The effect of rare earth （RE） elements on the morphologies and sizes of Si phases in the hypereutectic A1-Si alloys modified with P was investigated. The results show that the addition of La element to the hypereute...The effect of rare earth （RE） elements on the morphologies and sizes of Si phases in the hypereutectic A1-Si alloys modified with P was investigated. The results show that the addition of La element to the hypereutectic A1-Si alloys can enhance the effect of P element on the modification of the primary Si phases. In the multiplex modification of RE-P, the primary Si phase is refiner and the shape of the eutectic Si is changed from long needle-like to short rod-like. Moreover, the agglomeration rate of the primary Si phase is slowed greatly. Even the melt is held for 6 h, the average size of the primary Si phase is still satisfied. The results analyzed by scanning electron microscope （SEM） indicate that La is richer at A1-Si interface than that in α-A1 or primary Si phase. The higher the La content in the A1-Si interface, the smaller the primary Si phase.展开更多
We report the detailed crystal structures and physical properties of Ru_(1-x)Mo_(x)alloys in the solid solution range of x=0.1-0.9.Structure characterizations indicate that the crystal structure changes from the hcp-M...We report the detailed crystal structures and physical properties of Ru_(1-x)Mo_(x)alloys in the solid solution range of x=0.1-0.9.Structure characterizations indicate that the crystal structure changes from the hcp-Mg-type,toβ-CrFe-type,and then bcc-W-type.The measurements of physical properties show that the Ru_(1-x)Mo_(x)samples with x≥0.2are superconductors and the superconducting transition temperature T_c as a function of Mo content exhibits a dome-like behavior.展开更多
We present results of an experimental study of magnetoresistance phenomenon in an amorphous silicon-nickel alloys a-Si1-yNiy:H:H (where y = 0.23) on the insulating side of the metal-insulator transition (MIT) in prese...We present results of an experimental study of magnetoresistance phenomenon in an amorphous silicon-nickel alloys a-Si1-yNiy:H:H (where y = 0.23) on the insulating side of the metal-insulator transition (MIT) in presence of magnetic field up to 4.5 T and at very low temperature. The electrical resistivity is found to follow the Efros-Shklovskii Variable Range Hopping regime (ES VRH) with T -1/2. This behaviour indicates the existence of the Coulomb gap (CG) near the Fermi level.展开更多
To clarify the corrosion mechanism associated with the precipitate of T1(Al2CuLi)in Al-Li alloys,the simulated bulk precipitate of T1 was fabricated through melting and casting.Its electrochemical behavior and couplin...To clarify the corrosion mechanism associated with the precipitate of T1(Al2CuLi)in Al-Li alloys,the simulated bulk precipitate of T1 was fabricated through melting and casting.Its electrochemical behavior and coupling behavior with α(Al)in 3.5% NaCl solution were investigated.Meanwhile,the simulated Al alloy containing T1 particle was prepared and its corrosion morphology was observed.The results show that there exists a dynamic conversion corrosion mechanism associated with the precipitate of T1.At the beginning,the precipitate of T1 is anodic to the alloy base and corrosion occurs on its surface.However,during its corrosion process,its potential moves to a positive direction with immersion time increasing,due to the preferential dissolution of Li and the enrichment of Cu.As a result,the corroded T1 becomes cathodic to the alloy base at a later stage,leading to the anodic dissolution and corrosion of the alloy base at its adjacent periphery.It is suggested that the localized corrosion associated with the precipitate of T1 in Al-Li alloys is caused by the alternate anodic dissolution of the T1 precipitate and the alloy base at its adjacent periphery.展开更多
The corrosion behavior of BFe10-1-1 alloy with different rare earth （RE） contents in simulated flowing marine water was investigated by X-ray diffractometer and scanning electron microscope （SEM）. It was demonstra...The corrosion behavior of BFe10-1-1 alloy with different rare earth （RE） contents in simulated flowing marine water was investigated by X-ray diffractometer and scanning electron microscope （SEM）. It was demonstrated that the corrosion rate of BFel0-1-1 alloy with the same chemical compositions in faster flow velocity of marine water was higher than that in a lower flow velocity of marine water. Fixing the flow velocity, BFe 10-1-1 alloy had the best flushing corrosion resistance when the RE content was 0.04wt.%. The consequence of such good corrosion resistance was attributed to the formation of compact protective film on alloy surface containing RE phase such as CeNis. The RE-contained film combines with other corrosion products firmly, which was difficult to fall off from the alloy surface in the flowing marine water. Additionally, SEM analysis confirmed that pitting mechanism, which would be transformed to spalling mechanism gradually with further increasing RE content, was the prevalent mechanism when the alloy contained 0.04wt.%RE.展开更多
The natural passive films forrned on Fe_(40)Ni_(40)P_(14)B_6 and Fe_(54.6)Ni_(38)Si_(4.1)B_(2.3)V_1 amorphous alloys long-term exposed in air have been studied by X-ray photoelectron spectroscopy (XPS) and Auger elect...The natural passive films forrned on Fe_(40)Ni_(40)P_(14)B_6 and Fe_(54.6)Ni_(38)Si_(4.1)B_(2.3)V_1 amorphous alloys long-term exposed in air have been studied by X-ray photoelectron spectroscopy (XPS) and Auger electron (including Ar+ ion depth profiling) spectroscopy (AES). The following aspects have been investigated: (1) chemical states of the elements in the films. binding energies and the chemical shifts measured by XPSf (2) structure and composition of the films fand (3) thickness of the passive films determined by AES depth profiling and XPS analysis.展开更多
This paper carries out first principles calculation of the structure, electronic and optical properties of BexZn1-xO alloys based on the density-functional theory for the compositions x = 0.0, 0.25, 0.5, 0.75, 1.0. Th...This paper carries out first principles calculation of the structure, electronic and optical properties of BexZn1-xO alloys based on the density-functional theory for the compositions x = 0.0, 0.25, 0.5, 0.75, 1.0. The lattice constants deviations of alloys obey Vegard＇s law well. The BexZn1-xO alloys have the direct band gap （Г-Г） character, and the bowing coefficients axe less than the available theoretical values. Moreover, it investigates in detail the optical properties （dielectric functions, absorption spectrum and refractive index） of these ternary mixed crystals. The obtained results agree well with the available theoretical and experimental values.展开更多
The electronic band structure of GaxIn1-xAs alloy is calculated by using the local empirical pseudo-potential method including the effective disorder potential in the virtual crystal approximation. The compositional e...The electronic band structure of GaxIn1-xAs alloy is calculated by using the local empirical pseudo-potential method including the effective disorder potential in the virtual crystal approximation. The compositional effect of the electronic energy band structure of this alloy is studied with composition x ranging from 0 to 1. Various physical quantities such as band gaps, bowing parameters, refractive indices, and high frequency dielectric constants of the considered alloys with different Ga concentrations are calculated. The effects of both temperature and hydrostatic pressure on the calculated quantities are studied. The obtained results are found to be in good agreement with the available experimental and published data.展开更多
To obtain the finer primary silicon crystals, the proprietary Al-P masteralloy was adopted to modify the eutectic Al-Si alloys and the most suitable modification process wasmade in the experiments. The SEM (Scanning E...To obtain the finer primary silicon crystals, the proprietary Al-P masteralloy was adopted to modify the eutectic Al-Si alloys and the most suitable modification process wasmade in the experiments. The SEM (Scanning Electron Microscope) and DSC (Differential ScanningCalorimeter) analysis indicate that the Al-P modifier has more advantages over Cu-P and Fe-Pmodifier in easily addition, no elemental alteration and less undercooling of primary silicon'ssolidification, which suggests the Al-P master alloy is an effective modifier of eutectic Al-Sialloys.展开更多
Super-high pressure(SHP)technique plays an increasing role in the fields of materials science and engineering.Herein,the Mg_(97)Zn_(1)Y_(2) alloy was heat-treated under SHP(6 GPa)by cubic-anvil large-volume press with...Super-high pressure(SHP)technique plays an increasing role in the fields of materials science and engineering.Herein,the Mg_(97)Zn_(1)Y_(2) alloy was heat-treated under SHP(6 GPa)by cubic-anvil large-volume press with six rams for 2 h in the temperature range of 500–1200℃.The microstructure and mechanical properties were investigated.The results indicated that the as-cast sample consists of α-Mg equiaxed dendrites and continuous lamellar long period stacking ordered(LPSO)phase in grain boundaries.After the SHP treatment,the LPSO phase is gradually replaced by eutectic phase(Mg,Zn)_(3)Y with increasing temperature.The microhardness and strength of sample prepared at 1100℃ under SHP treatment are significantly improved compared with the as-cast one at room temperature.The improved mechanical behaviors are mainly attributed to LPSO phase kink-banding strengthening at low temperature and the precipitation strengthening of a large amount of fine(Mg,Zn)_(3)Y particles at high temperature after SHP treatment.It reveals the SHP is an effective approach to prepare high performance Mg alloys.展开更多
The behavior of growth and coarsening of T-1(Al2CuLi) precipitates was comparatively studied by means of TEM technique in two Al-Li alloys 2090 and 2090+Ce (with cerium content less than 0.1% in mass fraction). Statis...The behavior of growth and coarsening of T-1(Al2CuLi) precipitates was comparatively studied by means of TEM technique in two Al-Li alloys 2090 and 2090+Ce (with cerium content less than 0.1% in mass fraction). Statistical analysis results show that T-1 precipitates in alloy 2090+Ce have smaller aspect ratio, which is connected with the more intersections between different T-1 variants in this alloy. It is also found that the variation of maximum length of T-1 precipitates with aging time can be obviously divided into two stages of growth and coarsening. The diffusion coefficients of solute atoms of Cu and Li are calculated via growth kinetics curves of T-1 precipitates. The results show that the diffusion of atom Cu plays a more important role in the formation of T-1 precipitates.展开更多
The Curie temperature increases but crystallization temperature decreases with the in- crease of Ga content,x,of amorphous(Fe_(1-x)Ga_x)_(77.5)Nd_4B_(18.5) alloys.The average magnetic moment of Fe atoms is almost a co...The Curie temperature increases but crystallization temperature decreases with the in- crease of Ga content,x,of amorphous(Fe_(1-x)Ga_x)_(77.5)Nd_4B_(18.5) alloys.The average magnetic moment of Fe atoms is almost a constant.By X-ray diffraction and ther- momagnetic measurements,the crystalline phases of the alloys,an unknown phase and α-(Fe,Ga)besides Fe_3 B as major one,were identified.The relationship between room temperature coercive field and Ga.content was also studied.展开更多
Al5Ti1B master alloy was produced by two-step method. Experimental results show that the structure of Al5TilB master alloy depends on that of AlTi and AlB master alloys, the morphologies of TiAl3 depend on AlTi master...Al5Ti1B master alloy was produced by two-step method. Experimental results show that the structure of Al5TilB master alloy depends on that of AlTi and AlB master alloys, the morphologies of TiAl3 depend on AlTi master alloy and the boride phases depend on AlB master alloy. There are remarkable structure heredity between Al5Ti1B master alloy and AlTi, AlB master alloys. Theoretical analyses show that AlTi and Al-B master alloys can change the melt structure of Al5Ti1B master alloy, then affect the solid structure of the master alloy.展开更多
A theoretical calculation of the miscibility gap with considering the mismatch strain and elastic parameters was performed for the GaN1-xPx ternary alloys on (0001) GaN/sapphire substrates based on the strictly regula...A theoretical calculation of the miscibility gap with considering the mismatch strain and elastic parameters was performed for the GaN1-xPx ternary alloys on (0001) GaN/sapphire substrates based on the strictly regular solution model. The calculated results show that the boundary of the spinodal isotherm shifts from x=0.06 to x=0.25 at the growth temperature of 1200 K as the strain factor increases from 0 to 1, indicating that the strain in the GaN1-xPx layers can suppress the phase separation. Meanwhile, with the increase of the effective elastic parameters of GaN and GaP, the available maximum P content also increases slightly at the growing temperature.展开更多
The phase component and Curie tempemture of Nd4(Fe1-xCrx)77.5B18.5 (0 <x <0.25) alloys have been studied. X-ray diffraction analysis shows the presence of α-Fe and Fe3B phases in the samples with x < 0.1 and...The phase component and Curie tempemture of Nd4(Fe1-xCrx)77.5B18.5 (0 <x <0.25) alloys have been studied. X-ray diffraction analysis shows the presence of α-Fe and Fe3B phases in the samples with x < 0.1 and the presence of α-Fe, Nd2Fe14B and Fe2B phases in the samples with x > 0.1. The magnetic measurement shows that Curie temperutures of Fe3B and Nd2Fe14B phases decrease with increasing Cr content. The influence of the substitution of Cr for Fe was discussed.展开更多
基金supported by the National Natural Science Foundation of China （Grant No.50075051）
文摘The effect of rare earth （RE） elements on the morphologies and sizes of Si phases in the hypereutectic A1-Si alloys modified with P was investigated. The results show that the addition of La element to the hypereutectic A1-Si alloys can enhance the effect of P element on the modification of the primary Si phases. In the multiplex modification of RE-P, the primary Si phase is refiner and the shape of the eutectic Si is changed from long needle-like to short rod-like. Moreover, the agglomeration rate of the primary Si phase is slowed greatly. Even the melt is held for 6 h, the average size of the primary Si phase is still satisfied. The results analyzed by scanning electron microscope （SEM） indicate that La is richer at A1-Si interface than that in α-A1 or primary Si phase. The higher the La content in the A1-Si interface, the smaller the primary Si phase.
基金Project supported by Beijing Natural Science Foundation (Grant No.Z200005)the National Key R&D Program of China (Grant Nos.2018YFE0202600 and 2022YFA1403800)+1 种基金the National Natural Science Foundation of China (Grant No.12274459)Beijing National Laboratory for Condensed Matter Physics,and Collaborative Research Project of Laboratory for Materials and Structures,Institute of Innovative Research,Tokyo Institute of Technology。
文摘We report the detailed crystal structures and physical properties of Ru_(1-x)Mo_(x)alloys in the solid solution range of x=0.1-0.9.Structure characterizations indicate that the crystal structure changes from the hcp-Mg-type,toβ-CrFe-type,and then bcc-W-type.The measurements of physical properties show that the Ru_(1-x)Mo_(x)samples with x≥0.2are superconductors and the superconducting transition temperature T_c as a function of Mo content exhibits a dome-like behavior.
文摘We present results of an experimental study of magnetoresistance phenomenon in an amorphous silicon-nickel alloys a-Si1-yNiy:H:H (where y = 0.23) on the insulating side of the metal-insulator transition (MIT) in presence of magnetic field up to 4.5 T and at very low temperature. The electrical resistivity is found to follow the Efros-Shklovskii Variable Range Hopping regime (ES VRH) with T -1/2. This behaviour indicates the existence of the Coulomb gap (CG) near the Fermi level.
基金Project(50401012) supported by the National Natural Science Foundation of China
文摘To clarify the corrosion mechanism associated with the precipitate of T1(Al2CuLi)in Al-Li alloys,the simulated bulk precipitate of T1 was fabricated through melting and casting.Its electrochemical behavior and coupling behavior with α(Al)in 3.5% NaCl solution were investigated.Meanwhile,the simulated Al alloy containing T1 particle was prepared and its corrosion morphology was observed.The results show that there exists a dynamic conversion corrosion mechanism associated with the precipitate of T1.At the beginning,the precipitate of T1 is anodic to the alloy base and corrosion occurs on its surface.However,during its corrosion process,its potential moves to a positive direction with immersion time increasing,due to the preferential dissolution of Li and the enrichment of Cu.As a result,the corroded T1 becomes cathodic to the alloy base at a later stage,leading to the anodic dissolution and corrosion of the alloy base at its adjacent periphery.It is suggested that the localized corrosion associated with the precipitate of T1 in Al-Li alloys is caused by the alternate anodic dissolution of the T1 precipitate and the alloy base at its adjacent periphery.
基金supported by the Science and Technology Payoffs Transformation Program of Jiangsu Province (DA2006034)the Program of National College Student Creative Experiment (081053309)
文摘The corrosion behavior of BFe10-1-1 alloy with different rare earth （RE） contents in simulated flowing marine water was investigated by X-ray diffractometer and scanning electron microscope （SEM）. It was demonstrated that the corrosion rate of BFel0-1-1 alloy with the same chemical compositions in faster flow velocity of marine water was higher than that in a lower flow velocity of marine water. Fixing the flow velocity, BFe 10-1-1 alloy had the best flushing corrosion resistance when the RE content was 0.04wt.%. The consequence of such good corrosion resistance was attributed to the formation of compact protective film on alloy surface containing RE phase such as CeNis. The RE-contained film combines with other corrosion products firmly, which was difficult to fall off from the alloy surface in the flowing marine water. Additionally, SEM analysis confirmed that pitting mechanism, which would be transformed to spalling mechanism gradually with further increasing RE content, was the prevalent mechanism when the alloy contained 0.04wt.%RE.
文摘The natural passive films forrned on Fe_(40)Ni_(40)P_(14)B_6 and Fe_(54.6)Ni_(38)Si_(4.1)B_(2.3)V_1 amorphous alloys long-term exposed in air have been studied by X-ray photoelectron spectroscopy (XPS) and Auger electron (including Ar+ ion depth profiling) spectroscopy (AES). The following aspects have been investigated: (1) chemical states of the elements in the films. binding energies and the chemical shifts measured by XPSf (2) structure and composition of the films fand (3) thickness of the passive films determined by AES depth profiling and XPS analysis.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10974139 and 10964002)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20050610010)+1 种基金the Science-Technology Foundation of Guizhou Province of China (Grant Nos. [2009]2066,[2009]06 and [2010]2146)the Project of Aiding Elites’ Research Condition of Guizhou Province of China (Grant No. TZJF-2008-42)
文摘This paper carries out first principles calculation of the structure, electronic and optical properties of BexZn1-xO alloys based on the density-functional theory for the compositions x = 0.0, 0.25, 0.5, 0.75, 1.0. The lattice constants deviations of alloys obey Vegard＇s law well. The BexZn1-xO alloys have the direct band gap （Г-Г） character, and the bowing coefficients axe less than the available theoretical values. Moreover, it investigates in detail the optical properties （dielectric functions, absorption spectrum and refractive index） of these ternary mixed crystals. The obtained results agree well with the available theoretical and experimental values.
文摘The electronic band structure of GaxIn1-xAs alloy is calculated by using the local empirical pseudo-potential method including the effective disorder potential in the virtual crystal approximation. The compositional effect of the electronic energy band structure of this alloy is studied with composition x ranging from 0 to 1. Various physical quantities such as band gaps, bowing parameters, refractive indices, and high frequency dielectric constants of the considered alloys with different Ga concentrations are calculated. The effects of both temperature and hydrostatic pressure on the calculated quantities are studied. The obtained results are found to be in good agreement with the available experimental and published data.
基金The work was financially supported by National Natural Science Foundation of China (No.50071028) Nature Science Foundation of Shandong Province of China (No.L2000F01).
文摘To obtain the finer primary silicon crystals, the proprietary Al-P masteralloy was adopted to modify the eutectic Al-Si alloys and the most suitable modification process wasmade in the experiments. The SEM (Scanning Electron Microscope) and DSC (Differential ScanningCalorimeter) analysis indicate that the Al-P modifier has more advantages over Cu-P and Fe-Pmodifier in easily addition, no elemental alteration and less undercooling of primary silicon'ssolidification, which suggests the Al-P master alloy is an effective modifier of eutectic Al-Sialloys.
基金NSFC(51101142 and 50821001)New Century Excellent Talents in University of Ministry of Education of China(NCET-12-0690)+1 种基金Hebei province scientific program(13961002D and Y2012019)Hebei Province Technology Foundation for Selected Overseas Chinese and Outstanding Young Scholar.
文摘Super-high pressure(SHP)technique plays an increasing role in the fields of materials science and engineering.Herein,the Mg_(97)Zn_(1)Y_(2) alloy was heat-treated under SHP(6 GPa)by cubic-anvil large-volume press with six rams for 2 h in the temperature range of 500–1200℃.The microstructure and mechanical properties were investigated.The results indicated that the as-cast sample consists of α-Mg equiaxed dendrites and continuous lamellar long period stacking ordered(LPSO)phase in grain boundaries.After the SHP treatment,the LPSO phase is gradually replaced by eutectic phase(Mg,Zn)_(3)Y with increasing temperature.The microhardness and strength of sample prepared at 1100℃ under SHP treatment are significantly improved compared with the as-cast one at room temperature.The improved mechanical behaviors are mainly attributed to LPSO phase kink-banding strengthening at low temperature and the precipitation strengthening of a large amount of fine(Mg,Zn)_(3)Y particles at high temperature after SHP treatment.It reveals the SHP is an effective approach to prepare high performance Mg alloys.
文摘The behavior of growth and coarsening of T-1(Al2CuLi) precipitates was comparatively studied by means of TEM technique in two Al-Li alloys 2090 and 2090+Ce (with cerium content less than 0.1% in mass fraction). Statistical analysis results show that T-1 precipitates in alloy 2090+Ce have smaller aspect ratio, which is connected with the more intersections between different T-1 variants in this alloy. It is also found that the variation of maximum length of T-1 precipitates with aging time can be obviously divided into two stages of growth and coarsening. The diffusion coefficients of solute atoms of Cu and Li are calculated via growth kinetics curves of T-1 precipitates. The results show that the diffusion of atom Cu plays a more important role in the formation of T-1 precipitates.
文摘The Curie temperature increases but crystallization temperature decreases with the in- crease of Ga content,x,of amorphous(Fe_(1-x)Ga_x)_(77.5)Nd_4B_(18.5) alloys.The average magnetic moment of Fe atoms is almost a constant.By X-ray diffraction and ther- momagnetic measurements,the crystalline phases of the alloys,an unknown phase and α-(Fe,Ga)besides Fe_3 B as major one,were identified.The relationship between room temperature coercive field and Ga.content was also studied.
文摘Al5Ti1B master alloy was produced by two-step method. Experimental results show that the structure of Al5TilB master alloy depends on that of AlTi and AlB master alloys, the morphologies of TiAl3 depend on AlTi master alloy and the boride phases depend on AlB master alloy. There are remarkable structure heredity between Al5Ti1B master alloy and AlTi, AlB master alloys. Theoretical analyses show that AlTi and Al-B master alloys can change the melt structure of Al5Ti1B master alloy, then affect the solid structure of the master alloy.
基金Project supported by the National Natural Science Foundation of China (60406002, 60325413 and 60136020), the Natural Science Foundation of Jiangsu Province (BK2003411)
文摘A theoretical calculation of the miscibility gap with considering the mismatch strain and elastic parameters was performed for the GaN1-xPx ternary alloys on (0001) GaN/sapphire substrates based on the strictly regular solution model. The calculated results show that the boundary of the spinodal isotherm shifts from x=0.06 to x=0.25 at the growth temperature of 1200 K as the strain factor increases from 0 to 1, indicating that the strain in the GaN1-xPx layers can suppress the phase separation. Meanwhile, with the increase of the effective elastic parameters of GaN and GaP, the available maximum P content also increases slightly at the growing temperature.
文摘The phase component and Curie tempemture of Nd4(Fe1-xCrx)77.5B18.5 (0 <x <0.25) alloys have been studied. X-ray diffraction analysis shows the presence of α-Fe and Fe3B phases in the samples with x < 0.1 and the presence of α-Fe, Nd2Fe14B and Fe2B phases in the samples with x > 0.1. The magnetic measurement shows that Curie temperutures of Fe3B and Nd2Fe14B phases decrease with increasing Cr content. The influence of the substitution of Cr for Fe was discussed.
