The phase constituent evolution of Mg-Zn-Y-Zr alloys with the mole ratio of Y to Zn both in the as-cast and as-annealed states at the Mg-rich corner was investigated by XRD and SEM/EDS analysis and was further explain...The phase constituent evolution of Mg-Zn-Y-Zr alloys with the mole ratio of Y to Zn both in the as-cast and as-annealed states at the Mg-rich corner was investigated by XRD and SEM/EDS analysis and was further explained from the ternary phase diagram calculation. The results show that the formation of the secondary phases in Mg-Zn-Y-Zr alloys firmly depends on the mole ratio of Y to Zn, and X （Mg 12 YZn）-phase, W （Mg 3 Y 2 Zn 3 ）-phase and I （Mg 3 YZn 6 ）-phase come out in sequence as the ratio of Y to Zn decreases. The mole ratios of Y to Zn with the corresponding phase constituent are suggested quantitatively as follows： the phase constituent is α-Mg ＋ I when the mole ratio of Y to Zn is about 0.164; α-Mg ＋ I ＋W when the mole ratio of Y to Zn is in the range of 0.164 0.33;α-Mg ＋W when the mole ratio of Y to Zn is about 0.33; α-Mg ＋W＋X when the mole ratio of Y to Zn is in the range of 0.33 1.32; and α-Mg ＋X when the mole ratio of Y to Zn is about 1.32. The results also offer a guideline for alloy selection and alloy design in Mg-Zn-Y-Zr system.展开更多
Pouring and mold temperatures are two important parameters during casting magnesium components. The present study examined their influence on hot tearing susceptibility （HTS） of commercial AZ91D and newly developed ...Pouring and mold temperatures are two important parameters during casting magnesium components. The present study examined their influence on hot tearing susceptibility （HTS） of commercial AZ91D and newly developed Mg-3Nd-0.2Zn-Zr （mass fraction, %; NZ30K） magnesium alloys in gravity permanent mold casting condition. The results indicate that mold temperature shows much more significant influence on the HTS of both alloys than pouring temperature whose influence only can be distinguished at low mold temperature （341 K for AZ91D alloy and 423 K for NZ30K alloy）. Hot tearing susceptibility prediction model concerning feeding parameters, grain size and solidification range, is more suitable to estimate the HTS of different magnesium alloys than the model only concerning feeding parameters. In order to achieve better hot tearing resistance, the ranges of pouring and mold temperatures are suggested to be 961-991 K and≥641 K for AZ91D alloy, 1003-1033 K and≥623 K for NZ30K alloy, respectively.展开更多
The microstructure and mechanical properties of the Mg-6Zn-xEr alloys in the as-cast, as-extruded and extruded-T5 states were investigated. It is found that the addition of Er has an obvious effect on improving mechan...The microstructure and mechanical properties of the Mg-6Zn-xEr alloys in the as-cast, as-extruded and extruded-T5 states were investigated. It is found that the addition of Er has an obvious effect on improving mechanical properties of Mg-6Zn based alloys. The results suggest that the Mg-6Zn-0.5Er alloy in the peak aged state shows the best tensile strength. The ultimate tensile strength and the yield tensile strength of the peak-aged Mg-6Zn-0.5Er alloy are about 329 MPa and 183 MPa, respectively, companying with a good elongation of 12%. The addition of 0.5% Er into the Mg-6Zn based alloys has a great effect on improving ageing hardening response. The highest tensile strength of the peak-aged Mg-6Zn-0.5Er alloy is mainly due to the refinement of microstructure and the precipitation of β1 phase.展开更多
Long period stacking ordered（LPSO） structure phases were prepared by conventional solidification method in Mg（94）Zn3YxGd（3-x）（x=3,2,1.5,1,mole fraction） alloys,the microstructures,corrosion and compressive mec...Long period stacking ordered（LPSO） structure phases were prepared by conventional solidification method in Mg（94）Zn3YxGd（3-x）（x=3,2,1.5,1,mole fraction） alloys,the microstructures,corrosion and compressive mechanical properties of which were investigated,separately.The results reveal that the microstructures of the as-cast Mg（94）Zn3YxGd（3-x） alloys,with n（Zn）/n（Y＋Gd）=1：1,consist of α（Mg） phase,Mg3Zn3RE2（W） phase,Mg（12）ZnRE（14H-LPSO） phase and a few bright cube-shaped Mg-Y-Gd phases.The formation and the distribution of LPSO-phase in the alloys can be influenced by the content of Gd.The volume fraction of 14H-LPSO phase increases first and then decreases with the increase of the Gd content.For the electrochemical impedance spectroscopy（EIS） measurement,a R（Q（R（QR））） model was used to fit the test results in 3.5%（mass fraction） NaCl solution at room temperature.The corrosion current densities of all samples are about 10-（-5） A/cm-2.When x（Gd）≤1%,Mg-Zn-Y-（Gd）alloy shows good corrosion resistance,which is better than that of the commercial AZ91 D magnesium alloy.The corrosion rate increases when the Gd content is higher than 1.5%.At room temperature,the compressive properties of Mg-Zn-Y-（Gd） alloys increase remarkably with the increase of the volume fraction of LPSO phase.In addition,the pinning effect of W-phase and dispersive cube-shaped Mg-Y-Gd phase is beneficial to improving the mechanical properties of as-cast Mg（94）Zn3YxGd（3-x） alloy in deformation process.展开更多
The effects of Ce, Y and Gd additions on the as-cast microstructure and mechanical properties of Mg-3Sn-2Sr alloy were investigated and compared by scanning electron microscopy, X-ray diffraction, differential scannin...The effects of Ce, Y and Gd additions on the as-cast microstructure and mechanical properties of Mg-3Sn-2Sr alloy were investigated and compared by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry analysis, tensile and creep tests. The results indicate that the Mg-3Sn-2Sr ternary alloy is mainly composed ofα-Mg, primary and eutectic SrMgSn, and Mg2Sn phases. After the additions of 1.0%Ce, 1.0%Y and 1.0%Gd to the Mg-3Sn-2Sr alloy, the Mg12Ce, YMgSn, GdMgSn and/or Mg17Sr2 phases are formed, respectively. At the same time, the formation of the primary SrMgSn phase is suppressed and the coarse needle-like primary SrMgSn phase is modified and refined. In addition, the additions of 1.0% Ce, 1.0% Y and 1.0% Gd to the Mg-3Sn-2Sr alloy can simultaneously improve the tensile and creep properties of the alloy. Among the Ce-, Y-and Gd-containing alloys, the tensile properties of the Ce-containing alloy are relatively higher than those of the Y-and Gd-containing alloys.展开更多
The microstructures and phase compositions of the as-cast and die-cast Mg-6.02Al-1.03 Sm, Mg-6.05Al-0.98Sm-0.56 Bi and Mg-5.95Al-1.01Sm-0.57 Zn alloys were investigated. Meanwhile, the tensile mechanical and flow prop...The microstructures and phase compositions of the as-cast and die-cast Mg-6.02Al-1.03 Sm, Mg-6.05Al-0.98Sm-0.56 Bi and Mg-5.95Al-1.01Sm-0.57 Zn alloys were investigated. Meanwhile, the tensile mechanical and flow properties were tested. The results show that the as-cast microstructure of Mg-6.02Al-1.03 Sm alloy is composed of δ-Mg matrix, discontinuous δ-Mg17Al12 phase and small block Al2 Sm phase with high thermal stability. Rod Mg3Bi2 phase precipitates when Bi is added, while the added metal Zn dissolves into δ-Mg matrix and δ-Mg17Al12 phase. The as-cast alloys exhibit the excellent tensile mechanical property. The tensile strength（δb） and elongation（δ） can reach 205-235 MPa and 8.5%-16.0% at ambient temperature, respectively. Meanwhile, they can also exceed 160 MPa and 14.0% at 423 K, respectively. The die-cast microstructures are refined obviously, and meanwhile the broken second phases distribute dispersedly. The die-cast alloys exhibit better tensile mechanical properties with the values of δb and δ of 240-285 MPa and 8.5%-16.5% at ambient temperature, respectively, and excellent flow property with the flow length of 1870-2420 mm. The die-cast tensile fractures at ambient temperature exhibit a typical character of ductile fracture.展开更多
The effects of the addition of 0.6%Ca（mass fraction） on the as-cast microstructure and mechanical properties of the Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc magnesium alloys were investigated and compared by optical...The effects of the addition of 0.6%Ca（mass fraction） on the as-cast microstructure and mechanical properties of the Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc magnesium alloys were investigated and compared by optical microscopy and scanning electron microscopy,differential scanning calorimetry analysis,and tensile and creep tests.The results indicate that the addition of 0.6%Ca to the Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc alloys can refine the grains of the two alloys.At the same time,the addition of 0.6%Ca to the Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc alloys can effectively improve the tensile properties of the two alloys.In addition,the addition of 0.6%Ca can also improve the creep properties of the Mg-3Ce-1.2Mn-0.9Sc alloy but is not beneficial to the creep properties of the Mg-4Y-1.2Mn-0.9Sc alloy.The different effects of minor Ca on the creep properties of the Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc alloys are possibly related to the difference in the solid solubilities of Ce and Y in Mg.展开更多
The as-extruded Mg？Sn？Ca alloys were prepared and investigated for orthopedic applications via using optical microscopy, scanning electron microscopy, X-ray diffraction, as well as tensile, immersion and electrochem...The as-extruded Mg？Sn？Ca alloys were prepared and investigated for orthopedic applications via using optical microscopy, scanning electron microscopy, X-ray diffraction, as well as tensile, immersion and electrochemical tests. The results showed that, with the addition of 1% Sn and the Ca content of 0.2%？0.5%, the microstructure of the as-extruded Mg？Sn？Ca alloys became homogenous, which led to increased mechanical properties and improved corrosion resistance. Further increase of Ca content up to 1.5% improved the strength, but deteriorated the ductility and corrosion resistance. For the alloy containing 0.5% Ca, when the Sn content increased from 1% to 3%, the ultimate tensile strength increased with a decreased corrosion resistance, and the lowest yield strength and ductility appeared with the Sn content of 2%. These behaviors were determined by Sn/Ca mass ratio. The analyses showed that as-extruded Mg？1Sn？0.5Ca alloy was promising as a biodegradable orthopedic implant.展开更多
Accumulative roll-bonding （ARB） was applied to Mg-Al-Zn magnesium alloy sheets to prepare ultrafine-grain microstructure. Significant grain refinement is achieved after three cycles of ARB with average grain size of...Accumulative roll-bonding （ARB） was applied to Mg-Al-Zn magnesium alloy sheets to prepare ultrafine-grain microstructure. Significant grain refinement is achieved after three cycles of ARB with average grain size of about 1.3 μm. The microstructure is characterized by nearly uniform ultrafine equiaxed microstructure without twins. The evolution of the misorientation distribution during ARB was measured by EBSD. Grain refinement can be contributed to the grain subdivision induced by severe accumulated strain, the accumulated strain enhanced concurrent dynamic recovery and recrystallization as well as the complicated distribution of interface and shear strain during ARB.展开更多
The microstructure, mechanical properties and fracture behavior of sand-cast Mg-10Gd-3Y-0.5Zr alloy （mass fraction,%） under T6 condition （air cooling after solid solution and then aging heat treatment） were invest...The microstructure, mechanical properties and fracture behavior of sand-cast Mg-10Gd-3Y-0.5Zr alloy （mass fraction,%） under T6 condition （air cooling after solid solution and then aging heat treatment） were investigated. The optimum T6 heat treatments for sand-cast Mg-10Gd-3Y-0.5Zr alloy are （525 ℃, 12 h＋225 ℃, 14 h） and （525 ℃, 12 h＋250 ℃, 12 h） according to age hardening curve and mechanical properties, respectively. The ultimate tensile strength, yield strength and elongation of the Mg-10Gd-3Y-0.5Zr alloy treated by the two optimum T6 processes are 339.9 MPa, 251.6 MPa, 1.5%and 359.6 MPa, 247.3 MPa, 2.7%, respectively. The tensile fracture mode of peak-aged Mg-10Gd-3Y-0.5Zr alloy is transgranular quasi-cleavage fracture.展开更多
The corrosion behaviours of Mg-5Y-7Gd-1Nd-0.5Zr magnesium alloys prepared by as-casting and extrusion were investigated in 5% NaCl aqueous solution by immersion and electrochemical tests. The microstructure indicates ...The corrosion behaviours of Mg-5Y-7Gd-1Nd-0.5Zr magnesium alloys prepared by as-casting and extrusion were investigated in 5% NaCl aqueous solution by immersion and electrochemical tests. The microstructure indicates the mean grain size of 15 μm for the extruded and 100 μm for the as-cast Mg-5Y-7Gd-1Nd-0.5Zr magnesium alloys. The corrosion morphology of as-cast sample shows pitting corrosion and little filiform corrosion, but that of the extruded sample shows pitting corrosion at the initial stage. The corrosion rate of extruded sample is higher than that of as-cast Mg-5Y-7Gd-1Nd-0.5Zr alloy according to the immersion test. The second phases containing RE acting as cathodes improve the corrosion properties. The corrosion potentials of as-cast and extruded Mg-5Y-7Gd-1Nd-0.5Zr alloys are -1.658 V and -1.591 V, respectively. The origins of the distinctive corrosion behavior of as-cast and extruded Mg-5Y-7Gd-1Nd-0.5Zr Mg alloys were discussed.展开更多
Microstructure evolution and texture development and their effects on mechanical properties of a Mg-Gd-Y-Zr alloy during equal channel angular pressing（ECAP） were investigated.It is found that the microstructure is ...Microstructure evolution and texture development and their effects on mechanical properties of a Mg-Gd-Y-Zr alloy during equal channel angular pressing（ECAP） were investigated.It is found that the microstructure is still inhomogeneous after four passes,and two zones,namely the fine grain zone（FGZ） and the coarse grain zone（CGZ） are formed.The grain refinement occurs mainly by particle-stimulated nucleation（PSN） mechanism,which led to a more random texture after four passes of ECAP.In the ECAP-processed alloy,the strength did not increase while the ductility was enhanced dramatically compared with the as-received condition.The change of ductility of this alloy was discussed in terms of texture and second phase particles.展开更多
Mg-Gd-Y-Zr alloys were purified by filtering purification with and without vacuum. The type, morphology, size distribution and volume fraction of inclusion were analyzed with OM and SEM. The effect of inclusion in Mg-...Mg-Gd-Y-Zr alloys were purified by filtering purification with and without vacuum. The type, morphology, size distribution and volume fraction of inclusion were analyzed with OM and SEM. The effect of inclusion in Mg-Gd-Y-Zr alloys on anticorrosion ability was investigated with salt spray test and electrochemical test. The results show that the inclusions in the alloy can be removed effectively by filtering purification. The average size of inclusions in the alloys is decreased from 12.7 μm to 2.0 μm and the volume fraction of inclusions is reduced from 0.30% to 0.04%. With the decrease of the size of inclusions in the alloys, the corrosion rate of the alloys decreases dramatically from 38.8 g/（m 2 ·d） to 2.4 g/（m 2 ·d） in the salt spray test. The corrosion potential increases while the corrosion current decreases and the polarization resistance increases in the electrochemical tests, which indicates that the anticorrosion ability is improved.展开更多
The morphology and orientation of the growth twins formed in the cast Mg-Zn-Cu-Zr alloys aged at 100 ＆#176;C were characterized using optical microscopy and transmission electron microscopy. It was found that twins w...The morphology and orientation of the growth twins formed in the cast Mg-Zn-Cu-Zr alloys aged at 100 ＆#176;C were characterized using optical microscopy and transmission electron microscopy. It was found that twins were invisible in the as-cast or solutionized Mg-Zn-Cu-Zr alloys while {10 12} twins were exclusively formed in the aged condition. The twinning behavior was significantly affected by two factors, namely, the Zn content and the heat treatment process. A possible formation mechanism of such growth twins was discussed using the viewpoint of vacancy.展开更多
The as-cast microstructures and mechanical properties of Mg?4Zn?xY?1Ca (x=1.0, 1.5, 2.0 and 3.0, mass fraction, %) alloys were investigated and compared. The results indicate that all the as-cast alloys are mainly com...The as-cast microstructures and mechanical properties of Mg?4Zn?xY?1Ca (x=1.0, 1.5, 2.0 and 3.0, mass fraction, %) alloys were investigated and compared. The results indicate that all the as-cast alloys are mainly composed ofα-Mg, Mg2Ca, Ca2Mg6Zn3,I (Mg3YZn6) andW (Mg3Y2Zn3) phases. However, with Y content increasing from 0.86% to 2.68%, the amount of the Ca2Mg6Zn3 phase gradually decreases but that of theI (Mg3YZn6) andW (Mg3Y2Zn3) phases gradually increases. Furthermore, an increase in Y content from 0.86% to 2.68% also causes the grain size of the as-cast alloys to gradually decrease. In addition, the tensile and creep properties of the as-cast alloys vary with Y content. Namely, with Y content increasing from 0.86% to 2.68%, the creep properties gradually increase, whereas the tensile properties firstly increase and attain the maximum at 1.77% Y, beyond that they decrease. Amongst the as-cast alloys with 0.86% Y, 1.19% Y, 1.77% Y and 2.68% Y, the alloy with 1.77% Y exhibits the relatively optimal tensile and creep properties.展开更多
基金Project(50725413)supported by the National Natural Science Foundation of China
文摘The phase constituent evolution of Mg-Zn-Y-Zr alloys with the mole ratio of Y to Zn both in the as-cast and as-annealed states at the Mg-rich corner was investigated by XRD and SEM/EDS analysis and was further explained from the ternary phase diagram calculation. The results show that the formation of the secondary phases in Mg-Zn-Y-Zr alloys firmly depends on the mole ratio of Y to Zn, and X （Mg 12 YZn）-phase, W （Mg 3 Y 2 Zn 3 ）-phase and I （Mg 3 YZn 6 ）-phase come out in sequence as the ratio of Y to Zn decreases. The mole ratios of Y to Zn with the corresponding phase constituent are suggested quantitatively as follows： the phase constituent is α-Mg ＋ I when the mole ratio of Y to Zn is about 0.164; α-Mg ＋ I ＋W when the mole ratio of Y to Zn is in the range of 0.164 0.33;α-Mg ＋W when the mole ratio of Y to Zn is about 0.33; α-Mg ＋W＋X when the mole ratio of Y to Zn is in the range of 0.33 1.32; and α-Mg ＋X when the mole ratio of Y to Zn is about 1.32. The results also offer a guideline for alloy selection and alloy design in Mg-Zn-Y-Zr system.
基金Project (2009AA033501) supported by the High-tech Research and Development Program of China
文摘Pouring and mold temperatures are two important parameters during casting magnesium components. The present study examined their influence on hot tearing susceptibility （HTS） of commercial AZ91D and newly developed Mg-3Nd-0.2Zn-Zr （mass fraction, %; NZ30K） magnesium alloys in gravity permanent mold casting condition. The results indicate that mold temperature shows much more significant influence on the HTS of both alloys than pouring temperature whose influence only can be distinguished at low mold temperature （341 K for AZ91D alloy and 423 K for NZ30K alloy）. Hot tearing susceptibility prediction model concerning feeding parameters, grain size and solidification range, is more suitable to estimate the HTS of different magnesium alloys than the model only concerning feeding parameters. In order to achieve better hot tearing resistance, the ranges of pouring and mold temperatures are suggested to be 961-991 K and≥641 K for AZ91D alloy, 1003-1033 K and≥623 K for NZ30K alloy, respectively.
基金Project(51071004)supported by the National Natural Science Foundation of ChinaProject(2011BAE22B01-3)supported by the National Key Technology R&D Program during the 12th Five-Year Period,China
文摘The microstructure and mechanical properties of the Mg-6Zn-xEr alloys in the as-cast, as-extruded and extruded-T5 states were investigated. It is found that the addition of Er has an obvious effect on improving mechanical properties of Mg-6Zn based alloys. The results suggest that the Mg-6Zn-0.5Er alloy in the peak aged state shows the best tensile strength. The ultimate tensile strength and the yield tensile strength of the peak-aged Mg-6Zn-0.5Er alloy are about 329 MPa and 183 MPa, respectively, companying with a good elongation of 12%. The addition of 0.5% Er into the Mg-6Zn based alloys has a great effect on improving ageing hardening response. The highest tensile strength of the peak-aged Mg-6Zn-0.5Er alloy is mainly due to the refinement of microstructure and the precipitation of β1 phase.
基金Project(51374084)supported by the National Natural Science Foundation of ChinaProject supported by the Power Electronics Science and Education Development Program of Delta Environmental&Educational Foundation,ChinaProject(2010K10-08)supported by the Science and Technology Plan(Industrial Research)of Shaanxi Province,China
文摘Long period stacking ordered（LPSO） structure phases were prepared by conventional solidification method in Mg（94）Zn3YxGd（3-x）（x=3,2,1.5,1,mole fraction） alloys,the microstructures,corrosion and compressive mechanical properties of which were investigated,separately.The results reveal that the microstructures of the as-cast Mg（94）Zn3YxGd（3-x） alloys,with n（Zn）/n（Y＋Gd）=1：1,consist of α（Mg） phase,Mg3Zn3RE2（W） phase,Mg（12）ZnRE（14H-LPSO） phase and a few bright cube-shaped Mg-Y-Gd phases.The formation and the distribution of LPSO-phase in the alloys can be influenced by the content of Gd.The volume fraction of 14H-LPSO phase increases first and then decreases with the increase of the Gd content.For the electrochemical impedance spectroscopy（EIS） measurement,a R（Q（R（QR））） model was used to fit the test results in 3.5%（mass fraction） NaCl solution at room temperature.The corrosion current densities of all samples are about 10-（-5） A/cm-2.When x（Gd）≤1%,Mg-Zn-Y-（Gd）alloy shows good corrosion resistance,which is better than that of the commercial AZ91 D magnesium alloy.The corrosion rate increases when the Gd content is higher than 1.5%.At room temperature,the compressive properties of Mg-Zn-Y-（Gd） alloys increase remarkably with the increase of the volume fraction of LPSO phase.In addition,the pinning effect of W-phase and dispersive cube-shaped Mg-Y-Gd phase is beneficial to improving the mechanical properties of as-cast Mg（94）Zn3YxGd（3-x） alloy in deformation process.
基金Project(CSTC2013jcyjC60001)supported by the Chongqing Science and Technology Commission of ChinaProject(KJ120834)supported by the Chongqing Education Commission of ChinaProject(CQUT1205)supported by the Open Funds from Key Laboratory of Manufacture and Test Techniques for Automobile Parts,Ministry of Education,Chongqing University of Technology,China
文摘The effects of Ce, Y and Gd additions on the as-cast microstructure and mechanical properties of Mg-3Sn-2Sr alloy were investigated and compared by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry analysis, tensile and creep tests. The results indicate that the Mg-3Sn-2Sr ternary alloy is mainly composed ofα-Mg, primary and eutectic SrMgSn, and Mg2Sn phases. After the additions of 1.0%Ce, 1.0%Y and 1.0%Gd to the Mg-3Sn-2Sr alloy, the Mg12Ce, YMgSn, GdMgSn and/or Mg17Sr2 phases are formed, respectively. At the same time, the formation of the primary SrMgSn phase is suppressed and the coarse needle-like primary SrMgSn phase is modified and refined. In addition, the additions of 1.0% Ce, 1.0% Y and 1.0% Gd to the Mg-3Sn-2Sr alloy can simultaneously improve the tensile and creep properties of the alloy. Among the Ce-, Y-and Gd-containing alloys, the tensile properties of the Ce-containing alloy are relatively higher than those of the Y-and Gd-containing alloys.
基金Project(2013AA031001)supported by the National High-tech Research and Development Program of ChinaProject(2011A080403008)supported by the Major Science and Technology Project of Guangdong Province,China
文摘The microstructures and phase compositions of the as-cast and die-cast Mg-6.02Al-1.03 Sm, Mg-6.05Al-0.98Sm-0.56 Bi and Mg-5.95Al-1.01Sm-0.57 Zn alloys were investigated. Meanwhile, the tensile mechanical and flow properties were tested. The results show that the as-cast microstructure of Mg-6.02Al-1.03 Sm alloy is composed of δ-Mg matrix, discontinuous δ-Mg17Al12 phase and small block Al2 Sm phase with high thermal stability. Rod Mg3Bi2 phase precipitates when Bi is added, while the added metal Zn dissolves into δ-Mg matrix and δ-Mg17Al12 phase. The as-cast alloys exhibit the excellent tensile mechanical property. The tensile strength（δb） and elongation（δ） can reach 205-235 MPa and 8.5%-16.0% at ambient temperature, respectively. Meanwhile, they can also exceed 160 MPa and 14.0% at 423 K, respectively. The die-cast microstructures are refined obviously, and meanwhile the broken second phases distribute dispersedly. The die-cast alloys exhibit better tensile mechanical properties with the values of δb and δ of 240-285 MPa and 8.5%-16.5% at ambient temperature, respectively, and excellent flow property with the flow length of 1870-2420 mm. The die-cast tensile fractures at ambient temperature exhibit a typical character of ductile fracture.
基金Projects (CSTC2013jcyjC60001) supported by the Chongqing Science and Technology Commission of ChinaProject (KJ120834) supported by the Chongqing Education Commission of ChinaProject (CQUT1205) supported by the Open Funds from Key Laboratory of Manufacture and Test Techniques for Automobile Parts(Chongqing University of Technology),Ministry of Education,China
文摘The effects of the addition of 0.6%Ca（mass fraction） on the as-cast microstructure and mechanical properties of the Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc magnesium alloys were investigated and compared by optical microscopy and scanning electron microscopy,differential scanning calorimetry analysis,and tensile and creep tests.The results indicate that the addition of 0.6%Ca to the Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc alloys can refine the grains of the two alloys.At the same time,the addition of 0.6%Ca to the Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc alloys can effectively improve the tensile properties of the two alloys.In addition,the addition of 0.6%Ca can also improve the creep properties of the Mg-3Ce-1.2Mn-0.9Sc alloy but is not beneficial to the creep properties of the Mg-4Y-1.2Mn-0.9Sc alloy.The different effects of minor Ca on the creep properties of the Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc alloys are possibly related to the difference in the solid solubilities of Ce and Y in Mg.
基金Project(2013CB632200)supported by the National Basic Research Program of ChinaProjects(51474043,51531002)supported by the National Natural Science Foundation of China+1 种基金Projects(CSTC2013JCYJC60001,KJZH14101)supported by Chongqing Municipal Government,ChinaProject(2015M581350)supported by the China Postdoctoral Science Foundation
文摘The as-extruded Mg？Sn？Ca alloys were prepared and investigated for orthopedic applications via using optical microscopy, scanning electron microscopy, X-ray diffraction, as well as tensile, immersion and electrochemical tests. The results showed that, with the addition of 1% Sn and the Ca content of 0.2%？0.5%, the microstructure of the as-extruded Mg？Sn？Ca alloys became homogenous, which led to increased mechanical properties and improved corrosion resistance. Further increase of Ca content up to 1.5% improved the strength, but deteriorated the ductility and corrosion resistance. For the alloy containing 0.5% Ca, when the Sn content increased from 1% to 3%, the ultimate tensile strength increased with a decreased corrosion resistance, and the lowest yield strength and ductility appeared with the Sn content of 2%. These behaviors were determined by Sn/Ca mass ratio. The analyses showed that as-extruded Mg？1Sn？0.5Ca alloy was promising as a biodegradable orthopedic implant.
基金Project (50801027) supported by the National Natural Science Foundation of ChinaProject(2007001) supported by the Public Foundation of Guangdong Key Laboratory for Advanced Metallic Materials Processing,South China University of Technology,China
文摘Accumulative roll-bonding （ARB） was applied to Mg-Al-Zn magnesium alloy sheets to prepare ultrafine-grain microstructure. Significant grain refinement is achieved after three cycles of ARB with average grain size of about 1.3 μm. The microstructure is characterized by nearly uniform ultrafine equiaxed microstructure without twins. The evolution of the misorientation distribution during ARB was measured by EBSD. Grain refinement can be contributed to the grain subdivision induced by severe accumulated strain, the accumulated strain enhanced concurrent dynamic recovery and recrystallization as well as the complicated distribution of interface and shear strain during ARB.
基金Project(51275295)supported by the National Natural Science Foundation of ChinaProject(USCAST2012-15)supported by the Funded Projects of SAST-SJTU Joint Research Centre of Advanced Aerospace Technology,ChinaProject(20120073120011)supported by the Research Fund for the Doctoral Program of Higher Education of China
文摘The microstructure, mechanical properties and fracture behavior of sand-cast Mg-10Gd-3Y-0.5Zr alloy （mass fraction,%） under T6 condition （air cooling after solid solution and then aging heat treatment） were investigated. The optimum T6 heat treatments for sand-cast Mg-10Gd-3Y-0.5Zr alloy are （525 ℃, 12 h＋225 ℃, 14 h） and （525 ℃, 12 h＋250 ℃, 12 h） according to age hardening curve and mechanical properties, respectively. The ultimate tensile strength, yield strength and elongation of the Mg-10Gd-3Y-0.5Zr alloy treated by the two optimum T6 processes are 339.9 MPa, 251.6 MPa, 1.5%and 359.6 MPa, 247.3 MPa, 2.7%, respectively. The tensile fracture mode of peak-aged Mg-10Gd-3Y-0.5Zr alloy is transgranular quasi-cleavage fracture.
基金Project (2011BAE22B01) supported by the National Key Technology R&D Program of China
文摘The corrosion behaviours of Mg-5Y-7Gd-1Nd-0.5Zr magnesium alloys prepared by as-casting and extrusion were investigated in 5% NaCl aqueous solution by immersion and electrochemical tests. The microstructure indicates the mean grain size of 15 μm for the extruded and 100 μm for the as-cast Mg-5Y-7Gd-1Nd-0.5Zr magnesium alloys. The corrosion morphology of as-cast sample shows pitting corrosion and little filiform corrosion, but that of the extruded sample shows pitting corrosion at the initial stage. The corrosion rate of extruded sample is higher than that of as-cast Mg-5Y-7Gd-1Nd-0.5Zr alloy according to the immersion test. The second phases containing RE acting as cathodes improve the corrosion properties. The corrosion potentials of as-cast and extruded Mg-5Y-7Gd-1Nd-0.5Zr alloys are -1.658 V and -1.591 V, respectively. The origins of the distinctive corrosion behavior of as-cast and extruded Mg-5Y-7Gd-1Nd-0.5Zr Mg alloys were discussed.
文摘Microstructure evolution and texture development and their effects on mechanical properties of a Mg-Gd-Y-Zr alloy during equal channel angular pressing（ECAP） were investigated.It is found that the microstructure is still inhomogeneous after four passes,and two zones,namely the fine grain zone（FGZ） and the coarse grain zone（CGZ） are formed.The grain refinement occurs mainly by particle-stimulated nucleation（PSN） mechanism,which led to a more random texture after four passes of ECAP.In the ECAP-processed alloy,the strength did not increase while the ductility was enhanced dramatically compared with the as-received condition.The change of ductility of this alloy was discussed in terms of texture and second phase particles.
基金Project(2007CB613700)supported by the National Basic Research Program of China
文摘Mg-Gd-Y-Zr alloys were purified by filtering purification with and without vacuum. The type, morphology, size distribution and volume fraction of inclusion were analyzed with OM and SEM. The effect of inclusion in Mg-Gd-Y-Zr alloys on anticorrosion ability was investigated with salt spray test and electrochemical test. The results show that the inclusions in the alloy can be removed effectively by filtering purification. The average size of inclusions in the alloys is decreased from 12.7 μm to 2.0 μm and the volume fraction of inclusions is reduced from 0.30% to 0.04%. With the decrease of the size of inclusions in the alloys, the corrosion rate of the alloys decreases dramatically from 38.8 g/（m 2 ·d） to 2.4 g/（m 2 ·d） in the salt spray test. The corrosion potential increases while the corrosion current decreases and the polarization resistance increases in the electrochemical tests, which indicates that the anticorrosion ability is improved.
基金Project(51201088)supported by the National Natural Science Foundation of ChinaProject(12C0324)supported by the Research Foundation of Education Bureau of Hunan Province,China+1 种基金Project(2011XQD26)supported by Doctoral Scientific Research Foundation of the University of South,ChinaProject([2011]76)supported by the Construct Program of the Key Discipline in Hunan Province,China
文摘The morphology and orientation of the growth twins formed in the cast Mg-Zn-Cu-Zr alloys aged at 100 ＆#176;C were characterized using optical microscopy and transmission electron microscopy. It was found that twins were invisible in the as-cast or solutionized Mg-Zn-Cu-Zr alloys while {10 12} twins were exclusively formed in the aged condition. The twinning behavior was significantly affected by two factors, namely, the Zn content and the heat treatment process. A possible formation mechanism of such growth twins was discussed using the viewpoint of vacancy.
基金Foundation item:Project(2007CB613704)supported by the National Basic Research Program of ChinaProject(CSTC2013jcyj C60001)supported by the Chongqing Science and Technology Commission of ChinaProject(CQUT1205)supported by the Open Funds from Key Laboratory of Manufacture and Test Techniques for Automobile Parts(Chongqing University of Technology),Ministry of Education,China
文摘The as-cast microstructures and mechanical properties of Mg?4Zn?xY?1Ca (x=1.0, 1.5, 2.0 and 3.0, mass fraction, %) alloys were investigated and compared. The results indicate that all the as-cast alloys are mainly composed ofα-Mg, Mg2Ca, Ca2Mg6Zn3,I (Mg3YZn6) andW (Mg3Y2Zn3) phases. However, with Y content increasing from 0.86% to 2.68%, the amount of the Ca2Mg6Zn3 phase gradually decreases but that of theI (Mg3YZn6) andW (Mg3Y2Zn3) phases gradually increases. Furthermore, an increase in Y content from 0.86% to 2.68% also causes the grain size of the as-cast alloys to gradually decrease. In addition, the tensile and creep properties of the as-cast alloys vary with Y content. Namely, with Y content increasing from 0.86% to 2.68%, the creep properties gradually increase, whereas the tensile properties firstly increase and attain the maximum at 1.77% Y, beyond that they decrease. Amongst the as-cast alloys with 0.86% Y, 1.19% Y, 1.77% Y and 2.68% Y, the alloy with 1.77% Y exhibits the relatively optimal tensile and creep properties.
