Mg-1.5Zn-0.2Zr-xCe (x=0, 0.1, 0.3, 0.5, mass fraction, %) alloys were prepared by conventional semi-continuous casting. The effect of rare earth Ce on the microstructure of Mg-1.5Zn-0.2Zr-xCe alloys was studied and th...Mg-1.5Zn-0.2Zr-xCe (x=0, 0.1, 0.3, 0.5, mass fraction, %) alloys were prepared by conventional semi-continuous casting. The effect of rare earth Ce on the microstructure of Mg-1.5Zn-0.2Zr-xCe alloys was studied and the distribution of Ce was analyzed by optical microscopy (OM), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results indicate that Ce element exists in the form of Mg12Ce phase and has an obvious refining effect on the microstructure of test alloys. As the Ce content increases, the grain size reduces, the grain boundaries turn thinner, and the distribution of Mg12Ce precipitates becomes more and more dispersed. The Mg-1.5Zn-0.2Zr alloy with 0.3%Ce has the best refinement effect. From center to periphery of the ingot, the amount of granular precipitates in the grain reduces. In longitudinal section of the ingot, some relative long columnar grains appear.展开更多
The microstructures and mechanical properties of Mg-6Zn-1Mn-4Sn-1.5Nd alloy subjected to extrusion and T5 treatment were investigated using optical microscopy（OM）, X-ray diffractometer（XRD）, scanning electron micr...The microstructures and mechanical properties of Mg-6Zn-1Mn-4Sn-1.5Nd alloy subjected to extrusion and T5 treatment were investigated using optical microscopy（OM）, X-ray diffractometer（XRD）, scanning electron microscopy（SEM）, electron back scattered diffraction（EBSD）, transmission electron microscopy（TEM）, hardness tests and uniaxial tensile tests. The results showed that the as-cast alloy consisted of α（Mg）, Mn, Mg7Zn3, Mg2 Sn and Mg Sn Nd phases. Dynamic recrystallization has completed during the extrusion process and the average grain size was 7.2 μm. After T5 treatment, the strength increased obviously, the yield strength and ultimate tensile strength of as-extruded alloy were increased by 94 and 34 MPa, respectively. Microstructure characterization revealed that the improvement of strength was determined by the high number density of β′1 rods.展开更多
A Mg-6Zn-3Gd(mass fraction,%) alloy,noted as ZG63,was coated by different micro-arc oxidation(MAO) processes,and the coating structure and corrosion resistance of the alloy were studied using scanning electron microsc...A Mg-6Zn-3Gd(mass fraction,%) alloy,noted as ZG63,was coated by different micro-arc oxidation(MAO) processes,and the coating structure and corrosion resistance of the alloy were studied using scanning electron microscopy(SEM),glancing angle X-ray diffractometry(GAXRD) and various electrochemical methods.The micro-arc oxidation process consists of three stages and corresponds with different coating structures.In the initial stage,the coating thickness is linearly increased and is controlled by electrochemical polarization.In the second stage,the coating grows mainly inward and accords with parabolic regularity.In the third stage,the loose coating forms and is controlled by local arc light.The looser coating is mainly composed of MgSiO3 and the compact coating is mainly composed of MgO.From micro-arc oxidation stage to local arc light stage,the corrosion resistance of the coated alloy firstly increases and then decreases.The satisfied corrosion resistance corresponds to the coating time ranging from 6 to10 min.展开更多
In this study,uniaxial hot compression tests were carried out between 200 and 400℃ over strain rates of0.001-1 s-1 to investigate the hot deformation behavior of Mg-2 Zn-1 Al-0.2 RE alloy with coarse grains.The avera...In this study,uniaxial hot compression tests were carried out between 200 and 400℃ over strain rates of0.001-1 s-1 to investigate the hot deformation behavior of Mg-2 Zn-1 Al-0.2 RE alloy with coarse grains.The average activation energy was measured to be 174.51 kJ/mol.In addition,a constitutive relation based on the Arrhenius equation was established.Dynamic recrystallization(DRX) kinetics were studied by Avrami equation to characterize the evolution of DRX volume fraction.DRX was favored at high temperatures of 300-400℃ and low strain rates of 0.001-0.01 s-1.According to dynamic material model and Prasad’s instability criterion,a maximum power dissipation of 38% and 32% occurs at 400℃/0.001 s-1 and 400℃/0.01 s-1,respectively.According to the proce ssing map,330-400℃/0.001-0.01 s-1was determined as the optimum deformation parameter range.展开更多
The microstructure and corrosion resistance of Mg-0.5 Zn-0.2 Ca-0.2 Ce alloy with different processing conditions were investigated.The composition was detected by X-ray fluorescence(XRF),and the microstructure was an...The microstructure and corrosion resistance of Mg-0.5 Zn-0.2 Ca-0.2 Ce alloy with different processing conditions were investigated.The composition was detected by X-ray fluorescence(XRF),and the microstructure was analyzed by optical microscopy(OM)and scanning electron microscope(SEM)equipped with energy-dispersive spectroscopy(EDS).The corrosion behavior was investigated by hydrogen evolution tests,weight loss tests and electrochemical measurements.The Mg-0.5 Zn-0.2 Ca-0.2 Ce alloy has much better corrosion resistance compared with the commercial AZ31 sheet,which can be attributed to its dispersive second phases and protective corrosion products film on the alloy surface.Moreover,the as-rolled Mg-0.5 Zn-0.2 Ca-0.2 Ce alloy shows much better corrosion resistance compared with the as-extruded Mg-0.5 Zn-0.2 Ca-0.2 Ce alloy.This can be due to three aspects:The as-rolled alloy has smaller grain size;the as-rolled alloy has lower(1010)/(1120)texture intensity;the residual stress of the as-rolled alloy is eliminated during the annealing process,but large residual stress exists in the asextruded alloy produced by the extrusion process.展开更多
基金Project(2007CB613702) supported by the National Basic Research Program of ChinaProject(CSTD2006AA4012) supported by the Key Technologies R&D Program of the Chongqing Science and Technology Commission
文摘Mg-1.5Zn-0.2Zr-xCe (x=0, 0.1, 0.3, 0.5, mass fraction, %) alloys were prepared by conventional semi-continuous casting. The effect of rare earth Ce on the microstructure of Mg-1.5Zn-0.2Zr-xCe alloys was studied and the distribution of Ce was analyzed by optical microscopy (OM), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results indicate that Ce element exists in the form of Mg12Ce phase and has an obvious refining effect on the microstructure of test alloys. As the Ce content increases, the grain size reduces, the grain boundaries turn thinner, and the distribution of Mg12Ce precipitates becomes more and more dispersed. The Mg-1.5Zn-0.2Zr alloy with 0.3%Ce has the best refinement effect. From center to periphery of the ingot, the amount of granular precipitates in the grain reduces. In longitudinal section of the ingot, some relative long columnar grains appear.
基金Project(2013CB632200)supported by the National Great Theoretic Research,ChinaProject(2011BAE22B01-3)supported by the National Sci&Tech Support Program,ChinaProject(2010DFR50010)supported by the International Cooperation,Sharing Fund of Chongqing University’s Large-scale Equipment,China
文摘The microstructures and mechanical properties of Mg-6Zn-1Mn-4Sn-1.5Nd alloy subjected to extrusion and T5 treatment were investigated using optical microscopy（OM）, X-ray diffractometer（XRD）, scanning electron microscopy（SEM）, electron back scattered diffraction（EBSD）, transmission electron microscopy（TEM）, hardness tests and uniaxial tensile tests. The results showed that the as-cast alloy consisted of α（Mg）, Mn, Mg7Zn3, Mg2 Sn and Mg Sn Nd phases. Dynamic recrystallization has completed during the extrusion process and the average grain size was 7.2 μm. After T5 treatment, the strength increased obviously, the yield strength and ultimate tensile strength of as-extruded alloy were increased by 94 and 34 MPa, respectively. Microstructure characterization revealed that the improvement of strength was determined by the high number density of β′1 rods.
文摘A Mg-6Zn-3Gd(mass fraction,%) alloy,noted as ZG63,was coated by different micro-arc oxidation(MAO) processes,and the coating structure and corrosion resistance of the alloy were studied using scanning electron microscopy(SEM),glancing angle X-ray diffractometry(GAXRD) and various electrochemical methods.The micro-arc oxidation process consists of three stages and corresponds with different coating structures.In the initial stage,the coating thickness is linearly increased and is controlled by electrochemical polarization.In the second stage,the coating grows mainly inward and accords with parabolic regularity.In the third stage,the loose coating forms and is controlled by local arc light.The looser coating is mainly composed of MgSiO3 and the compact coating is mainly composed of MgO.From micro-arc oxidation stage to local arc light stage,the corrosion resistance of the coated alloy firstly increases and then decreases.The satisfied corrosion resistance corresponds to the coating time ranging from 6 to10 min.
基金the National Key Research and Development Program of China(2016YFB0301104)National Natural Science Foundation of China(51771043)。
文摘In this study,uniaxial hot compression tests were carried out between 200 and 400℃ over strain rates of0.001-1 s-1 to investigate the hot deformation behavior of Mg-2 Zn-1 Al-0.2 RE alloy with coarse grains.The average activation energy was measured to be 174.51 kJ/mol.In addition,a constitutive relation based on the Arrhenius equation was established.Dynamic recrystallization(DRX) kinetics were studied by Avrami equation to characterize the evolution of DRX volume fraction.DRX was favored at high temperatures of 300-400℃ and low strain rates of 0.001-0.01 s-1.According to dynamic material model and Prasad’s instability criterion,a maximum power dissipation of 38% and 32% occurs at 400℃/0.001 s-1 and 400℃/0.01 s-1,respectively.According to the proce ssing map,330-400℃/0.001-0.01 s-1was determined as the optimum deformation parameter range.
基金the National Natural Science Foundation of China(Nos.51671041,51701029 and 51531002)the National Key Research and Development Program of China(No.2016YFB0301100)+2 种基金the Fundamental Research Funds for the Central Universities(No.106112016CDJXZ138811)China Postdoctoral Science Foundation Funded Project(Nos.2017M620410 and 2018T110942)the Chongqing Postdoctoral Scientific Research Foundation(No.Xm2017010)。
文摘The microstructure and corrosion resistance of Mg-0.5 Zn-0.2 Ca-0.2 Ce alloy with different processing conditions were investigated.The composition was detected by X-ray fluorescence(XRF),and the microstructure was analyzed by optical microscopy(OM)and scanning electron microscope(SEM)equipped with energy-dispersive spectroscopy(EDS).The corrosion behavior was investigated by hydrogen evolution tests,weight loss tests and electrochemical measurements.The Mg-0.5 Zn-0.2 Ca-0.2 Ce alloy has much better corrosion resistance compared with the commercial AZ31 sheet,which can be attributed to its dispersive second phases and protective corrosion products film on the alloy surface.Moreover,the as-rolled Mg-0.5 Zn-0.2 Ca-0.2 Ce alloy shows much better corrosion resistance compared with the as-extruded Mg-0.5 Zn-0.2 Ca-0.2 Ce alloy.This can be due to three aspects:The as-rolled alloy has smaller grain size;the as-rolled alloy has lower(1010)/(1120)texture intensity;the residual stress of the as-rolled alloy is eliminated during the annealing process,but large residual stress exists in the asextruded alloy produced by the extrusion process.
