High-temperature and short-time(HTST)solution heat treatment combined with non-isothermal aging(NIA)was employed to regulate the microstructure and properties of Al−4.5Mg−2.0Zn−0.3Ag alloy.Results indicate that HTST s...High-temperature and short-time(HTST)solution heat treatment combined with non-isothermal aging(NIA)was employed to regulate the microstructure and properties of Al−4.5Mg−2.0Zn−0.3Ag alloy.Results indicate that HTST solution heat treatment can not only retain partial deformation dislocations,but inhibit the recrystallization behavior and increase the proportion of low-angle grain boundaries(LAGBs).In the subsequent NIA process,HTST solution heat treatment combined with NIA is instrumental in restraining the degradation of dislocations and promoting precipitation of nano-scale T'-Mg_(32)(Al,Zn,Ag)49 phase,which improves the strength of the alloy greatly.In addition,a higher fraction of LAGBs and the discontinuous distribution of grain boundary precipitates caused by this novel technology meliorate the corrosion resistance of Al−4.5Mg−2.0Zn−0.3Ag alloy.展开更多
To improve the corrosion resistance of biodegradable Mg alloys,WE43 alloys were implanted with Fe,Ti,Zn and Zr ions at the same implantation dose.The surface morphology,valence state of elements,nano-hardness(NH),elas...To improve the corrosion resistance of biodegradable Mg alloys,WE43 alloys were implanted with Fe,Ti,Zn and Zr ions at the same implantation dose.The surface morphology,valence state of elements,nano-hardness(NH),elastic modulus(EM),degradation rate and in vitro cell experiments of the modified WE43 alloys were systematically studied.A modified layer composed of Mg,MgO,the implanted elements and their oxides was formed on the modified alloys.Since high-speed metal ions caused severe surface lattice damage,the surface hardness of the substrate considerable increased.Electrochemical tests demonstrated a substantial enhancement in the corrosion resistance of the modified alloys via the implantation of Ti and Zr ions,resulting in a reduction of the corrosion current density to 88.1±9.9 and 15.6±11.4μA cm^(−2),respectively,compared with the implantation of Fe and Zn ions.Biocompatibility tests showed that the implantation of Fe,Ti,Zn and Zr ions enhanced the anticoagulant and hemolytic resistance of the WE43 alloy.All surface-modified samples showed negligible cytotoxicity(0-1)at 12.5%extract concentration.Moreover,the alloys implanted with Fe,Ti and Zn ions significantly promoted proliferation of human umbilical vein endothelial cells(HUVEC)compared with the unmodified alloy.The results demonstrate that Ti ion implantation is the best choice for WE43 alloy modification to achieve outstanding corrosion resistance and biocompatibility.展开更多
In this work,through performing microstructural characterization,tensile testing and failure analysis,the influence of electrochemical hydrogen charging on the microstructure and mechanical behavior of an as-cast Mg-8...In this work,through performing microstructural characterization,tensile testing and failure analysis,the influence of electrochemical hydrogen charging on the microstructure and mechanical behavior of an as-cast Mg-8wt.%Li alloy was investigated.It revealed that after being hydrogen charged at 50 mA/cm2 for respectively 3 h,6 h and 18 h in 0.1 M NaCl solution,obvious HID occurred and the damage degree was gradually increased with the hydrogen charging time.For the sample being hydrogen charged for 3 h,micro pores with the diameter ranging from 10~30µm were formed and preferentially present inα-Mg phase.Moreover,micro cracks with the length ranging from 10~50µm mainly initiated inα-Mg phase,atα-Mg/β-Li interfaces and the peripheries of pores.With the increase of hydrogen charging time,the numbers of pores and cracks were obviously increased.Tensile results revealed that the hydrogen charging can simultaneously decrease the tensile strength and ductility of the alloy.Compared with the uncharged sample,the tensile yield strength,ultimate tensile strength and the elongation ratio to failure were respectively reduced by 5.7%,7.3%,31.7%for the 3h-charged sample and 24.6%,24.8%,67.0%for the 18h-charged sample.Failure analysis indicated that hydrogen charging can induce the brittle cracking of the alloy and the size of brittle cracking region being composed of quasi-cleavage facets and interfacial cracks on the fracture surfaces was increased with the hydrogen charging time.展开更多
Through exploring the stress corrosion cracking(SCC)behaviors of the as-cast Mg-8%Li and Mg-8%Li-6%Zn-1.2%Y alloys in a 0.1 M NaCl solution,it revealed that the SCC susceptibility index(I_(SCC))of the Mg-8%Li alloy wa...Through exploring the stress corrosion cracking(SCC)behaviors of the as-cast Mg-8%Li and Mg-8%Li-6%Zn-1.2%Y alloys in a 0.1 M NaCl solution,it revealed that the SCC susceptibility index(I_(SCC))of the Mg-8%Li alloy was 47%,whilst the I_(SCC)of the Mg-8%Li-6%Zn-1.2%Y alloy was 68%.Surface,cross-sectional and fractography observations indicated that for the Mg-8%Li alloy,theα-Mg/β-Li interfaces acted as the preferential crack initiation sites and propagation paths during the SCC process.With regard to the Mg-8%Li-6%Zn-1.2%Y alloy,the crack initiation sites included the I-phase and the interfaces of I-phase/β-Li andα-Mg/β-Li,and the preferential propagation paths were the I-phase/β-Li andα-Mg/β-Li interfaces.Moreover,the SCC of the two alloys was concerned with hydrogen embrittlement(HE)mechanism.展开更多
Ultrasonic vibration was introduced into the casting of quasicrystal-reinforced magnesium alloy ZW61.The microstructure,mechanical properties,and corrosion resistance were studied.The dual-frequency ultrasonic field(D...Ultrasonic vibration was introduced into the casting of quasicrystal-reinforced magnesium alloy ZW61.The microstructure,mechanical properties,and corrosion resistance were studied.The dual-frequency ultrasonic field(DUF)treatment reduced the α-Mg grain size from 502μm to 69μm,and the aggregated lamellar I-phase was refined into tiny dot-like shapes with a smaller area fraction.Static corrosion and electrochemical tests indicated that DUF decreased the corrosion rate from 10 mm·y^(-1)to 3mm·y^(-1)with a denser protective oxide film.DUF not only significantly enlarged the effective cavitation area but also reduced the dependence of transient cavitation on the initial bubble radius.The ratio R_(max)^(3)/t_(c) was used to qualitatively characterize the cavitation strength,and cavitation dynamics calculations indicated that DUF had higher cavitation strength compared to single-frequency ultrasonic field(SUF).An equation for corrosion rate versus microstructural parameters(grain size,second phase fraction,potential difference)was developed,which could well predict the corrosion rate of magnesium alloy ZW61 without and with different ultrasonic vibrations.展开更多
The super high strength aluminum alloy ingots with 100 mm in diameter were cast by the process of low-frequency electromagnetic horizontal continuous casting (LFEHC) and the effect of electromagnetic field on the as-c...The super high strength aluminum alloy ingots with 100 mm in diameter were cast by the process of low-frequency electromagnetic horizontal continuous casting (LFEHC) and the effect of electromagnetic field on the as-cast microstructure was studied. Results show that microstructure of the sample prepared by the LFEHC process was greatly refined. Microstructures at the border and the center of the ingots were fine, uniform and rosette-shaped. Electromagnetic frequency plays a key role in microstructure refining. Fine and uniform microstructures can be obtained with optimal electromagnetic frequency. In this experiment, under a frequency of 30 Hz the microstructure was the finest and the most uniform.展开更多
Phased array ultrasonic testing, an effective ultrasonic testing(UT) technology, has been widely used in steel inspection because of its high accuracy, sensitivity, and efficiency. However, as its application in as-ca...Phased array ultrasonic testing, an effective ultrasonic testing(UT) technology, has been widely used in steel inspection because of its high accuracy, sensitivity, and efficiency. However, as its application in as-cast magnesium alloys has just begun, more research is needed. Considering the important role of the gain compensation in quantifying defects in magnesium alloys by ultrasonic phased array technology, the effects of microstructure, the position, size, and overlap of defects, and boundary distance(distance from the defect position to the side surface of the test casting) on gain compensation of as-cast AZ80 and AZ31 magnesium alloys were studied. Results show the gain compensation increases with the increase of grain size. There is a strict linear positive correlation between gain compensation and defect depth, but such relationship no longer exists due to the defects overlap, orientation and boundary distance. In addition, there is a strict linear negative correlation between the gain compensation and defect size.展开更多
A transient 3D model was established to investigate the effect of spatial interaction of ultrasounds on the dual-frequency ultrasonic field in magnesium alloy melt.The effects of insertion depth and tip shape of the u...A transient 3D model was established to investigate the effect of spatial interaction of ultrasounds on the dual-frequency ultrasonic field in magnesium alloy melt.The effects of insertion depth and tip shape of the ultrasonic rods,input pressures and their ratio on the acoustic field distribution were discussed in detail.Additionally,the spacing,angle,and insertion depth of two ultrasonic rods significantly affect the interaction between distinct ultrasounds.As a result,various acoustic pressure distributions and cavitation regions are obtained.The spherical rods mitigate the longitudinal and transversal attenuation of acoustic pressure and expand the cavitation volume by 53.7%and 31.7%,respectively,compared to the plate and conical rods.Increasing the input pressure will enlarge the cavitation region but has no effect on the acoustic pressure distribution pattern.The acoustic pressure ratio significantly affects the pressure distribution and the cavitation region,and the best cavitation effect is obtained at the ratio of 2:1(P15:P20).展开更多
The effects of two types of magnetic fields,namely harmonic magnetic field(HMF)and pulse magnetic field(PMF)on magnetic flux density,Lorentz force,temperature field,and microstructure of high purity Cu were studied by...The effects of two types of magnetic fields,namely harmonic magnetic field(HMF)and pulse magnetic field(PMF)on magnetic flux density,Lorentz force,temperature field,and microstructure of high purity Cu were studied by numerical simulation and experiment during electromagnetic direct chill casting.The magnetic field is induced by a magnetic generation system including an electromagnetic control system and a cylindrical crystallizer of 300 mm in diameter equipped with excitation coils.A comprehensive mathematical model for high purity Cu electromagnetic casting was established in finite element method.The distributions of magnetic flux density and Lorentz force generated by the two magnetic fields were acquired by simulation and experimental measurement.The microstructure of billets produced by HMF and PMF casting was compared.Results show that the magnetic flux density and penetrability of PMF are significantly higher than those of HMF,due to its faster variation in transient current and higher peak value of magnetic flux density.In addition,PMF drives a stronger Lorentz force and deeper penetration depth than HMF does,because HMF creates higher eddy current and reverse electromagnetic field which weakens the original electromagnetic field.The microstructure of a billet by HMF is composed of columnar structure regions and central fine grain regions.By contrast,the billet by PMF has a uniform microstructure which is characterized by ultra-refined and uniform grains because PMF drives a strong dual convection,which increases the uniformity of the temperature field,enhances the impact of the liquid flow on the edge of the liquid pool and reduces the curvature radius of liquid pool.Eventually,PMF shows a good prospect for industrialization.展开更多
To improve the quality of 7050 aluminum alloy ingots, low-frequency electromagnetic （LFE） field was applied during the conventional hot-top casting process. Macrostructures and microstructures of the ingots by the c...To improve the quality of 7050 aluminum alloy ingots, low-frequency electromagnetic （LFE） field was applied during the conventional hot-top casting process. Macrostructures and microstructures of the ingots by the conventional and LFE hot-top casting processes were studied. The experimental results show that when the LFE field is turn off during the hot-top casting process, cold folding appears, and the as-cast structure becomes very coarse. Additionally, the thickness of the shell zone is much thinner during the low-frequency electromagnetic hot-top casting process than that during the conventional hot-top casting process. Some reasons for low-frequency electromagnetic field improving the surface quality, refining the structure of the ingot, and minimizing the thickness of the shell zone have been studied.展开更多
Due to lattice reorientation,grain segmentation,induced recrystallization,twins play a very important role in regulating texture,refining grains,improving mechanical properties and corrosion resistance,and has receive...Due to lattice reorientation,grain segmentation,induced recrystallization,twins play a very important role in regulating texture,refining grains,improving mechanical properties and corrosion resistance,and has received more extensive attention.Numerous studies have shown that{10-12}<10-11>tensile twins(TTWs)are easily activated in large quantities due to the lower critical resolve shear stresses(CRSS).Introduction of TTWs under uniaxial compression improved the strength,ductility,and formability of magnesium(Mg)alloys.Moreover,TTWs produced by multi-directional impact forging(MDIF)can optimize the microstructure by dividing grains and promoting recrystallization,resulting in significant improvement of mechanical properties.Although{10-11}<10-12>compressive twins(CTWs)and{10-11}-{10-12}double twins(DTWs)can promote dynamic recrystallization(DRX),they are also favorable nucleation sites for cracks.In addition,the type and volume fraction of twins can affect the corrosion resistance,and they also play different roles in the corrosion process of different Mg alloys.Twins have shown great potential for improving structure and properties,but a comprehensive and critical discussion of twins in Mg alloys is still lacking.Therefore,based on previous studies,this article reviews the common types and variants of twins in Mg alloys,influencing factors,and their effects on the microstructure,mechanical properties and corrosion resistance.In addition,some interesting ideas are being proposed for further research.展开更多
Four Mg–Gd–Y–Nd–Zr alloys were prepared by mold casting to investigate the effects of Nd/Gd ratios on microstructures and mechanical properties.The as-cast alloys mainly consist ofα-Mg andβ-Mg5(GdYNd).Volume fra...Four Mg–Gd–Y–Nd–Zr alloys were prepared by mold casting to investigate the effects of Nd/Gd ratios on microstructures and mechanical properties.The as-cast alloys mainly consist ofα-Mg andβ-Mg5(GdYNd).Volume fractions of the second phase increase and grains were slightly refined with the rising Nd/Gd ratio,when the alloying addition is equal.Meanwhile,fibers of second phase also increase in the extruded alloys when the Nd/Gd value increases.However,the Nd/Gd ratio could hardly influence the mechanical properties of the extruded alloys.The aging hardening response of the extruded alloy differs due to different Nd/Gd ratios.The potential mechanisms have also been discussed in detail.展开更多
For obtaining the finer grains of magnesium alloy,a novel combined pulsed magnetic field with different initial phases,also called out-ofphase pulsed magnetic field(OPPMF),was applied to study the solidification struc...For obtaining the finer grains of magnesium alloy,a novel combined pulsed magnetic field with different initial phases,also called out-ofphase pulsed magnetic field(OPPMF),was applied to study the solidification structure of AZ80 magnesium alloy.The numerical simulation was simultaneously conducted to investigate the refinement mechanisms.The experimental results showed that the macrostructure could be effectively refined by applying external magnetic field.Meanwhile,finer grains were obtained with the higher current intensity.However,the increase of current intensity could only refine the grains to about 0.5 mm.Furthermore,compared to a single pulsed magnetic field(PMF)and alternating series of OPPMF(Connection II),a finer structure was observed when the consecutive series of OPPMF(Connection I)was imposed.In contrast with a single PMF and Connection II,the numerical results showed that the greater axial Lorentz force was obtained under the Connection I,generating the stronger forced flow in the melt.It is believed that abundant nuclei could detach from the mold wall and move faster into the interior melt due to the stronger forced flow;besides,the lower superheat and greater temperature uniformity in bulk melt were realized,accounting for the finest structures under the Connection I.展开更多
The mechanical properties and microstructures of 6013 alloy after different thermomechanical treatments were investigated. The detailed dislocation configurations after deformation and morphologies of age hardening pr...The mechanical properties and microstructures of 6013 alloy after different thermomechanical treatments were investigated. The detailed dislocation configurations after deformation and morphologies of age hardening precipitates were examined through transmission electron microscopy （TEM）. The experimental results show that the thermomechanical treatment can significantly enhance the strength of 6013 alloy, and has a similar influence trend on single and two-step aging behaviors. With the increasing deformation ratio, the peak-hardness （HVmax） increases, the time to HV shortens, and the density of tangled dislocation network increases. The aging precipitates become larger and inhomogeneous by applying thernomechanical treatment.展开更多
The Mg-xGd-2.6Nd-0.5Zn-0.5Zr(x=0,3.0,4.5 and 6.0,wt.%)alloys were prepared by gravity casting and then T6 treatment.Microstructures of the alloy were observed using optical microscopy and scanning electron microscopy....The Mg-xGd-2.6Nd-0.5Zn-0.5Zr(x=0,3.0,4.5 and 6.0,wt.%)alloys were prepared by gravity casting and then T6 treatment.Microstructures of the alloy were observed using optical microscopy and scanning electron microscopy.Results show that the as-cast alloys contained network Mg3Gd phases,blocky and needle-like Mg12(Nd,Gd)phases.The a(Zr)particle inclusions in the a(Mg)matrix are also observed.Content of the secondary phases decreases as Gd content increases.Tensile test results show that the tensile and yield strengths of all the alloys increase as Gd content increases under the as-cast and T6 conditions,but the elongation exhibits the opposite trend.The blocky Mg12(Nd,Gd)phases appear and act as crack initiator and deteriorates the experimental alloys’ductility with the increase of Gd content,especially as Gd content increases to 6.0 wt.%,so the Mg-6.0Gd-2.6Nd-0.5Zn-0.5Zr alloy has the lowest elongation value compared to the other alloys studied.After T6 treatment,the Mg-4.5Gd-2.6Nd-0.5Zn-0.5Zr alloy exhibits the optimal mechanical properties both at room temperature and 250℃.展开更多
The ingot was prepared by direct-chill(DC)casting technology with different casting speeds under the influence of intensive melt shearing to explore the effect of casting speed and intensive melt shearing on the float...The ingot was prepared by direct-chill(DC)casting technology with different casting speeds under the influence of intensive melt shearing to explore the effect of casting speed and intensive melt shearing on the floating grains and negative centerline segregation.The results indicate that the application of intensive melt shearing in DC casting process can distribute the floating grains uniformly,reduce the area fraction of the floating grains,alleviate the negative centerline segregation,and improve the uniformity of temperature field in the sump.It is also suggested that under the influence of intensive melt shearing,the casting speed plays a crucial role in the amounts and distribution of floating grains.At low casting speed,the intensive melt shearing can significantly reduce the area fraction of the floating grains and distribute them uniformly throughout the ingot.However,this effect gradually disappears with the increase of casting speed.展开更多
In this work,the discharge properties and electrochemical behaviors of as-cast AZ80-La-Gd anode for Mg-air battery have been investigated and compared with the AZ80 anode.The microstructure evolution,electrochemical b...In this work,the discharge properties and electrochemical behaviors of as-cast AZ80-La-Gd anode for Mg-air battery have been investigated and compared with the AZ80 anode.The microstructure evolution,electrochemical behaviors and surface morphologies after discharge have been discussed to connect the discharge properties.The results indicate that the modified AZ80-La-Gd is an outstanding candidate for anode for Mg-air batter,which has high cell voltage,stable discharge curves,good specific capacity and energy,and good anodic efficiency.It exhibits the best anodic efficiency,specific capacity and energy of 76.45%,1703.6 mAh·g^(-1)and 2186.3 mWh·g^(-1),respectively,which are20.24%,18.92%and 25.71%higher than values for AZ80 anode.Such excellent discharge performance is attributed to the Al-RE particles.They refine the Mg_(17)Al_(12)phase and therefore improve the self-corrosion resistance and desorption ability of AZ80 anode.展开更多
Large and segregated primary Si particles may drastically decrease the mechanical properties of AI-Si alloys. To solve this problem, a P-Cr complex modifier was added into the alloy, and the effects of P-Cr complex mo...Large and segregated primary Si particles may drastically decrease the mechanical properties of AI-Si alloys. To solve this problem, a P-Cr complex modifier was added into the alloy, and the effects of P-Cr complex modification and solidification conditions on the microstructure of hypereutectic Al-Si alloys casting produced in wedge-shaped copper mould were studied. The thermal analysis technique was applied to calculate the cooling rate during solidification. The microstructures were observed by means of optical and scanning electron microscopies. Results showed that the primary Si segregates in the as-cast hypereutectic AI-Si alloys. The segregation of primary Si can be inhibited by adding a P＋Cr complex modifier and increasing the cooling rate during solidification. The refinement of primary Si particles by P＋Cr complex modification is due to the formation of CrSi2 and AlP particles which act as the heterogeneous nuclei for the primary Si phase. The segregation of Si was also inhibited through the adherence of heavier CrSi2 particles to the primary Si particles.展开更多
Mg-9Gd-3Y-1.5Zn-0.8Zr alloys own high strength,good heat and corrosion resistance.However,it is difficult for the fabrication of large-scale billets,due to the poor deformation ability and strong hot-crack tendency.Th...Mg-9Gd-3Y-1.5Zn-0.8Zr alloys own high strength,good heat and corrosion resistance.However,it is difficult for the fabrication of large-scale billets,due to the poor deformation ability and strong hot-crack tendency.This work investigated the casting process on the microstructures and flow stress behaviors of the semi-continuous casting billets for the fabrication of large-scale Mg-9Gd-3Y-1.5Zn-0.8Zr billets.The casting process(electromagnetic intensity and casting speed)shows outstanding effects on the microstructures and flow stress behavior of the billets.The billets with the specific casting process(I=68 A,V=65 mm/min)exhibit uniform microstructures and good deformation uniformity.展开更多
Three as-cast and as-extruded Mg-5Zn-x Y-0.6Zr(x=5 wt%, 8 wt%, 11 wt%) alloys were prepared, and the effects of Y content on the microstructures and mechanical properties of the alloys were investigated. The results s...Three as-cast and as-extruded Mg-5Zn-x Y-0.6Zr(x=5 wt%, 8 wt%, 11 wt%) alloys were prepared, and the effects of Y content on the microstructures and mechanical properties of the alloys were investigated. The results show that the investigated Mg-Zn-Y-Zr alloys mainly consist of a-Mg, X-Mg12 YZn and minor amount of W-Mg_3Y_2Zn_3 phases. The volume fraction of X-Mg_(12) YZn phase increases and that of W-Mg_3Y_2Zn_3 phase decreases with the rising of Y content in the alloys. The as-extruded Mg-5Zn-11Y-0.6Zr alloy owns the optimal ultimate tensile strength and yield strength of 429 and 351 MPa, respectively. Mg-5Zn-5Y-0.6Zr alloy owns the maximum elongation of 13.6%.展开更多
基金National Natural Science Foundation of China(Nos.52204400,52204401)Natural Science Foundation of Hebei Province,China(No.E2022203033)。
文摘High-temperature and short-time(HTST)solution heat treatment combined with non-isothermal aging(NIA)was employed to regulate the microstructure and properties of Al−4.5Mg−2.0Zn−0.3Ag alloy.Results indicate that HTST solution heat treatment can not only retain partial deformation dislocations,but inhibit the recrystallization behavior and increase the proportion of low-angle grain boundaries(LAGBs).In the subsequent NIA process,HTST solution heat treatment combined with NIA is instrumental in restraining the degradation of dislocations and promoting precipitation of nano-scale T'-Mg_(32)(Al,Zn,Ag)49 phase,which improves the strength of the alloy greatly.In addition,a higher fraction of LAGBs and the discontinuous distribution of grain boundary precipitates caused by this novel technology meliorate the corrosion resistance of Al−4.5Mg−2.0Zn−0.3Ag alloy.
基金supported by National Natural Science Foundation of China(52271117)Educational Commission of Hunan Province of China(23A0107)High Technology Research and Development Program of Hunan Province of China(2022GK4038).
文摘To improve the corrosion resistance of biodegradable Mg alloys,WE43 alloys were implanted with Fe,Ti,Zn and Zr ions at the same implantation dose.The surface morphology,valence state of elements,nano-hardness(NH),elastic modulus(EM),degradation rate and in vitro cell experiments of the modified WE43 alloys were systematically studied.A modified layer composed of Mg,MgO,the implanted elements and their oxides was formed on the modified alloys.Since high-speed metal ions caused severe surface lattice damage,the surface hardness of the substrate considerable increased.Electrochemical tests demonstrated a substantial enhancement in the corrosion resistance of the modified alloys via the implantation of Ti and Zr ions,resulting in a reduction of the corrosion current density to 88.1±9.9 and 15.6±11.4μA cm^(−2),respectively,compared with the implantation of Fe and Zn ions.Biocompatibility tests showed that the implantation of Fe,Ti,Zn and Zr ions enhanced the anticoagulant and hemolytic resistance of the WE43 alloy.All surface-modified samples showed negligible cytotoxicity(0-1)at 12.5%extract concentration.Moreover,the alloys implanted with Fe,Ti and Zn ions significantly promoted proliferation of human umbilical vein endothelial cells(HUVEC)compared with the unmodified alloy.The results demonstrate that Ti ion implantation is the best choice for WE43 alloy modification to achieve outstanding corrosion resistance and biocompatibility.
基金supported by the National Natural Science Foundation of China Projects under grant[nos.U21A2049,52071220,51871211,51701129 and 51971054]Liaoning Province's project of“Revitalizing Liaoning Talents”(XLYC1907062)+6 种基金the Doctor Startup Fund of Natural Science Foundation Program of Liaoning Province(no.2019-BS-200)the Strategic New Industry Development Special Foundation of Shenzhen(JCYJ20170306141749970)the funds of International Joint Laboratory for Light Alloys,Liaoning BaiQianWan Talents Program,the Domain Foundation of Equipment Advance Research of 13th Five-year Plan(61409220118)National Key Research and Development Program of China under grant[nos.2017YFB0702001 and 2016YFB0301105]the Innovation Fund of Institute of Metal Research(IMR),Chinese Academy of Sciences(CAS),the National Basic Research Program of China(973 Program)project under grant no.2013CB632205the Fundamental Research Fund for the Central Universities under grant[no.N2009006]Bintech-IMR R&D Program[no.GYY-JSBU-2022-009].
文摘In this work,through performing microstructural characterization,tensile testing and failure analysis,the influence of electrochemical hydrogen charging on the microstructure and mechanical behavior of an as-cast Mg-8wt.%Li alloy was investigated.It revealed that after being hydrogen charged at 50 mA/cm2 for respectively 3 h,6 h and 18 h in 0.1 M NaCl solution,obvious HID occurred and the damage degree was gradually increased with the hydrogen charging time.For the sample being hydrogen charged for 3 h,micro pores with the diameter ranging from 10~30µm were formed and preferentially present inα-Mg phase.Moreover,micro cracks with the length ranging from 10~50µm mainly initiated inα-Mg phase,atα-Mg/β-Li interfaces and the peripheries of pores.With the increase of hydrogen charging time,the numbers of pores and cracks were obviously increased.Tensile results revealed that the hydrogen charging can simultaneously decrease the tensile strength and ductility of the alloy.Compared with the uncharged sample,the tensile yield strength,ultimate tensile strength and the elongation ratio to failure were respectively reduced by 5.7%,7.3%,31.7%for the 3h-charged sample and 24.6%,24.8%,67.0%for the 18h-charged sample.Failure analysis indicated that hydrogen charging can induce the brittle cracking of the alloy and the size of brittle cracking region being composed of quasi-cleavage facets and interfacial cracks on the fracture surfaces was increased with the hydrogen charging time.
基金the National Natural Science Foundation of China Projects under Grant[Nos.51871211,U21A2049,52071220,51701129 and 51971054]Liaoning Province’s project of"Revitalizing Liaoning Talents"(XLYC1907062)+10 种基金the Doctor Startup Fund of Natural Science Foundation Program of Liaoning Province(No.2019-BS-200)the Strategic New Industry Development Special Foundation of Shenzhen(JCYJ20170306141749970)the funds of International Joint Laboratory for Light AlloysLiaoning Bai Qian Wan Talents Programthe Domain Foundation of Equipment Advance Research of 13th Five-year Plan(61409220118)National Key Research and Development Program of China under Grant[Nos.2017YFB0702001 and 2016YFB0301105]the Innovation Fund of Institute of Metal Research(IMR)Chinese Academy of Sciences(CAS)the National Basic Research Program of China(973 Program)project under Grant No.2013CB632205the Fundamental Research Fund for the Central Universities under Grant[No.N2009006]Bintech-IMR R&D Program[No.GYY-JSBU-2022-009]。
文摘Through exploring the stress corrosion cracking(SCC)behaviors of the as-cast Mg-8%Li and Mg-8%Li-6%Zn-1.2%Y alloys in a 0.1 M NaCl solution,it revealed that the SCC susceptibility index(I_(SCC))of the Mg-8%Li alloy was 47%,whilst the I_(SCC)of the Mg-8%Li-6%Zn-1.2%Y alloy was 68%.Surface,cross-sectional and fractography observations indicated that for the Mg-8%Li alloy,theα-Mg/β-Li interfaces acted as the preferential crack initiation sites and propagation paths during the SCC process.With regard to the Mg-8%Li-6%Zn-1.2%Y alloy,the crack initiation sites included the I-phase and the interfaces of I-phase/β-Li andα-Mg/β-Li,and the preferential propagation paths were the I-phase/β-Li andα-Mg/β-Li interfaces.Moreover,the SCC of the two alloys was concerned with hydrogen embrittlement(HE)mechanism.
基金financially supported by the National Natural Science Foundation of China(Grant No.51974082 and 52304391)the Programme of Introducing Talents of Discipline Innovation to Universities 2.0(the 111 Project 2.0 of China,No.BP0719037)。
文摘Ultrasonic vibration was introduced into the casting of quasicrystal-reinforced magnesium alloy ZW61.The microstructure,mechanical properties,and corrosion resistance were studied.The dual-frequency ultrasonic field(DUF)treatment reduced the α-Mg grain size from 502μm to 69μm,and the aggregated lamellar I-phase was refined into tiny dot-like shapes with a smaller area fraction.Static corrosion and electrochemical tests indicated that DUF decreased the corrosion rate from 10 mm·y^(-1)to 3mm·y^(-1)with a denser protective oxide film.DUF not only significantly enlarged the effective cavitation area but also reduced the dependence of transient cavitation on the initial bubble radius.The ratio R_(max)^(3)/t_(c) was used to qualitatively characterize the cavitation strength,and cavitation dynamics calculations indicated that DUF had higher cavitation strength compared to single-frequency ultrasonic field(SUF).An equation for corrosion rate versus microstructural parameters(grain size,second phase fraction,potential difference)was developed,which could well predict the corrosion rate of magnesium alloy ZW61 without and with different ultrasonic vibrations.
基金National "863" project (NO.2001AA332030) of China
文摘The super high strength aluminum alloy ingots with 100 mm in diameter were cast by the process of low-frequency electromagnetic horizontal continuous casting (LFEHC) and the effect of electromagnetic field on the as-cast microstructure was studied. Results show that microstructure of the sample prepared by the LFEHC process was greatly refined. Microstructures at the border and the center of the ingots were fine, uniform and rosette-shaped. Electromagnetic frequency plays a key role in microstructure refining. Fine and uniform microstructures can be obtained with optimal electromagnetic frequency. In this experiment, under a frequency of 30 Hz the microstructure was the finest and the most uniform.
基金financially supported by the National Key Research and Development Program of China(Grant No.2017YFB0305504)the National Natural Science Foundation of China(Grant No.51771043)
文摘Phased array ultrasonic testing, an effective ultrasonic testing(UT) technology, has been widely used in steel inspection because of its high accuracy, sensitivity, and efficiency. However, as its application in as-cast magnesium alloys has just begun, more research is needed. Considering the important role of the gain compensation in quantifying defects in magnesium alloys by ultrasonic phased array technology, the effects of microstructure, the position, size, and overlap of defects, and boundary distance(distance from the defect position to the side surface of the test casting) on gain compensation of as-cast AZ80 and AZ31 magnesium alloys were studied. Results show the gain compensation increases with the increase of grain size. There is a strict linear positive correlation between gain compensation and defect depth, but such relationship no longer exists due to the defects overlap, orientation and boundary distance. In addition, there is a strict linear negative correlation between the gain compensation and defect size.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51974082 and 52274377)the Fundamental Research Funds for the Central Universities(Grant No.N2209001)the Programme of Introducing Talents of Discipline Innovation to Universities 2.0(the 111 Project 2.0 of China,Grant No.BP0719037)。
文摘A transient 3D model was established to investigate the effect of spatial interaction of ultrasounds on the dual-frequency ultrasonic field in magnesium alloy melt.The effects of insertion depth and tip shape of the ultrasonic rods,input pressures and their ratio on the acoustic field distribution were discussed in detail.Additionally,the spacing,angle,and insertion depth of two ultrasonic rods significantly affect the interaction between distinct ultrasounds.As a result,various acoustic pressure distributions and cavitation regions are obtained.The spherical rods mitigate the longitudinal and transversal attenuation of acoustic pressure and expand the cavitation volume by 53.7%and 31.7%,respectively,compared to the plate and conical rods.Increasing the input pressure will enlarge the cavitation region but has no effect on the acoustic pressure distribution pattern.The acoustic pressure ratio significantly affects the pressure distribution and the cavitation region,and the best cavitation effect is obtained at the ratio of 2:1(P15:P20).
基金financially supported by the National Key Research and Development Program of China(Grant No.2017YFB0305504)。
文摘The effects of two types of magnetic fields,namely harmonic magnetic field(HMF)and pulse magnetic field(PMF)on magnetic flux density,Lorentz force,temperature field,and microstructure of high purity Cu were studied by numerical simulation and experiment during electromagnetic direct chill casting.The magnetic field is induced by a magnetic generation system including an electromagnetic control system and a cylindrical crystallizer of 300 mm in diameter equipped with excitation coils.A comprehensive mathematical model for high purity Cu electromagnetic casting was established in finite element method.The distributions of magnetic flux density and Lorentz force generated by the two magnetic fields were acquired by simulation and experimental measurement.The microstructure of billets produced by HMF and PMF casting was compared.Results show that the magnetic flux density and penetrability of PMF are significantly higher than those of HMF,due to its faster variation in transient current and higher peak value of magnetic flux density.In addition,PMF drives a stronger Lorentz force and deeper penetration depth than HMF does,because HMF creates higher eddy current and reverse electromagnetic field which weakens the original electromagnetic field.The microstructure of a billet by HMF is composed of columnar structure regions and central fine grain regions.By contrast,the billet by PMF has a uniform microstructure which is characterized by ultra-refined and uniform grains because PMF drives a strong dual convection,which increases the uniformity of the temperature field,enhances the impact of the liquid flow on the edge of the liquid pool and reduces the curvature radius of liquid pool.Eventually,PMF shows a good prospect for industrialization.
基金supported by the Major State Basic Research and Development Project of China (No.2005CB623707)the Innovative Research Team Project of Northeastern University (No.N090109001)
文摘To improve the quality of 7050 aluminum alloy ingots, low-frequency electromagnetic （LFE） field was applied during the conventional hot-top casting process. Macrostructures and microstructures of the ingots by the conventional and LFE hot-top casting processes were studied. The experimental results show that when the LFE field is turn off during the hot-top casting process, cold folding appears, and the as-cast structure becomes very coarse. Additionally, the thickness of the shell zone is much thinner during the low-frequency electromagnetic hot-top casting process than that during the conventional hot-top casting process. Some reasons for low-frequency electromagnetic field improving the surface quality, refining the structure of the ingot, and minimizing the thickness of the shell zone have been studied.
基金financially supported by the National Key Research and Development Program of China(Grant No.2021YFB3701004)the National Natural Science Foundation of China(Grant Nos.51971054 and 52171055)the Fundamental Research Funds for the Central Universities(N2009006 and N2107007)。
文摘Due to lattice reorientation,grain segmentation,induced recrystallization,twins play a very important role in regulating texture,refining grains,improving mechanical properties and corrosion resistance,and has received more extensive attention.Numerous studies have shown that{10-12}<10-11>tensile twins(TTWs)are easily activated in large quantities due to the lower critical resolve shear stresses(CRSS).Introduction of TTWs under uniaxial compression improved the strength,ductility,and formability of magnesium(Mg)alloys.Moreover,TTWs produced by multi-directional impact forging(MDIF)can optimize the microstructure by dividing grains and promoting recrystallization,resulting in significant improvement of mechanical properties.Although{10-11}<10-12>compressive twins(CTWs)and{10-11}-{10-12}double twins(DTWs)can promote dynamic recrystallization(DRX),they are also favorable nucleation sites for cracks.In addition,the type and volume fraction of twins can affect the corrosion resistance,and they also play different roles in the corrosion process of different Mg alloys.Twins have shown great potential for improving structure and properties,but a comprehensive and critical discussion of twins in Mg alloys is still lacking.Therefore,based on previous studies,this article reviews the common types and variants of twins in Mg alloys,influencing factors,and their effects on the microstructure,mechanical properties and corrosion resistance.In addition,some interesting ideas are being proposed for further research.
基金the National Basic Research Program of China(2013CB632203)Liaoning Provincial Natural Science Foundation(Grant No.2014028027)。
文摘Four Mg–Gd–Y–Nd–Zr alloys were prepared by mold casting to investigate the effects of Nd/Gd ratios on microstructures and mechanical properties.The as-cast alloys mainly consist ofα-Mg andβ-Mg5(GdYNd).Volume fractions of the second phase increase and grains were slightly refined with the rising Nd/Gd ratio,when the alloying addition is equal.Meanwhile,fibers of second phase also increase in the extruded alloys when the Nd/Gd value increases.However,the Nd/Gd ratio could hardly influence the mechanical properties of the extruded alloys.The aging hardening response of the extruded alloy differs due to different Nd/Gd ratios.The potential mechanisms have also been discussed in detail.
基金This work was supported by the National Key Re-search and Development Program of China(Grant No.2016YFB0301101)the National Natural Science Foundation of China(Grant No.51971054)the Fundamental Research Funds for the Central Universities(Grant No.N180904006 and N2009006).
文摘For obtaining the finer grains of magnesium alloy,a novel combined pulsed magnetic field with different initial phases,also called out-ofphase pulsed magnetic field(OPPMF),was applied to study the solidification structure of AZ80 magnesium alloy.The numerical simulation was simultaneously conducted to investigate the refinement mechanisms.The experimental results showed that the macrostructure could be effectively refined by applying external magnetic field.Meanwhile,finer grains were obtained with the higher current intensity.However,the increase of current intensity could only refine the grains to about 0.5 mm.Furthermore,compared to a single pulsed magnetic field(PMF)and alternating series of OPPMF(Connection II),a finer structure was observed when the consecutive series of OPPMF(Connection I)was imposed.In contrast with a single PMF and Connection II,the numerical results showed that the greater axial Lorentz force was obtained under the Connection I,generating the stronger forced flow in the melt.It is believed that abundant nuclei could detach from the mold wall and move faster into the interior melt due to the stronger forced flow;besides,the lower superheat and greater temperature uniformity in bulk melt were realized,accounting for the finest structures under the Connection I.
基金Funded by the National Key Technology R&D Program of China(No.2007BAE38B01)
文摘The mechanical properties and microstructures of 6013 alloy after different thermomechanical treatments were investigated. The detailed dislocation configurations after deformation and morphologies of age hardening precipitates were examined through transmission electron microscopy （TEM）. The experimental results show that the thermomechanical treatment can significantly enhance the strength of 6013 alloy, and has a similar influence trend on single and two-step aging behaviors. With the increasing deformation ratio, the peak-hardness （HVmax） increases, the time to HV shortens, and the density of tangled dislocation network increases. The aging precipitates become larger and inhomogeneous by applying thernomechanical treatment.
文摘The Mg-xGd-2.6Nd-0.5Zn-0.5Zr(x=0,3.0,4.5 and 6.0,wt.%)alloys were prepared by gravity casting and then T6 treatment.Microstructures of the alloy were observed using optical microscopy and scanning electron microscopy.Results show that the as-cast alloys contained network Mg3Gd phases,blocky and needle-like Mg12(Nd,Gd)phases.The a(Zr)particle inclusions in the a(Mg)matrix are also observed.Content of the secondary phases decreases as Gd content increases.Tensile test results show that the tensile and yield strengths of all the alloys increase as Gd content increases under the as-cast and T6 conditions,but the elongation exhibits the opposite trend.The blocky Mg12(Nd,Gd)phases appear and act as crack initiator and deteriorates the experimental alloys’ductility with the increase of Gd content,especially as Gd content increases to 6.0 wt.%,so the Mg-6.0Gd-2.6Nd-0.5Zn-0.5Zr alloy has the lowest elongation value compared to the other alloys studied.After T6 treatment,the Mg-4.5Gd-2.6Nd-0.5Zn-0.5Zr alloy exhibits the optimal mechanical properties both at room temperature and 250℃.
基金the financial supports from the National Natural Science Foundation of China (51674078, 51374067)
文摘The ingot was prepared by direct-chill(DC)casting technology with different casting speeds under the influence of intensive melt shearing to explore the effect of casting speed and intensive melt shearing on the floating grains and negative centerline segregation.The results indicate that the application of intensive melt shearing in DC casting process can distribute the floating grains uniformly,reduce the area fraction of the floating grains,alleviate the negative centerline segregation,and improve the uniformity of temperature field in the sump.It is also suggested that under the influence of intensive melt shearing,the casting speed plays a crucial role in the amounts and distribution of floating grains.At low casting speed,the intensive melt shearing can significantly reduce the area fraction of the floating grains and distribute them uniformly throughout the ingot.However,this effect gradually disappears with the increase of casting speed.
基金financially supported by the National Natural Science Foundation of China(Grant No.51974082)the Programme of Introducing Talents of Discipline Innovation to Universities 2.0(the 111 Project of China 2.0,No.BP0719037)
文摘In this work,the discharge properties and electrochemical behaviors of as-cast AZ80-La-Gd anode for Mg-air battery have been investigated and compared with the AZ80 anode.The microstructure evolution,electrochemical behaviors and surface morphologies after discharge have been discussed to connect the discharge properties.The results indicate that the modified AZ80-La-Gd is an outstanding candidate for anode for Mg-air batter,which has high cell voltage,stable discharge curves,good specific capacity and energy,and good anodic efficiency.It exhibits the best anodic efficiency,specific capacity and energy of 76.45%,1703.6 mAh·g^(-1)and 2186.3 mWh·g^(-1),respectively,which are20.24%,18.92%and 25.71%higher than values for AZ80 anode.Such excellent discharge performance is attributed to the Al-RE particles.They refine the Mg_(17)Al_(12)phase and therefore improve the self-corrosion resistance and desorption ability of AZ80 anode.
基金financially supported by the National Basic Research Program of China(Grant No.:2012CB723307-03)the Fundamental Research Funds for the Central Universities(Grant No.:N130409003)the National Natural Science Foundation of China(Grant No.:51204046)of China
文摘Large and segregated primary Si particles may drastically decrease the mechanical properties of AI-Si alloys. To solve this problem, a P-Cr complex modifier was added into the alloy, and the effects of P-Cr complex modification and solidification conditions on the microstructure of hypereutectic Al-Si alloys casting produced in wedge-shaped copper mould were studied. The thermal analysis technique was applied to calculate the cooling rate during solidification. The microstructures were observed by means of optical and scanning electron microscopies. Results showed that the primary Si segregates in the as-cast hypereutectic AI-Si alloys. The segregation of primary Si can be inhibited by adding a P＋Cr complex modifier and increasing the cooling rate during solidification. The refinement of primary Si particles by P＋Cr complex modification is due to the formation of CrSi2 and AlP particles which act as the heterogeneous nuclei for the primary Si phase. The segregation of Si was also inhibited through the adherence of heavier CrSi2 particles to the primary Si particles.
基金This research was financially supported by National Basic Research Program of China(Grant No.2013CB632203)the Liaoning Provincial Natural Science Foundation of China(Grant No.201202072)+1 种基金National Key Technology R&D Program of China(2012BAF09B01)the Fundamental Research Foundation of Central Universities(Grant Nos.N120509002 and N120309003).
文摘Mg-9Gd-3Y-1.5Zn-0.8Zr alloys own high strength,good heat and corrosion resistance.However,it is difficult for the fabrication of large-scale billets,due to the poor deformation ability and strong hot-crack tendency.This work investigated the casting process on the microstructures and flow stress behaviors of the semi-continuous casting billets for the fabrication of large-scale Mg-9Gd-3Y-1.5Zn-0.8Zr billets.The casting process(electromagnetic intensity and casting speed)shows outstanding effects on the microstructures and flow stress behavior of the billets.The billets with the specific casting process(I=68 A,V=65 mm/min)exhibit uniform microstructures and good deformation uniformity.
基金Funded by the National Key Research and Development Program of China(No.2016YFB0301101)the Liaoning Provincial Natural Science Foundation of China(No.2014028027)the National Basic Research Program of China(No.2013CB632203)
文摘Three as-cast and as-extruded Mg-5Zn-x Y-0.6Zr(x=5 wt%, 8 wt%, 11 wt%) alloys were prepared, and the effects of Y content on the microstructures and mechanical properties of the alloys were investigated. The results show that the investigated Mg-Zn-Y-Zr alloys mainly consist of a-Mg, X-Mg12 YZn and minor amount of W-Mg_3Y_2Zn_3 phases. The volume fraction of X-Mg_(12) YZn phase increases and that of W-Mg_3Y_2Zn_3 phase decreases with the rising of Y content in the alloys. The as-extruded Mg-5Zn-11Y-0.6Zr alloy owns the optimal ultimate tensile strength and yield strength of 429 and 351 MPa, respectively. Mg-5Zn-5Y-0.6Zr alloy owns the maximum elongation of 13.6%.
