This work mainly deals with the segregating behaviors of Sc and the growth of unique primary Al3Sc in AlSc alloys prepared by molten salt electrolysis. The alloys contain 0.23–1.38 wt%Sc where Sc segregation is obser...This work mainly deals with the segregating behaviors of Sc and the growth of unique primary Al3Sc in AlSc alloys prepared by molten salt electrolysis. The alloys contain 0.23–1.38 wt%Sc where Sc segregation is observed. It is found that a high current density and long electrolysis time are in favor of high Sc content, and so do the high temperature and the addition level of Sc2O3. Sc content at the edge of Al based alloy(average Sc content: 0.75 wt%) can be as high as 1.09 wt%, while it is merely 0.24 wt% at the central area. The cooling rates have a strong impact on the morphology and particle size of primary Al3Sc,but a weak influence on Sc segregation. The cusped cubic and dendritic primary Al3Sc can precipitate in the prepared Al-Sc alloys. In a slightly hypereutectic Al-0.67 wt%Sc alloy, a large and cusped dendrite grows from the edge into the center. The primary and secondary dendritic arms can be as long as 600 and 250 μm, respectively. The Sc segregating behaviors in Al-Sc alloys is due to the mechanism controlled by the limited diffusion rate of Sc in liquid Al. This can involve the establishment of a near spherical discharge interface between liquid Al and the electrolyte. The Sc rich layer near Al-molten salt interface may provide the potential primary nuclei and sufficient Sc atoms for the growth of large dendritic primary Al3Sc.展开更多
The corrosion behaviors of Al-6Mg-Zr and Al-6Mg-Zr-Sc in the sulfate-reducing bacteria （SRB） solution in anaerobic environment were studied using electrochemical, microbiological, and surface analysis methods. It wa...The corrosion behaviors of Al-6Mg-Zr and Al-6Mg-Zr-Sc in the sulfate-reducing bacteria （SRB） solution in anaerobic environment were studied using electrochemical, microbiological, and surface analysis methods. It was found that the oxide film was more compact owing to the addition of Sc resulting in the open circuit potential shifting by about 100mV positively. On the other hand, it was seen that the pitting sensitivity of Al-6Mg-Zr-Sc alloy in SRB solution decreased and its microbiologically influenced corrosion resistance was improved. Pitting corrosion occurring on the surface of the two alloys under the comprehensive action of the metabolism of SRB was observed by SEM. It was obtained by EDS that the corrosion degree increased with time and corrosion was furthered by deposition of the product.展开更多
Finite-temperature ductility-brittleness and electronic structures of Al_(3)Sc,Al_(2)Sc and AlSc are studied comparatively by first-principles calculations and ab initio molecular dynamics.Results show that Al_(3)Sc a...Finite-temperature ductility-brittleness and electronic structures of Al_(3)Sc,Al_(2)Sc and AlSc are studied comparatively by first-principles calculations and ab initio molecular dynamics.Results show that Al_(3)Sc and Al_(2)Sc are brittle at both ground state and finite temperatures,while AlSc possesses a significantly superior ductility.At ground state,AlSc is ductile from Pugh's and Poisson's criteria,while it is brittle in Pettifor's model.The ductility of all Al_(3)Sc,Al_(2)Sc and AISc improves greatly with the elevated temperature.Especially,the Cauchy pressure of AlSc undergoes a transition from negative to positive.At T>600 K,AlSc is unequivocally classified as ductile from all criteria considered.In all compounds,the Al-Al bond originated from s-p and p-p orbital hybridizations,and the Al-Sc bond dominated by p-d covalent hybridization,are the first and second strongest chemical bonds,respectively.To explain the difference in mechanical properties,the mean bond strength(MBS)is introduced in this work.The weaker Al-Al bond in AlSc,leading to a smaller MBS,could be the origin of the softer elastic stiffness and superior intrinsic ductility.The longer length of the Al-Al bond in AlSc is responsible for its weaker bond strength.Furthermore,the enhanced metallicity of the Al-Al bond in AlSc would also contribute to its exceptional ductility.The longer length of the Al-Al bond in AISc is responsible for its weaker bond strength.Furthermore,the enhanced metallicity of the Al-Al bond in AlSc would also contribute to its exceptional ductility.展开更多
Al-Sc and Al-Ti semi-infinite targets were impacted by high-speed projectiles at velocities of 0.8, 1.0, 1.2 and 1.5 km/s, respectively. It is found that the Al-Sc targets demonstrate more excellent ability to resist ...Al-Sc and Al-Ti semi-infinite targets were impacted by high-speed projectiles at velocities of 0.8, 1.0, 1.2 and 1.5 km/s, respectively. It is found that the Al-Sc targets demonstrate more excellent ability to resist high-speed impact. It is concluded that different microstructures of Al-Sc and Al-Ti alloys, including different grain sizes and secondary particles precipitated in the matrix, result in their greatly different capabilities of resisting impact. Furthermore, the effect of the size range ofnanoscale A13Sc precipitate in A1-Sc alloy on the resistance of high-speed impact was investigated. In addition, computer simulations and validation of these simulations were developed which fairly accurately represented residual crater shapes/geometries. Validated computer simulations allowed representative extrapolations of impact craters well beyond the laboratory where melt and solidification occurred at the crater wall, especially for hypervelocity impact （〉5 km/s）.展开更多
Sc solute clusters with a high number density were produced in an Al-0.3 wt.%Sc alloy when aged at250℃,while fine Al_(3)Sc precipitates were predominantly formed in the same alloy aged at 300℃.The alloy strengthened...Sc solute clusters with a high number density were produced in an Al-0.3 wt.%Sc alloy when aged at250℃,while fine Al_(3)Sc precipitates were predominantly formed in the same alloy aged at 300℃.The alloy strengthened by Sc solute clusters displayed higher yield strength and simultaneously greater ductility than its counterpart strengthened by Al_(3)Sc precipitates.This clearly demonstrates a superior strengthductility synergy promoted by the Sc solute clusters in Al-Sc alloys.The effects of Al_(3)Sc precipitates and Sc solute clusters on ductility were discussed in comparison by using a micromechanics fracture model.Since the Sc clusters were stabilized at 250℃,the Al-Sc alloys strengthened by Sc solute clusters should find extensive application fields within a wide temperature range,due to their high temperature resistance.展开更多
The physicochemical properties of the system, such as density, surface tension, specific conductance and melting point were measured. The results were discussed.
The bubble's largest pressure method was employed to measure the densities and the surface tensions ofthe NaCl-KCl(equimolar)-ScCl3 system in which the contents of ScCl3 were 10%, 20%, 30% and 40%, respectively.Th...The bubble's largest pressure method was employed to measure the densities and the surface tensions ofthe NaCl-KCl(equimolar)-ScCl3 system in which the contents of ScCl3 were 10%, 20%, 30% and 40%, respectively.The results show that while temperature increases, the densities and the sufface tensions of the melts will decrease at thesame content of ScCl3; while the content of ScCl3 in the melts increases, the densities of the melts will increase and thesufface tentions of the melts will decrease at the same temperature. The least-square method was used to treat the data,and the regression functions of the densities and the surface tensions with temperature were given. It is known from theresults that the physicochemical properties of the NaCl-KCl (equimolar)-ScCl3 system can meet the requirements ofpreparation of Al-Sc alloys through the molten salt electrolysis.展开更多
The nucleation properties and stability of the ordered precipitates in Al-Sc-Er alloy were extensively studied by first-principles calculation.The calculated substitutional formation energy reveals that the dissolved ...The nucleation properties and stability of the ordered precipitates in Al-Sc-Er alloy were extensively studied by first-principles calculation.The calculated substitutional formation energy reveals that the dissolved Sc or Er in the Al matrix is very favorable to substitute the X sublattice site in L1_(2)-Al_(3)X(X=Sc/Er).The calculated solubility curve demonstrates the significant contribution of vibrational entropy to nucleation.The interface energies for Al/Al_(3)Sc,Al/Al_(3)Er and Al_(3)Sc/Al_(3)Er were calculated in the three directions of[100],[110]and[111],and we find that the interface structure in(100)plane is the most desirable,and the interface energy of Al/Al_(3)Er is the largest.Regardless of temperature and Sc/Er ratio,the L1_(2)-Al_(3)Sc_xEr_(1-x)precipitation phase mainly forms as the core-shell structure with Al3 Er as the core and Al_(3)Sc as the shell due to lower nucleation energy.The core-shell structure behaves higher stability once the particle radius is greater than 1 nm.Furthermore,the thermodynamic driving force for the segregating of Si or Zr in Al-Sc-Er alloy should accelerate the precipitation kinetics,where Si partitions occur preferentially to the Al_(3)Er and Zr partitions preferentially to the Al matrix.Overall,these theoretical results can offer solid explanations to the available experimental results.展开更多
基金financial support of the project from the Beijing Natural Science Foundation (2184110)the National Natural Science Foundation of China (Nos. 51434005, 51704020 and 51874035)the Fundamental Research Funds for Central Universities of China (No. FRF-TP-17-035A1)
文摘This work mainly deals with the segregating behaviors of Sc and the growth of unique primary Al3Sc in AlSc alloys prepared by molten salt electrolysis. The alloys contain 0.23–1.38 wt%Sc where Sc segregation is observed. It is found that a high current density and long electrolysis time are in favor of high Sc content, and so do the high temperature and the addition level of Sc2O3. Sc content at the edge of Al based alloy(average Sc content: 0.75 wt%) can be as high as 1.09 wt%, while it is merely 0.24 wt% at the central area. The cooling rates have a strong impact on the morphology and particle size of primary Al3Sc,but a weak influence on Sc segregation. The cusped cubic and dendritic primary Al3Sc can precipitate in the prepared Al-Sc alloys. In a slightly hypereutectic Al-0.67 wt%Sc alloy, a large and cusped dendrite grows from the edge into the center. The primary and secondary dendritic arms can be as long as 600 and 250 μm, respectively. The Sc segregating behaviors in Al-Sc alloys is due to the mechanism controlled by the limited diffusion rate of Sc in liquid Al. This can involve the establishment of a near spherical discharge interface between liquid Al and the electrolyte. The Sc rich layer near Al-molten salt interface may provide the potential primary nuclei and sufficient Sc atoms for the growth of large dendritic primary Al3Sc.
基金Project supported by the National Natural Science Foundation of China (50571003)
文摘The corrosion behaviors of Al-6Mg-Zr and Al-6Mg-Zr-Sc in the sulfate-reducing bacteria （SRB） solution in anaerobic environment were studied using electrochemical, microbiological, and surface analysis methods. It was found that the oxide film was more compact owing to the addition of Sc resulting in the open circuit potential shifting by about 100mV positively. On the other hand, it was seen that the pitting sensitivity of Al-6Mg-Zr-Sc alloy in SRB solution decreased and its microbiologically influenced corrosion resistance was improved. Pitting corrosion occurring on the surface of the two alloys under the comprehensive action of the metabolism of SRB was observed by SEM. It was obtained by EDS that the corrosion degree increased with time and corrosion was furthered by deposition of the product.
基金financially supported by the National Key R&D Program of China(No.2022YFB3504401)。
文摘Finite-temperature ductility-brittleness and electronic structures of Al_(3)Sc,Al_(2)Sc and AlSc are studied comparatively by first-principles calculations and ab initio molecular dynamics.Results show that Al_(3)Sc and Al_(2)Sc are brittle at both ground state and finite temperatures,while AlSc possesses a significantly superior ductility.At ground state,AlSc is ductile from Pugh's and Poisson's criteria,while it is brittle in Pettifor's model.The ductility of all Al_(3)Sc,Al_(2)Sc and AISc improves greatly with the elevated temperature.Especially,the Cauchy pressure of AlSc undergoes a transition from negative to positive.At T>600 K,AlSc is unequivocally classified as ductile from all criteria considered.In all compounds,the Al-Al bond originated from s-p and p-p orbital hybridizations,and the Al-Sc bond dominated by p-d covalent hybridization,are the first and second strongest chemical bonds,respectively.To explain the difference in mechanical properties,the mean bond strength(MBS)is introduced in this work.The weaker Al-Al bond in AlSc,leading to a smaller MBS,could be the origin of the softer elastic stiffness and superior intrinsic ductility.The longer length of the Al-Al bond in AlSc is responsible for its weaker bond strength.Furthermore,the enhanced metallicity of the Al-Al bond in AlSc would also contribute to its exceptional ductility.The longer length of the Al-Al bond in AISc is responsible for its weaker bond strength.Furthermore,the enhanced metallicity of the Al-Al bond in AlSc would also contribute to its exceptional ductility.
文摘Al-Sc and Al-Ti semi-infinite targets were impacted by high-speed projectiles at velocities of 0.8, 1.0, 1.2 and 1.5 km/s, respectively. It is found that the Al-Sc targets demonstrate more excellent ability to resist high-speed impact. It is concluded that different microstructures of Al-Sc and Al-Ti alloys, including different grain sizes and secondary particles precipitated in the matrix, result in their greatly different capabilities of resisting impact. Furthermore, the effect of the size range ofnanoscale A13Sc precipitate in A1-Sc alloy on the resistance of high-speed impact was investigated. In addition, computer simulations and validation of these simulations were developed which fairly accurately represented residual crater shapes/geometries. Validated computer simulations allowed representative extrapolations of impact craters well beyond the laboratory where melt and solidification occurred at the crater wall, especially for hypervelocity impact （〉5 km/s）.
基金financially supported by the National Natural Science Foundation of China(Nos.52071253,51621063,51625103,51722104 and 51790482)the“111 Project”of China(BP2018008)the Financial support by the International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technologies。
文摘Sc solute clusters with a high number density were produced in an Al-0.3 wt.%Sc alloy when aged at250℃,while fine Al_(3)Sc precipitates were predominantly formed in the same alloy aged at 300℃.The alloy strengthened by Sc solute clusters displayed higher yield strength and simultaneously greater ductility than its counterpart strengthened by Al_(3)Sc precipitates.This clearly demonstrates a superior strengthductility synergy promoted by the Sc solute clusters in Al-Sc alloys.The effects of Al_(3)Sc precipitates and Sc solute clusters on ductility were discussed in comparison by using a micromechanics fracture model.Since the Sc clusters were stabilized at 250℃,the Al-Sc alloys strengthened by Sc solute clusters should find extensive application fields within a wide temperature range,due to their high temperature resistance.
文摘The physicochemical properties of the system, such as density, surface tension, specific conductance and melting point were measured. The results were discussed.
文摘The bubble's largest pressure method was employed to measure the densities and the surface tensions ofthe NaCl-KCl(equimolar)-ScCl3 system in which the contents of ScCl3 were 10%, 20%, 30% and 40%, respectively.The results show that while temperature increases, the densities and the sufface tensions of the melts will decrease at thesame content of ScCl3; while the content of ScCl3 in the melts increases, the densities of the melts will increase and thesufface tentions of the melts will decrease at the same temperature. The least-square method was used to treat the data,and the regression functions of the densities and the surface tensions with temperature were given. It is known from theresults that the physicochemical properties of the NaCl-KCl (equimolar)-ScCl3 system can meet the requirements ofpreparation of Al-Sc alloys through the molten salt electrolysis.
基金Project supported by the National Key Research and Development Program of China(2018YFB1106302)the National Natural Science Foundation of China(51821001)+1 种基金the Shanghai Jiao Tong University(15X100040018)the Anhui Province Engineering Research Center of Aluminum Matrix Composites(2017WAMC002)。
文摘The nucleation properties and stability of the ordered precipitates in Al-Sc-Er alloy were extensively studied by first-principles calculation.The calculated substitutional formation energy reveals that the dissolved Sc or Er in the Al matrix is very favorable to substitute the X sublattice site in L1_(2)-Al_(3)X(X=Sc/Er).The calculated solubility curve demonstrates the significant contribution of vibrational entropy to nucleation.The interface energies for Al/Al_(3)Sc,Al/Al_(3)Er and Al_(3)Sc/Al_(3)Er were calculated in the three directions of[100],[110]and[111],and we find that the interface structure in(100)plane is the most desirable,and the interface energy of Al/Al_(3)Er is the largest.Regardless of temperature and Sc/Er ratio,the L1_(2)-Al_(3)Sc_xEr_(1-x)precipitation phase mainly forms as the core-shell structure with Al3 Er as the core and Al_(3)Sc as the shell due to lower nucleation energy.The core-shell structure behaves higher stability once the particle radius is greater than 1 nm.Furthermore,the thermodynamic driving force for the segregating of Si or Zr in Al-Sc-Er alloy should accelerate the precipitation kinetics,where Si partitions occur preferentially to the Al_(3)Er and Zr partitions preferentially to the Al matrix.Overall,these theoretical results can offer solid explanations to the available experimental results.
