Through sampling from different depth and different zones in the zinc bath, the size distribution of dross particles built during galvannealed （GA） production is analyzed and compared with that during galvanized （G...Through sampling from different depth and different zones in the zinc bath, the size distribution of dross particles built during galvannealed （GA） production is analyzed and compared with that during galvanized （GI） production. The relationship between the dross formation during transitions from GA to GI and the effective Al of the melt is discussed. Finally, the characteristics of dross particles in GA coating and its effects on GA punching and painting performances are studied.展开更多
A series of K-promoted Pt/Al2O3 catalysts were tested for CO oxidation. It was found that the addition of K significantly enhanced the activity. A detailed kinetic study showed that the activation energies of the K-co...A series of K-promoted Pt/Al2O3 catalysts were tested for CO oxidation. It was found that the addition of K significantly enhanced the activity. A detailed kinetic study showed that the activation energies of the K-containing catalysts were lower than those of the K-free ones, particularly for catalysts with high Pt contents （51.6 k）/mol for 0.42K-2.0Pt/Al2O3 and 6：3.6 kJ/mol for 2.0Pt/Al2O3 ）. The CO reaction orders were higher for the K-containing catalysts （about -0.2） than for the K-free ones （about -0.5）, with the former having much lower equilibrium constants for CO adsorption than the latter. In situ Fourier-transform infrared spectroscopy showed that surface CO desorption from the 0.42K-2.0Pt/Al2O3 catalyst was easier than from 2.0Pt/Al2O3. The promoting effect of K was therefore caused by weakening of the interactions between CO and surface Pt atoms. This decreased coverage of the catalyst with CO and facilitated competitive O2 chemisorption on the Pt surface, and significantly lowered the reaction barrier between chemisorbed CO and O2 species.展开更多
The structure of the solid solution treated and deformed Fe-25Mn-(0-3.11)Al-0.15C alloys was examined by means of metallograph and X-ray diffraction, which has confirmed that Al restrains the γ→ε transformation in ...The structure of the solid solution treated and deformed Fe-25Mn-(0-3.11)Al-0.15C alloys was examined by means of metallograph and X-ray diffraction, which has confirmed that Al restrains the γ→ε transformation in the Fe-Mn alloys. The mechanism on the restraining effect of Al has been discussed on the basis of the efFect of Al upon the stacking fault energy in the Fe-Mn alloys.Aluminium increases thermodynamically the stability of the Fe-Mn austenite and the driving force limit necessitated to be overcome for the γ→ε transformation, because the thermodynamicalcalculation indicates that Al increases the stacking fault energy in the Fe-Mn alloys at 300 K.Al will decrease the number and the size for the ε-martensite nucleus according to the stacking fault mechanism of the ε-martensite nucleation展开更多
The microplasma oxidation process of LY 12 Al alloy in Na2SiO3-KOH-NaAL2 system has been studied. The voltage-time curve of oxidation process is changed with the variation of current ...The microplasma oxidation process of LY 12 Al alloy in Na2SiO3-KOH-NaAL2 system has been studied. The voltage-time curve of oxidation process is changed with the variation of current densities. The voltage breakdown and hardness of coating increase with increasing current density. The phase composition, morphologies, element and the distribution of ceramic coating are investigated by XRD, EPMA.展开更多
The electroplastic（EP） tensile properties of 5A90 Al–Li alloys compared with thermal tension were investigated.The microstructural variation at different conditions was observed by SEM and TEM.The current density s...The electroplastic（EP） tensile properties of 5A90 Al–Li alloys compared with thermal tension were investigated.The microstructural variation at different conditions was observed by SEM and TEM.The current density significantly influences the elongation and the flow stress.With increasing current density,wider and deeper dimples on the fracture surfaces and less dislocation density and pile-ups in the EP tension samples were observed compared with roomtemperature and thermal tension,which indicates the plasticity improvement and flow stress reduction.The EP effect（EPE） mainly results from a comprehensive function of Joule heating and pure EPE.Among them,Joule heating effect is perhaps a dominant factor.展开更多
Because of the discrete charge storage mechanism, charge trapping memory（CTM） technique is a good candidate for aerospace and military missions. The total ionization dose（TID） effects on CTM cells with Al2O3/HfO2/...Because of the discrete charge storage mechanism, charge trapping memory（CTM） technique is a good candidate for aerospace and military missions. The total ionization dose（TID） effects on CTM cells with Al2O3/HfO2/Al2O3（AHA） high-k gate stack structure under in-situ 10 keV x-rays are studied. The C-V characteristics at different radiation doses demonstrate that charge stored in the device continues to be leaked away during the irradiation,thereby inducing the shift of flat band voltage（V（fb））. The dc memory window shows insignificant changes, suggesting the existence of good P/E ability. Furthermore, the physical mechanisms of TID induced radiation damages in AHA-based CTM are analyzed.展开更多
The glass-forming ability （CFA） and magnetic properties of the Cd50 Co50-based amorphous alloy with AI addition substitution for Co are investigated. It is found that the CFA and magneto-caloric effect of the Gd50Co...The glass-forming ability （CFA） and magnetic properties of the Cd50 Co50-based amorphous alloy with AI addition substitution for Co are investigated. It is found that the CFA and magneto-caloric effect of the Gd50Co45Al5 amorphous alloy are better than Cd50Co50 amorphous alloy. The maximum magnetic entropy change （-△ Sm^peak） and the magnetic refrigerant capacity- of the amorphous alloy under a field of 5 T are about 6.64 J·kg^-1 K^-1 and 764 J·kg^-1, respectively. The field dependence of magnetic entropy change meets the one predicted by the mean field theory, which is investigated for a better understanding of the magneto-caloric behaviors of the Gdso Co45Al5 amorphous alloy.展开更多
The Portevin–Le Chatelier（PLC） effect in Al–2.30wt%Mg, Al–4.57wt%Mg and Al–6.91wt%Mg alloys has been investigated at various applied strain rates at room temperature in this study. Three-dimensional digital imag...The Portevin–Le Chatelier（PLC） effect in Al–2.30wt%Mg, Al–4.57wt%Mg and Al–6.91wt%Mg alloys has been investigated at various applied strain rates at room temperature in this study. Three-dimensional digital image correlation（3D-DIC） technique was applied to obtaining the further insight into the spatiotemporal characteristics, in particular the influence of Mg content on deformation behaviors. Mg content has a pronounced effect on serration characteristics, including the serration type and amplitude; Mg content tends to weaken the spatial correlation of the propagative bands. Additionally, the serration amplitude linearly increases with the maximum PLC band strain; high Mg content generates a higher PLC band strain at a given serration amplitude compared with low Mg content. Mg content is found to be effective to enhance the serration amplitude, the maximum PLC band strain and also the amount of elastic shrinkage outside PLC bands.展开更多
Substantial defects are produced in Al2O3 by 4 MeV Au ion irradiation with a fluence of 4.4×10^15 cm^-2. Ruther- ford baekscattering spectrometry/channeling and cross-sectional transmission electron microscopy me...Substantial defects are produced in Al2O3 by 4 MeV Au ion irradiation with a fluence of 4.4×10^15 cm^-2. Ruther- ford baekscattering spectrometry/channeling and cross-sectional transmission electron microscopy methods are used to investigate the irradiation damage. The 190keV H ions with a fuence of 1×10^17 cm^-2 are used for implanting pristine and Au ion irradiated Al2O3 to explore the irradiation damage effects on the hydrogen retention in Al2O3. The time-of-flight secondary ion mass spectrometry method is used to obtaJn the single hydrogen depth profile and ions mass spectra （IMS）, in which we find that implanted hydrogens interacted with defects produced by Au ion irradiation. In IMS, we also obtain the hydrogen retention at a certain depth. Comparing the hydrogen retention in different Al2O3 samples, it is concluded that the irradiation damage improves the tritium permeation resistance property of Al2O3 under given conditions. This result means that Al2O3 may strengthen its property of reduc/ng tritium permeation under the harsh irradiation environment in fusion reactors.展开更多
The ultrathin aluminum films with thickness in the range of 2～60 nm have been deposited by dc magnetron sputtering apparatus. Reflectance and transmittance of the obtained samples were measured with a WFZ-900-D4 UV/V...The ultrathin aluminum films with thickness in the range of 2～60 nm have been deposited by dc magnetron sputtering apparatus. Reflectance and transmittance of the obtained samples were measured with a WFZ-900-D4 UV/VIS spectrophotometer. The optical constant (n, k) and permittivity (ε', ε') were determined by applying Newton-Simpson recurrent substitution method. The results indicate that the electromagnetic constitutive characteristic of ultrathin aluminum films is a function of thickness and has obvious size effect.展开更多
The oxidation behaviours of pure 77,Ti-11 at% Al and Ti-11 at% Al-Nd alloys in air at the tempera- ture range 800～1000℃ have been investigated in the present paper.Their oxidation kinetics follows substantially the ...The oxidation behaviours of pure 77,Ti-11 at% Al and Ti-11 at% Al-Nd alloys in air at the tempera- ture range 800～1000℃ have been investigated in the present paper.Their oxidation kinetics follows substantially the parabolic rate law.The activation energies of oxidation processes are 103 and 91 kcal/mole for Ti-11 Al and Ti-11 Al-Nd alloys,respectively.The platinum wire tagging tests have shown that oxygen atoms diffuse into the substrate during oxidation of pure Ti and that Ti,Al and Nd atoms diffuse across a scale of oxides outwards during oxidations of these alloys.Nd addition promotes the selective oxidation of aluminium.The addition of Al and Nd decreases the extent of penetration of oxygen atoms into the Ti substrate.The X-ray diffraction analysis confirms that the oxide scales of the alloys consist of TiO_2 and α-Al_2O_3,or TiO_2,α-Al_2O_3 and a small amount of Nd_2O_3 for Ti-11 Al and Ti-11 Al-Nd alloys, respectively.展开更多
The main Iimitation to the toughening of the α-Al2O3/Ni composite is the poor bonding atthe interface. which causes the nickel particles to be pulled-out during crack propagation with-out obvious plastic deformation....The main Iimitation to the toughening of the α-Al2O3/Ni composite is the poor bonding atthe interface. which causes the nickel particles to be pulled-out during crack propagation with-out obvious plastic deformation. A proper control of oxygen content at the Al2O3-Ni interfacecan promote wetting at the intedece, and produce a mechanically interlocked and chemically strengthened intedece, causing most of the nickel particles to be stretched to failure and to expe-rience severe plastic deformation during crack propagation in the composite. Fracture toughnesstesting using a modified double cantilever beam method with in situ observation of crack prop-agation in a scanning electron microscope shows that the composite with the strengthenedinterface has a more desirable R-curve behaviour and a higher fracture toughness value than thenormal composite.展开更多
The effects of ternary solutes Ti, Co, V, Cr, Ta, W and Mo on the D03 phase 5tability of Fe3Alintermetallics are investigated by tight-binding linear Muffin-tin orbitaI method. The predictedsite preference5 of these e...The effects of ternary solutes Ti, Co, V, Cr, Ta, W and Mo on the D03 phase 5tability of Fe3Alintermetallics are investigated by tight-binding linear Muffin-tin orbitaI method. The predictedsite preference5 of these elements in Fe3AI are in agreement with the experimental observations.The calculated Iocal magnetic moment of Fe3AI is identical to the experimentaI. ln addition, itis found that the D03 phase stability of Fe3AI doped with Ti, V, Co and Cr depends on 'energygap- of energy band near Fermi level. while the D03 phase stability of Fe3AI doped with Ta, Wand Mo may be affected by Madelung energy.展开更多
By use of self-consistent field Xα scattered-wave (SCF-Xα-SW) method, the electronic structure was calculated for four models of Ti4Al14X (X=Al, Fe, Ni and Cu) clusters. The Ti4Al14X cluster was developed based on L...By use of self-consistent field Xα scattered-wave (SCF-Xα-SW) method, the electronic structure was calculated for four models of Ti4Al14X (X=Al, Fe, Ni and Cu) clusters. The Ti4Al14X cluster was developed based on L12 Al3Ti-base intermetallic compound. The results are presented using the density of states (DOS) and one-electron properties, such as relative binding tendency between the atom and the model cluster, and hybrid bonding tendency between the alloying element and the host atoms. By comparing the four models of Ti4Al14X cluster, the effect of the Fe, Ni or Cu atom on the physical properties of Al3Ti-based L12 intermetallic compounds is analyzed. The results indicate that the addition of the Fe, Ni or Cu atom intensifies the relative binding tendency between Ti atom and Ti4Al14X cluster. It was found that the Fermi level (EF) lies in a maximum in the DOS for Ti4Al14Al cluster; on the contrary, the EF comes near a minimum tn the DOS for Ti4Al14X (X=Fe, Ni and Cu) cluster. Thus the L12 crystal structure for binary Al3Ti alloy is unstable, and the addition of the Fe, Ni or Cu atom to Al3Ti is benefical to stabilize L12 crystal structure. The calculation also shows that the Fe, Ni or Cu atom strengthens the hybrid bonding tendency between the central atom and the host atoms for Ti4Al14X cluster and thereby may lead to the constriction of the lattice of Al3Ti-base intermetallic compounds.展开更多
MAKAROV and Trontelj first reported the WO<sub>3</sub>-based low voltage varistor material doped with MnO<sub>2</sub> and Na<sub>2</sub>CO<sub>3</sub> in 1994. This mate...MAKAROV and Trontelj first reported the WO<sub>3</sub>-based low voltage varistor material doped with MnO<sub>2</sub> and Na<sub>2</sub>CO<sub>3</sub> in 1994. This material is worth further study because of its low threshold voltage （ 【 10 V/mm）. We have found that the doping of Co<sub>2</sub>O<sub>3</sub> can obviously improve the nonlinearity of WO<sub>3</sub>-MnO<sub>2</sub>-Na<sub>2</sub>CO<sub>3</sub> series with nonlinear coefficient α≈ 2,and a may be higher than 5 when the amount of Co<sub>2</sub>O<sub>3</sub> is 1% （mole percentage）. However, the nonlinear characteristic almost vanished when 0.5% Al<sub>2</sub>O<sub>3</sub> was doped into this system at room temperature, and Al<sub>2</sub>O<sub>3</sub> showed very stable展开更多
We address the effects of processing parameters on residual stresses and fatigue properties of LY2 Al alloy by laser shock processing （LSP）. Results show that compressive residual stresses are generated near the sur...We address the effects of processing parameters on residual stresses and fatigue properties of LY2 Al alloy by laser shock processing （LSP）. Results show that compressive residual stresses are generated near the surface of samples due to LSP. The maximum compressive residual stress at the surface by two LSP impacts on one side is higher than that by one LSP impact. The maximum value of tensile residual stress is found at the mid-plane of samples subjected to two-sided LSP. Compared with fatigue lives of samples treated by single-sided LSP, lives of those treated by two-sided LSP are lower. However, these are higher than untreated ones.展开更多
文摘Through sampling from different depth and different zones in the zinc bath, the size distribution of dross particles built during galvannealed （GA） production is analyzed and compared with that during galvanized （GI） production. The relationship between the dross formation during transitions from GA to GI and the effective Al of the melt is discussed. Finally, the characteristics of dross particles in GA coating and its effects on GA punching and painting performances are studied.
基金financially supported by the National Natural Science Foundation of China(21173195)~~
文摘A series of K-promoted Pt/Al2O3 catalysts were tested for CO oxidation. It was found that the addition of K significantly enhanced the activity. A detailed kinetic study showed that the activation energies of the K-containing catalysts were lower than those of the K-free ones, particularly for catalysts with high Pt contents （51.6 k）/mol for 0.42K-2.0Pt/Al2O3 and 6：3.6 kJ/mol for 2.0Pt/Al2O3 ）. The CO reaction orders were higher for the K-containing catalysts （about -0.2） than for the K-free ones （about -0.5）, with the former having much lower equilibrium constants for CO adsorption than the latter. In situ Fourier-transform infrared spectroscopy showed that surface CO desorption from the 0.42K-2.0Pt/Al2O3 catalyst was easier than from 2.0Pt/Al2O3. The promoting effect of K was therefore caused by weakening of the interactions between CO and surface Pt atoms. This decreased coverage of the catalyst with CO and facilitated competitive O2 chemisorption on the Pt surface, and significantly lowered the reaction barrier between chemisorbed CO and O2 species.
文摘The structure of the solid solution treated and deformed Fe-25Mn-(0-3.11)Al-0.15C alloys was examined by means of metallograph and X-ray diffraction, which has confirmed that Al restrains the γ→ε transformation in the Fe-Mn alloys. The mechanism on the restraining effect of Al has been discussed on the basis of the efFect of Al upon the stacking fault energy in the Fe-Mn alloys.Aluminium increases thermodynamically the stability of the Fe-Mn austenite and the driving force limit necessitated to be overcome for the γ→ε transformation, because the thermodynamicalcalculation indicates that Al increases the stacking fault energy in the Fe-Mn alloys at 300 K.Al will decrease the number and the size for the ε-martensite nucleus according to the stacking fault mechanism of the ε-martensite nucleation
文摘The microplasma oxidation process of LY 12 Al alloy in Na2SiO3-KOH-NaAL2 system has been studied. The voltage-time curve of oxidation process is changed with the variation of current densities. The voltage breakdown and hardness of coating increase with increasing current density. The phase composition, morphologies, element and the distribution of ceramic coating are investigated by XRD, EPMA.
基金financially supported by the National Natural Science Foundation of China (No.51105248)
文摘The electroplastic（EP） tensile properties of 5A90 Al–Li alloys compared with thermal tension were investigated.The microstructural variation at different conditions was observed by SEM and TEM.The current density significantly influences the elongation and the flow stress.With increasing current density,wider and deeper dimples on the fracture surfaces and less dislocation density and pile-ups in the EP tension samples were observed compared with roomtemperature and thermal tension,which indicates the plasticity improvement and flow stress reduction.The EP effect（EPE） mainly results from a comprehensive function of Joule heating and pure EPE.Among them,Joule heating effect is perhaps a dominant factor.
基金Supported by the National Natural Science Foundation of China under Grant No 616340084the Youth Innovation Promotion Association of Chinese Academy of Sciences under Grant No 2014101+1 种基金the International Cooperation Project of Chinese Academy of Sciencesthe Austrian-Chinese Cooperative R&D Projects under Grant No 172511KYSB20150006
文摘Because of the discrete charge storage mechanism, charge trapping memory（CTM） technique is a good candidate for aerospace and military missions. The total ionization dose（TID） effects on CTM cells with Al2O3/HfO2/Al2O3（AHA） high-k gate stack structure under in-situ 10 keV x-rays are studied. The C-V characteristics at different radiation doses demonstrate that charge stored in the device continues to be leaked away during the irradiation,thereby inducing the shift of flat band voltage（V（fb））. The dc memory window shows insignificant changes, suggesting the existence of good P/E ability. Furthermore, the physical mechanisms of TID induced radiation damages in AHA-based CTM are analyzed.
基金Supported by the National Natural Science Foundation of China under Grant Nos 51171100 and 51271103the Research Grants Council of the Hong Kong Special Administrative Region under Grant No PolyU511212
文摘The glass-forming ability （CFA） and magnetic properties of the Cd50 Co50-based amorphous alloy with AI addition substitution for Co are investigated. It is found that the CFA and magneto-caloric effect of the Gd50Co45Al5 amorphous alloy are better than Cd50Co50 amorphous alloy. The maximum magnetic entropy change （-△ Sm^peak） and the magnetic refrigerant capacity- of the amorphous alloy under a field of 5 T are about 6.64 J·kg^-1 K^-1 and 764 J·kg^-1, respectively. The field dependence of magnetic entropy change meets the one predicted by the mean field theory, which is investigated for a better understanding of the magneto-caloric behaviors of the Gdso Co45Al5 amorphous alloy.
基金financial support received from the National Natural Science Foundation of China (NSFC) under Grant Nos. 11332010, 51571013, 51271174, 11472266 and 11428206
文摘The Portevin–Le Chatelier（PLC） effect in Al–2.30wt%Mg, Al–4.57wt%Mg and Al–6.91wt%Mg alloys has been investigated at various applied strain rates at room temperature in this study. Three-dimensional digital image correlation（3D-DIC） technique was applied to obtaining the further insight into the spatiotemporal characteristics, in particular the influence of Mg content on deformation behaviors. Mg content has a pronounced effect on serration characteristics, including the serration type and amplitude; Mg content tends to weaken the spatial correlation of the propagative bands. Additionally, the serration amplitude linearly increases with the maximum PLC band strain; high Mg content generates a higher PLC band strain at a given serration amplitude compared with low Mg content. Mg content is found to be effective to enhance the serration amplitude, the maximum PLC band strain and also the amount of elastic shrinkage outside PLC bands.
基金Supported by the National Natural Science Foundation of China under Grant Nos 91426304 and 91226202the National Magnetic Confinement Fusion Energy Research Project under Grant No 2015GB113000
文摘Substantial defects are produced in Al2O3 by 4 MeV Au ion irradiation with a fluence of 4.4×10^15 cm^-2. Ruther- ford baekscattering spectrometry/channeling and cross-sectional transmission electron microscopy methods are used to investigate the irradiation damage. The 190keV H ions with a fuence of 1×10^17 cm^-2 are used for implanting pristine and Au ion irradiated Al2O3 to explore the irradiation damage effects on the hydrogen retention in Al2O3. The time-of-flight secondary ion mass spectrometry method is used to obtaJn the single hydrogen depth profile and ions mass spectra （IMS）, in which we find that implanted hydrogens interacted with defects produced by Au ion irradiation. In IMS, we also obtain the hydrogen retention at a certain depth. Comparing the hydrogen retention in different Al2O3 samples, it is concluded that the irradiation damage improves the tritium permeation resistance property of Al2O3 under given conditions. This result means that Al2O3 may strengthen its property of reduc/ng tritium permeation under the harsh irradiation environment in fusion reactors.
基金the Advance FOundation of National Defense is greatly appreciated.
文摘The ultrathin aluminum films with thickness in the range of 2～60 nm have been deposited by dc magnetron sputtering apparatus. Reflectance and transmittance of the obtained samples were measured with a WFZ-900-D4 UV/VIS spectrophotometer. The optical constant (n, k) and permittivity (ε', ε') were determined by applying Newton-Simpson recurrent substitution method. The results indicate that the electromagnetic constitutive characteristic of ultrathin aluminum films is a function of thickness and has obvious size effect.
基金This work was financially supported by the Corrosion Science Laboratory,Academia Sinica
文摘The oxidation behaviours of pure 77,Ti-11 at% Al and Ti-11 at% Al-Nd alloys in air at the tempera- ture range 800～1000℃ have been investigated in the present paper.Their oxidation kinetics follows substantially the parabolic rate law.The activation energies of oxidation processes are 103 and 91 kcal/mole for Ti-11 Al and Ti-11 Al-Nd alloys,respectively.The platinum wire tagging tests have shown that oxygen atoms diffuse into the substrate during oxidation of pure Ti and that Ti,Al and Nd atoms diffuse across a scale of oxides outwards during oxidations of these alloys.Nd addition promotes the selective oxidation of aluminium.The addition of Al and Nd decreases the extent of penetration of oxygen atoms into the Ti substrate.The X-ray diffraction analysis confirms that the oxide scales of the alloys consist of TiO_2 and α-Al_2O_3,or TiO_2,α-Al_2O_3 and a small amount of Nd_2O_3 for Ti-11 Al and Ti-11 Al-Nd alloys, respectively.
文摘The main Iimitation to the toughening of the α-Al2O3/Ni composite is the poor bonding atthe interface. which causes the nickel particles to be pulled-out during crack propagation with-out obvious plastic deformation. A proper control of oxygen content at the Al2O3-Ni interfacecan promote wetting at the intedece, and produce a mechanically interlocked and chemically strengthened intedece, causing most of the nickel particles to be stretched to failure and to expe-rience severe plastic deformation during crack propagation in the composite. Fracture toughnesstesting using a modified double cantilever beam method with in situ observation of crack prop-agation in a scanning electron microscope shows that the composite with the strengthenedinterface has a more desirable R-curve behaviour and a higher fracture toughness value than thenormal composite.
文摘The effects of ternary solutes Ti, Co, V, Cr, Ta, W and Mo on the D03 phase 5tability of Fe3Alintermetallics are investigated by tight-binding linear Muffin-tin orbitaI method. The predictedsite preference5 of these elements in Fe3AI are in agreement with the experimental observations.The calculated Iocal magnetic moment of Fe3AI is identical to the experimentaI. ln addition, itis found that the D03 phase stability of Fe3AI doped with Ti, V, Co and Cr depends on 'energygap- of energy band near Fermi level. while the D03 phase stability of Fe3AI doped with Ta, Wand Mo may be affected by Madelung energy.
文摘By use of self-consistent field Xα scattered-wave (SCF-Xα-SW) method, the electronic structure was calculated for four models of Ti4Al14X (X=Al, Fe, Ni and Cu) clusters. The Ti4Al14X cluster was developed based on L12 Al3Ti-base intermetallic compound. The results are presented using the density of states (DOS) and one-electron properties, such as relative binding tendency between the atom and the model cluster, and hybrid bonding tendency between the alloying element and the host atoms. By comparing the four models of Ti4Al14X cluster, the effect of the Fe, Ni or Cu atom on the physical properties of Al3Ti-based L12 intermetallic compounds is analyzed. The results indicate that the addition of the Fe, Ni or Cu atom intensifies the relative binding tendency between Ti atom and Ti4Al14X cluster. It was found that the Fermi level (EF) lies in a maximum in the DOS for Ti4Al14Al cluster; on the contrary, the EF comes near a minimum tn the DOS for Ti4Al14X (X=Fe, Ni and Cu) cluster. Thus the L12 crystal structure for binary Al3Ti alloy is unstable, and the addition of the Fe, Ni or Cu atom to Al3Ti is benefical to stabilize L12 crystal structure. The calculation also shows that the Fe, Ni or Cu atom strengthens the hybrid bonding tendency between the central atom and the host atoms for Ti4Al14X cluster and thereby may lead to the constriction of the lattice of Al3Ti-base intermetallic compounds.
文摘MAKAROV and Trontelj first reported the WO<sub>3</sub>-based low voltage varistor material doped with MnO<sub>2</sub> and Na<sub>2</sub>CO<sub>3</sub> in 1994. This material is worth further study because of its low threshold voltage （ 【 10 V/mm）. We have found that the doping of Co<sub>2</sub>O<sub>3</sub> can obviously improve the nonlinearity of WO<sub>3</sub>-MnO<sub>2</sub>-Na<sub>2</sub>CO<sub>3</sub> series with nonlinear coefficient α≈ 2,and a may be higher than 5 when the amount of Co<sub>2</sub>O<sub>3</sub> is 1% （mole percentage）. However, the nonlinear characteristic almost vanished when 0.5% Al<sub>2</sub>O<sub>3</sub> was doped into this system at room temperature, and Al<sub>2</sub>O<sub>3</sub> showed very stable
基金supported by the National Natural Science Foundation of China under Grant Nos. 50705038and 50735001
文摘We address the effects of processing parameters on residual stresses and fatigue properties of LY2 Al alloy by laser shock processing （LSP）. Results show that compressive residual stresses are generated near the surface of samples due to LSP. The maximum compressive residual stress at the surface by two LSP impacts on one side is higher than that by one LSP impact. The maximum value of tensile residual stress is found at the mid-plane of samples subjected to two-sided LSP. Compared with fatigue lives of samples treated by single-sided LSP, lives of those treated by two-sided LSP are lower. However, these are higher than untreated ones.
