3D microstructures of Fe–6.5%Si(mass fraction) alloys prepared under different cooling conditions were simulated via finite element-cellular automaton(CAFE) method. The simulated results were compared to experimental...3D microstructures of Fe–6.5%Si(mass fraction) alloys prepared under different cooling conditions were simulated via finite element-cellular automaton(CAFE) method. The simulated results were compared to experimental results and found to be in accordance. Variations in the temperature field and solid-liquid region, which plays important roles in determining solidification structures, were also examined under various cooling conditions. The proposed model was utilized to determine the effects of Gaussian distribution parameters to find that the lower the mean undercooling, the higher the equiaxed crystal zone ratio; also, the larger the maximum nucleation density, the smaller the grain size. The influence of superheat on solidification structure and columnar to equiaxed transition(CET) in the cast ingot was also investigated to find that decrease in superheat from 52 K to 20 K causes the equiaxed crystal zone ratio to increase from 58.13% to 65.6%, the mean gain radius to decrease from 2.102 mm to 1.871 mm, and the CET to occur ahead of schedule. To this effect, low superheat casting is beneficial to obtain finer equiaxed gains and higher equiaxed dendrite zone ratio in Fe–6.5%Si alloy cast ingots.展开更多
PEO ceramic coatings including ZrO_2-Al_2O_3-SiO_2 in three phases were prepared on an Al-12.5%Si alloy in electrolyte solutions containing ZrO_2 nanoparticles. The microstructures and phases of the coatings were anal...PEO ceramic coatings including ZrO_2-Al_2O_3-SiO_2 in three phases were prepared on an Al-12.5%Si alloy in electrolyte solutions containing ZrO_2 nanoparticles. The microstructures and phases of the coatings were analyzed by SEM and XRD, and the heat insulation performance and the thermal shock resistance of the coatings were investigated. The compactness of the coating increased significantly and the hindrance of the Si element on plasma electrolytic oxidation process was effectively weakened. The growth rate of the coating was improved substantially with the addition of ZrO_2 nanoparticles. The PEO ceramic coatings are primarily composed of SiO_2 and high temperature steady phases such as a-Al_2O_3 and c-ZrO_2. Both the content of c-ZrO_2 and the heat-insulating property of the coating increased significantly. The ceramic coatings with special microstructure and composition formed in the solutions containing ZrO_2 nanoparticles possess excellent heat insulation performance and thermal shock resistance.展开更多
In this study, the mechanical properties of aluminum-5%magnesium doped with rare earth metal neodymium were evaluated. Fuzzy logic (FL) and artificial neural network (ANN) were used to model the mechanical properties ...In this study, the mechanical properties of aluminum-5%magnesium doped with rare earth metal neodymium were evaluated. Fuzzy logic (FL) and artificial neural network (ANN) were used to model the mechanical properties of aluminum-5%magnesium (0-0.9 wt%) neodymium. The single input (SI) to the fuzzy logic and artificial neural network models was the percentage weight of neodymium, while the multiple outputs (MO) were average grain size, ultimate tensile strength, yield strength elongation and hardness. The fuzzy logic-based model showed more accurate prediction than the artificial neutral network-based model in terms of the correlation coefficient values (R).展开更多
Aluminum alloy tubes were prepared by tube spinning.The intergranular and electrochemical corrosion tests were used to investigate the intergranular corrosion behavior of the 5A06 aluminum alloy blank sample and the s...Aluminum alloy tubes were prepared by tube spinning.The intergranular and electrochemical corrosion tests were used to investigate the intergranular corrosion behavior of the 5A06 aluminum alloy blank sample and the spinning sample.Results showed that the intergranular corrosion resistance of the spinning sample was higher than that of the blank sample.In addition,the electrochemical corrosion resistance of the spinning sample was higher than that of the blank sample.The EDS maps indicated a uniform element distribution pattern of aluminum and magnesium.Moreover,the phase composition and lattice constant of the samples were obtained by XRD analysis.The differences in microstructure between the aluminum alloy subjected to the spinning process and the untreated aluminum alloy were determined by EBSD.The differences were mainly attributed to the complex interactions among grain size,dislocations and grain boundaries.展开更多
The effects of addition of minor amount of(0.5 wt.%) antimony(Sb) or gadolinium(Gd) and combined addition of Sb and Gd(0.5 wt.%,respectively) on the hot tearing susceptibility(HTS) of Mg-5Al-3Ca alloy were investigate...The effects of addition of minor amount of(0.5 wt.%) antimony(Sb) or gadolinium(Gd) and combined addition of Sb and Gd(0.5 wt.%,respectively) on the hot tearing susceptibility(HTS) of Mg-5Al-3Ca alloy were investigated experimentally using a “T-shaped” hot tearing measuring system. Various solidification parameters of the alloys were measured and calculated through thermal analysis experiments. The microstructure, grain size, and morphology of the crack zone were characterized by scanning electron microscopy and electron backscatter diffraction, and the crystal phases of the alloys were analyzed by X-ray diffraction and energy-dispersive X-ray spectroscopy. The results showed that the addition of 0.5 wt.% Gd resulted in the increase in the vulnerable temperature range(Tv) and reduced the eutectic structure content that could participate in feeding, thereby improving the HTS of the alloy. However, addition of 0.5 wt.% Sb or combined addition of Gd and Sb(0.5 wt.%, respectively) to the Mg-5Al-3Ca alloy shortened the Tvand improved the skeleton strength of the alloy, thereby reducing HTS. Moreover, significantly refined structure of Mg-5Al-3Ca-0.5Gd-0.5Sb alloy improved the feeding ability of the eutectic structure, thus the alloy exhibited the lowest HTS.展开更多
Active soldering of 5A06 Al alloy was performed at 300 ℃ by using Sn-1Ti and Sn-1Ti-0.3Ga active solders, respectively. Theeffects of soldering time on the microstructure and mechanical properties of the joints were ...Active soldering of 5A06 Al alloy was performed at 300 ℃ by using Sn-1Ti and Sn-1Ti-0.3Ga active solders, respectively. Theeffects of soldering time on the microstructure and mechanical properties of the joints were investigated. The results showed that the Sn-1Tisolder broke the oxide film on the surface of the Al substrate and induced intergranular diffusion in the Al substrate. When Ga was added tothe solder, severe dissolution pits appeared in the Al substrate due to the action of Sn-1Ti-0.3Ga solder, and many Al particles were flakedfrom the matrix into the solder seam. Under thermal stress and the Ti adsorption effect, the oxide film cracked. With increasing solderingtime, the shear strength of 5A06 Al alloy joints soldered with Sn-1Ti and Sn-1Ti-0.3Ga active solders increased. When soldered for 90 min,the joint soldered with Sn-1Ti-0.3Ga solder had a higher shear strength of 22.12 MPa when compared to Sn-1Ti solder.展开更多
Based on Langmuir equation and thermodynamic properties of iron-silicon binary alloy, a mathematical model about the process of electron-beam evaporated binary alloy Fe-6.5%Si was established. Variation of the composi...Based on Langmuir equation and thermodynamic properties of iron-silicon binary alloy, a mathematical model about the process of electron-beam evaporated binary alloy Fe-6.5%Si was established. Variation of the composition of molten pool, vapor and deposit with time, length of transient time and the composition of molten pool, deposit under the steady condition were presented according to the numerical model. The experimental results on the composition of deposit were compared to the data calculated through the model. The results show that the model is applicable, after evaporating for about 50min, the compositions of the deposit are equal to those of the ingot.展开更多
To clarify the high temperature flow stress behavior and microstructures evolution of a V-5Cr-5Ti (mass fraction, %) alloy, the isothermal hot compression tests were conducted in the temperature range of 1423-1573 K...To clarify the high temperature flow stress behavior and microstructures evolution of a V-5Cr-5Ti (mass fraction, %) alloy, the isothermal hot compression tests were conducted in the temperature range of 1423-1573 K with strain rates of 0.01, 0.1, and 1 s-1. The results show that the measured flow stress should be revised by friction and the calculated values of friction coefficient m are in the range of 0.45-0.56. Arrhenius-type constitutive equation was developed by regression analysis. The comparison between the experimental and predicted flow stress shows that the R~ and the average absolute relative error (AARE) are 0.948 and 5.44%, respectively. The measured apparent activation energy Qa is in the range of 540-890 kJ/mol. Both dis-continuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) mechanisms are observed in the deformed alloy, but dynamic recovery (DRV) is the dominant softening mechanism up to a true strain of 1.5.展开更多
The microstructural evolution of banded 5A90 A1-Li alloy during superplastic deformation at 475℃ with an initial strain rate of 8× 10^-4 S^-1 was studied using EBSD technique. The results showed that, before def...The microstructural evolution of banded 5A90 A1-Li alloy during superplastic deformation at 475℃ with an initial strain rate of 8× 10^-4 S^-1 was studied using EBSD technique. The results showed that, before deformation, the grain shape appeared to be banded, the most grain boundaries belonged to low-angle boundaries, and the initial sheet had a dominate of { 110}(112) brass texture. During deformation, there were grain growth, grain shape change, misorientation increasing and textural weakening. The fraction of high-angle boundaries increased rapidly once the flow stress reached the peak value. Corresponding deformation mechanism for various stages of deformation was suggested. Dislocation activity was the dominant mechanism in the first stage, then dynamic recrystallization occurred, and grain rotation was expected as an accommodation for grain boundary sliding (GBS). At large strains, GBS was the main mechanism.展开更多
Specimens of ZM5 magnesium alloy were dipped into the mixed powder of Al and Zn at (390±5) ℃ for 8 h in argon gas protective environment and subjected to surface diffusion alloying processing (SDAP). The ero...Specimens of ZM5 magnesium alloy were dipped into the mixed powder of Al and Zn at (390±5) ℃ for 8 h in argon gas protective environment and subjected to surface diffusion alloying processing (SDAP). The erosion wear behaviors of ZM5 magnesium alloy before and after SDAP were investigated in two different erosion wear environments: oil and quartz environment; tap water and quartz environment. The surfaces of erosion wear specimens exhibited cutting scratch grooves in the oil and quartz environment. Corrosive attack was weak and cutting wear mechanism was responsible for the mass loss. When the erosion wear medium was changed to tap water and quartz environment, corrosion pits and cracks were obviously observed after erosion wear test. The corrosion from tap water and the scour from quartz intensified mass losses. Compared with the untreated specimens, the application of SDAP improved the erosion wear resistance in the same environment.展开更多
La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-xFex (x=0-0.20) hydrogen storage alloys were synthesized by induction melting and subsequent annealing treatment, and phase structure and electrochemical characteristics were inves...La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-xFex (x=0-0.20) hydrogen storage alloys were synthesized by induction melting and subsequent annealing treatment, and phase structure and electrochemical characteristics were investigated. All alloys consist of a single LaNi5 phase with CaCu5 structure, and the lattice constant a and the cell volume (V) of the LaNi5 phase increase with increasing x value. The maximum discharge capacity gradually decreases from 319.0 mA?h/g (x=0) to 291.9 mA?h/g (x=0.20) with the increase in x value. The high-rate dischargeability at the discharge current density of 1200 mA/g decreases monotonically from 53.1% (x=0) to 44.2% (x=0.20). The cycling stability increases with increasing x from 0 to 0.20, which is mainly ascribed to the improvement of the pulverization resistance.展开更多
The effects of Mn and Sn on the microstructure of Al?7Si?Mg alloy modified by Sr and Al?5Ti?B were studied. The results show that the columnar dendrites structure is observed with high content of Sr, indicating a pois...The effects of Mn and Sn on the microstructure of Al?7Si?Mg alloy modified by Sr and Al?5Ti?B were studied. The results show that the columnar dendrites structure is observed with high content of Sr, indicating a poisoning effect of the Al?5Ti?B grain refinement. In addition, Sr intermetallic compounds distribute on the TiB2 particles, which agglomerate inside the eutectic Si. The mechanism responsible for such poisoning was discussed. The addition of Mn changes the morphology of iron intermetallic compounds fromβ-Al5FeSi toα-Al(Mn,Fe)Si. Increasing the amount of Mn changes the morphology ofα-Al(Mn,Fe)Si from branched shape to rod-like shape with branched distribution, and finally convertsα-Al(Mn,Fe)Si to Chinese script shape. The microstructure observed by transmission electron microscopy (TEM) shows that Mg is more likely to interact with Sn in contrast with Si under the effect of Sn. Mg2Sn compound preferentially precipitates between the Si/Si interfaces and Al/Si interfaces.展开更多
基金Project(2012AA03A505)supported by the High-Tech Research and Development Program of ChinaProject(51474023)supported by the National Natural Science Foundation of China
文摘3D microstructures of Fe–6.5%Si(mass fraction) alloys prepared under different cooling conditions were simulated via finite element-cellular automaton(CAFE) method. The simulated results were compared to experimental results and found to be in accordance. Variations in the temperature field and solid-liquid region, which plays important roles in determining solidification structures, were also examined under various cooling conditions. The proposed model was utilized to determine the effects of Gaussian distribution parameters to find that the lower the mean undercooling, the higher the equiaxed crystal zone ratio; also, the larger the maximum nucleation density, the smaller the grain size. The influence of superheat on solidification structure and columnar to equiaxed transition(CET) in the cast ingot was also investigated to find that decrease in superheat from 52 K to 20 K causes the equiaxed crystal zone ratio to increase from 58.13% to 65.6%, the mean gain radius to decrease from 2.102 mm to 1.871 mm, and the CET to occur ahead of schedule. To this effect, low superheat casting is beneficial to obtain finer equiaxed gains and higher equiaxed dendrite zone ratio in Fe–6.5%Si alloy cast ingots.
基金Funded by the National Natural Science Foundation of China(Nos.51401155 and 51771140)Key Research and Development Plan in Shaanxi(No.2018GY-111)+1 种基金Shaanxi Provincial Department of Education Industrialization Cultivation Project(No.17JF009)Yulin Science and Technology Project(No.2016-16-4)and Shaanxi Science and Technology Co-ordination Innovation Project(No.2016KTZDGY-04-01)
文摘PEO ceramic coatings including ZrO_2-Al_2O_3-SiO_2 in three phases were prepared on an Al-12.5%Si alloy in electrolyte solutions containing ZrO_2 nanoparticles. The microstructures and phases of the coatings were analyzed by SEM and XRD, and the heat insulation performance and the thermal shock resistance of the coatings were investigated. The compactness of the coating increased significantly and the hindrance of the Si element on plasma electrolytic oxidation process was effectively weakened. The growth rate of the coating was improved substantially with the addition of ZrO_2 nanoparticles. The PEO ceramic coatings are primarily composed of SiO_2 and high temperature steady phases such as a-Al_2O_3 and c-ZrO_2. Both the content of c-ZrO_2 and the heat-insulating property of the coating increased significantly. The ceramic coatings with special microstructure and composition formed in the solutions containing ZrO_2 nanoparticles possess excellent heat insulation performance and thermal shock resistance.
文摘In this study, the mechanical properties of aluminum-5%magnesium doped with rare earth metal neodymium were evaluated. Fuzzy logic (FL) and artificial neural network (ANN) were used to model the mechanical properties of aluminum-5%magnesium (0-0.9 wt%) neodymium. The single input (SI) to the fuzzy logic and artificial neural network models was the percentage weight of neodymium, while the multiple outputs (MO) were average grain size, ultimate tensile strength, yield strength elongation and hardness. The fuzzy logic-based model showed more accurate prediction than the artificial neutral network-based model in terms of the correlation coefficient values (R).
基金Funded by the National Natural Science Foundation of China(No.51802189)the Shanghai Lingang Innovation Program(No.SH-LG-GK-2020-28)。
文摘Aluminum alloy tubes were prepared by tube spinning.The intergranular and electrochemical corrosion tests were used to investigate the intergranular corrosion behavior of the 5A06 aluminum alloy blank sample and the spinning sample.Results showed that the intergranular corrosion resistance of the spinning sample was higher than that of the blank sample.In addition,the electrochemical corrosion resistance of the spinning sample was higher than that of the blank sample.The EDS maps indicated a uniform element distribution pattern of aluminum and magnesium.Moreover,the phase composition and lattice constant of the samples were obtained by XRD analysis.The differences in microstructure between the aluminum alloy subjected to the spinning process and the untreated aluminum alloy were determined by EBSD.The differences were mainly attributed to the complex interactions among grain size,dislocations and grain boundaries.
基金financial support from Joint Research Fund Liaoning-Shenyang National Laboratory for Materials Science (2019JH3/30100014)Liaoning Bai Qian Wan Talents Program. Liaoning Revitalization Talents Program (Nos. XLYC1807021 and 1907007)+2 种基金High Level Innovation Team of Liaoning Province(XLYC1908006)Project of Liaoning Education Department(Nos. LQGD2019002, and LJGD2020008)Liaoning Nature Fund Guidance Plan (No. 2019-ZD-0210)。
文摘The effects of addition of minor amount of(0.5 wt.%) antimony(Sb) or gadolinium(Gd) and combined addition of Sb and Gd(0.5 wt.%,respectively) on the hot tearing susceptibility(HTS) of Mg-5Al-3Ca alloy were investigated experimentally using a “T-shaped” hot tearing measuring system. Various solidification parameters of the alloys were measured and calculated through thermal analysis experiments. The microstructure, grain size, and morphology of the crack zone were characterized by scanning electron microscopy and electron backscatter diffraction, and the crystal phases of the alloys were analyzed by X-ray diffraction and energy-dispersive X-ray spectroscopy. The results showed that the addition of 0.5 wt.% Gd resulted in the increase in the vulnerable temperature range(Tv) and reduced the eutectic structure content that could participate in feeding, thereby improving the HTS of the alloy. However, addition of 0.5 wt.% Sb or combined addition of Gd and Sb(0.5 wt.%, respectively) to the Mg-5Al-3Ca alloy shortened the Tvand improved the skeleton strength of the alloy, thereby reducing HTS. Moreover, significantly refined structure of Mg-5Al-3Ca-0.5Gd-0.5Sb alloy improved the feeding ability of the eutectic structure, thus the alloy exhibited the lowest HTS.
基金the National Natural Science Foundation of China(No.52171045).
文摘Active soldering of 5A06 Al alloy was performed at 300 ℃ by using Sn-1Ti and Sn-1Ti-0.3Ga active solders, respectively. Theeffects of soldering time on the microstructure and mechanical properties of the joints were investigated. The results showed that the Sn-1Tisolder broke the oxide film on the surface of the Al substrate and induced intergranular diffusion in the Al substrate. When Ga was added tothe solder, severe dissolution pits appeared in the Al substrate due to the action of Sn-1Ti-0.3Ga solder, and many Al particles were flakedfrom the matrix into the solder seam. Under thermal stress and the Ti adsorption effect, the oxide film cracked. With increasing solderingtime, the shear strength of 5A06 Al alloy joints soldered with Sn-1Ti and Sn-1Ti-0.3Ga active solders increased. When soldered for 90 min,the joint soldered with Sn-1Ti-0.3Ga solder had a higher shear strength of 22.12 MPa when compared to Sn-1Ti solder.
文摘Based on Langmuir equation and thermodynamic properties of iron-silicon binary alloy, a mathematical model about the process of electron-beam evaporated binary alloy Fe-6.5%Si was established. Variation of the composition of molten pool, vapor and deposit with time, length of transient time and the composition of molten pool, deposit under the steady condition were presented according to the numerical model. The experimental results on the composition of deposit were compared to the data calculated through the model. The results show that the model is applicable, after evaporating for about 50min, the compositions of the deposit are equal to those of the ingot.
基金Project(11105127) supported by the National Natural Science Foundation of China
文摘To clarify the high temperature flow stress behavior and microstructures evolution of a V-5Cr-5Ti (mass fraction, %) alloy, the isothermal hot compression tests were conducted in the temperature range of 1423-1573 K with strain rates of 0.01, 0.1, and 1 s-1. The results show that the measured flow stress should be revised by friction and the calculated values of friction coefficient m are in the range of 0.45-0.56. Arrhenius-type constitutive equation was developed by regression analysis. The comparison between the experimental and predicted flow stress shows that the R~ and the average absolute relative error (AARE) are 0.948 and 5.44%, respectively. The measured apparent activation energy Qa is in the range of 540-890 kJ/mol. Both dis-continuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) mechanisms are observed in the deformed alloy, but dynamic recovery (DRV) is the dominant softening mechanism up to a true strain of 1.5.
基金Project(51205419)supported by the National Natural Science Foundation of China
文摘The microstructural evolution of banded 5A90 A1-Li alloy during superplastic deformation at 475℃ with an initial strain rate of 8× 10^-4 S^-1 was studied using EBSD technique. The results showed that, before deformation, the grain shape appeared to be banded, the most grain boundaries belonged to low-angle boundaries, and the initial sheet had a dominate of { 110}(112) brass texture. During deformation, there were grain growth, grain shape change, misorientation increasing and textural weakening. The fraction of high-angle boundaries increased rapidly once the flow stress reached the peak value. Corresponding deformation mechanism for various stages of deformation was suggested. Dislocation activity was the dominant mechanism in the first stage, then dynamic recrystallization occurred, and grain rotation was expected as an accommodation for grain boundary sliding (GBS). At large strains, GBS was the main mechanism.
基金Project (2011JY009) supported by Education Department of Shaanxi Province, China
文摘Specimens of ZM5 magnesium alloy were dipped into the mixed powder of Al and Zn at (390±5) ℃ for 8 h in argon gas protective environment and subjected to surface diffusion alloying processing (SDAP). The erosion wear behaviors of ZM5 magnesium alloy before and after SDAP were investigated in two different erosion wear environments: oil and quartz environment; tap water and quartz environment. The surfaces of erosion wear specimens exhibited cutting scratch grooves in the oil and quartz environment. Corrosive attack was weak and cutting wear mechanism was responsible for the mass loss. When the erosion wear medium was changed to tap water and quartz environment, corrosion pits and cracks were obviously observed after erosion wear test. The corrosion from tap water and the scour from quartz intensified mass losses. Compared with the untreated specimens, the application of SDAP improved the erosion wear resistance in the same environment.
基金Project (51001043) supported by the National Natural Science Foundation of ChinaProject (NCET2011) supported by Program for New Century Excellent Talents in University, China+4 种基金Project (201104390) supported by China Postdoctoral Science Special FoundationProject (20100470990) supported by China Postdoctoral Science FoundationProject (2012IRTSTHN007) supported by Program for Innovative Research Team (in Science and Technology) in the University of Henan Province, ChinaProject (2011J1003) supported by Baotou Science and Technology Project, ChinaProject (B2010-13) supported by the Doctoral Foundation of Henan Polytechnic University, China
文摘La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-xFex (x=0-0.20) hydrogen storage alloys were synthesized by induction melting and subsequent annealing treatment, and phase structure and electrochemical characteristics were investigated. All alloys consist of a single LaNi5 phase with CaCu5 structure, and the lattice constant a and the cell volume (V) of the LaNi5 phase increase with increasing x value. The maximum discharge capacity gradually decreases from 319.0 mA?h/g (x=0) to 291.9 mA?h/g (x=0.20) with the increase in x value. The high-rate dischargeability at the discharge current density of 1200 mA/g decreases monotonically from 53.1% (x=0) to 44.2% (x=0.20). The cycling stability increases with increasing x from 0 to 0.20, which is mainly ascribed to the improvement of the pulverization resistance.
文摘The effects of Mn and Sn on the microstructure of Al?7Si?Mg alloy modified by Sr and Al?5Ti?B were studied. The results show that the columnar dendrites structure is observed with high content of Sr, indicating a poisoning effect of the Al?5Ti?B grain refinement. In addition, Sr intermetallic compounds distribute on the TiB2 particles, which agglomerate inside the eutectic Si. The mechanism responsible for such poisoning was discussed. The addition of Mn changes the morphology of iron intermetallic compounds fromβ-Al5FeSi toα-Al(Mn,Fe)Si. Increasing the amount of Mn changes the morphology ofα-Al(Mn,Fe)Si from branched shape to rod-like shape with branched distribution, and finally convertsα-Al(Mn,Fe)Si to Chinese script shape. The microstructure observed by transmission electron microscopy (TEM) shows that Mg is more likely to interact with Sn in contrast with Si under the effect of Sn. Mg2Sn compound preferentially precipitates between the Si/Si interfaces and Al/Si interfaces.