three friction stir processed samples clearly deformed by grain boundary sliding(GBS)deformation mechanism at high temperatures.The maximum elongations to failure,well over 400％at high strain rate of 10-2 s-1,were reached at 400 ℃ in the material with coarsest grain size of 2.8 μm,and at 300 ℃ for the finest grain size of 2 μm.Neverthe-less,the superplastic response decreased at 350 ℃ and 400 ℃ due to thermal instabilities and grain coarsening,which makes it difficult to assess the operative deformation mechanism at such temperatures.This work highlights that the machine learning models considered,especially the ANN model with higher accuracy in predicting flow stress values,allow determining adequately the superplastic creep behavior including other possible grain size scenarios.
查看更多>>摘要：In this paper,the effect of the Si content on microstructure evolution,mechanical properties,and fracture behavior of the Al-xSi/AZ91D bi-metallic composites prepared by compound casting was investigated systematically.The obtained results showed that all the Al-xSi/AZ91D bi-metallic composites had a metallurgical reaction layer(MRL),whose thickness increased with increasing Si content for the hypoeutectic Al-Si/AZ91D composites,while the hypereutectic Al-Si/AZ91D composites were opposite.The MRL included eutectic layer(E layer),intermetallic compound layer(IMC layer)and transition region layer(T layer).In the IMC layer,the hypereutectic Al-Si/AZ91D composites contained some Si solid solution and flocculent Mg2Si+Al-Mg IMCs phases not presented in the hypoeutectic Al-Si/AZ91D composites.Besides,increasing Si content,the thickness proportion of the T layer increased,forming an inconsistent preferred orientation of the MRL.The shear strengths of the Al-xSi/AZ91D bimetallic composites enhanced with increasing Si content,and the Al-15Si/AZ91D composite obtained a maximum shear strength of 58.6 MPa,which was 73.4％higher than the Al-6Si/AZ91D composite.The fractures of the Al-xSi/AZ91D bimetallic composites transformed from the T layer into the E layer with the increase of the Si content.The improvement of the shear strength of the Al-xSi/AZ91D bimetallic composites was attributed to the synergistic action of the Mg2Si particle reinforcement,the reduction of oxidizing inclusions and the ratio of Al-Mg IMCs as well as the orientation change of the MRL.
查看更多>>摘要：In this study,a calcium-phosphate coating was formed on a Mg-Mn-Ce alloy by the plasma electrolytic oxidation(PEO).The antibiotic van-comycin,widely used in the treatment of infections caused by Staphylococcus aureus(S.aureus),was impregnated into the coating.Samples with vancomycin showed high bactericidal activity against S.aureus.The mechanical and electrochemical properties of the formed coatings were studied,as well as in vitro cytotoxicity tests and in vivo tests on mature male rats were performed.According to SEM,EDS,XRD and XPS data,coatings had a developed morphology and contained hydroxyapatite,which indicates high biocompatibility.The analysis of roughness of coat-ings without and with vancomycin did not reveal any differences,confirming the high roughness of the samples.During electrochemical tests,an increase in corrosion resistance by more than two times after the application of PEO coatings was revealed.According to the results of an in vi-vo study,after 28 days of the implantation of samples with calcium phosphate PEO coating and vancomycin,no signs of inflammation were ob-served,while an inflammatory reaction developed in the area of implantation of bare alloy,followed by encapsulation.Antibiotic release tests from the coatings show a sharp decrease in the concentration of the released antibiotic on day 7 and then a gradual decrease until day 28.Throughout the experiment,no significant deviations in the condition and behavior of the animals were observed;clinical tests did not reveal a systemic toxic reaction.
查看更多>>摘要：Laser-arc hybrid welding of AZ31B magnesium alloy was carried out,the effects of welding parameters on weld formation,microstructure homogeneity and mechanical properties were investigated.The results showed that laser-arc hybrid welding was beneficial to improve the weld formation of magnesium alloy by inhibiting the defect of undercut and pores.The weld microstructure was mainly columnar grains neighboring the fusion line and equiaxed grains at the weld center.It was interesting that the grain size at the upper arc zone was smaller than that at the low-er laser zone,with the difference mainly affected by laser power rather than welding current and welding speed.The welding parameters were optimized as laser power of 3.5 kW,welding current of 100 A and welding speed of 1.5 m·min-1.In this case,the weld was free of undercut and pores,and the tensile strength and elongation rate reached 252 MPa and 11.2％,respectively.Finally,the microstructure homogeneity was illustrated according to the heat distribution,and the evolution law of tensile properties was discussed basing on the weld formation and micro-structure characteristics.
Umer Masood ChaudryHafiz Muhammad Rehan TariqNooruddin AnsariSoo Yeol Lee...
2192-2206页
查看更多>>摘要：This study investigates the influence of CaO(0.5％,1.0％,mass fraction)alloying on the microstructural evolution,texture development and deformation behavior of AZ61 magnesium alloy.The uniaxial tension tests at room(RT)and cryogenic(CT,-150 ℃)temperature were per-formed to investigate the twinability and dislocation behavior and its consequent effect on flow stress,ductility and strain hardening rate.The re-sults showed that the AZ61-1CaO exhibited superior strength/ductility synergy at RT with a yield strength(YS)of 223 MPa and a ductility of 23％as compared to AZ61(178 MPa,18.5％)and AZ61-0.5CaO(198 MPa,21％).Similar trend was witnessed for all the samples during CT deformation,where increase in the YS and decrease in ductility were observed.The Mtex tools based in-grain misorientation axis(IGMA)anal-ysis of RT deformed samples revealed the higher activities of prismatic<a>slip in AZ61-CaO,which led to superior ductility.Moreover,subse-quent EBSD analysis of CT deformed samples showed the increased fraction of fine {10-12} tension twins and nucleation of multiple {10-12}twin variants caused by higher local stress concentration at the grain boundaries,which imposed the strengthening by twin-twin interaction.Last-ly,the detailed investigations on strengthening contributors showed that the dislocation strengthening has the highest contribution towards strength in all samples.
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