In the present work, three-dimensional molecular dynamics simulation is carried out to elucidate the nanoinden- tation behaviors of CuZr Bulk metallic glasses （BMGs）. The substrate indenter system is modeled using h...In the present work, three-dimensional molecular dynamics simulation is carried out to elucidate the nanoinden- tation behaviors of CuZr Bulk metallic glasses （BMGs）. The substrate indenter system is modeled using hybrid interatomic potentials including both many-body Finnis Sinclair （FS） and two-body Morse potentials. A spherical rigid indenter （diameter= 60 A（1 A = 10 ^-10 m）） is employed to simulate the indentation process. Three samples of BMGs including Cu25Zr75, CusoZr50, and Cu75Zr25 are designed and the metallic glasses are formed by rapid cooling from the melt state at about 2000 K. The radial distribution functions are analyzed to reveal the dynamical evolution of the structure of the atoms with different compositions and different cooling rates. The mechanical behavior can be well understood in terms of load-depth curves and Hardness-depth curves during the nanoindentation process. Our results indicate a positive linear relationship between the hardness and the Cu concentration of the BMG sample. To reveal the importance of cooling rate provided during the processing of BMGs, we investigate the indentation behaviors of CusoZr50 at three different quenching rates. Nanoindentation results and radial distribution function （RDF） curves at room temperature indicate that a sample can be made harder and more stable by slowing down the quenching rate.展开更多
The infiltration casting method is widely employed for the preparation of ex-situ composite materials.However,the production of composite materials using this method must necessitates a comprehensive understanding of ...The infiltration casting method is widely employed for the preparation of ex-situ composite materials.However,the production of composite materials using this method must necessitates a comprehensive understanding of the wettability and interface characteristics between the reinforcing phase and the bulk metallic glasses(BMGs).This work optimized the composition of Zr-based BMGs through microalloying methods,resulting in a new set of Zr-based BMGs with excellent glass-forming ability.Wetting experiments between the Zr-based BMGs melts and W substrates were conducted using the traditional sessile drop method,and the interfaces were characterized utilizing a scanning electron microscope(SEM)equipped with energy dispersive X-ray spectroscopy(EDS).The work demonstrates that the microalloying method substantially enhances the wettability of the Zr-based BMGs melt.Additionally,the incorporation of Nb element impedes the formation of W-Zr phases,but the introduction of Nb element does not alter the extent of interdiffusion between the constituent elements of the amorphous matrix and W element,indicating that the influence of Nb element on the diffusion of individual elements is minute.展开更多
高迁移率族蛋白(high mobility group protein,HMG)是一系列的染色质相关蛋白,广泛存在于真核生物细胞中,含量丰富,因其在聚丙烯酰胺凝胶电泳中的高迁移率而得名.HMG蛋白家族可分为HMGB、HMGA和HMGN三类亚家族,各亚家族有其特征的结构域...高迁移率族蛋白(high mobility group protein,HMG)是一系列的染色质相关蛋白,广泛存在于真核生物细胞中,含量丰富,因其在聚丙烯酰胺凝胶电泳中的高迁移率而得名.HMG蛋白家族可分为HMGB、HMGA和HMGN三类亚家族,各亚家族有其特征的结构域,这些结构域介导了HMG和DNA或染色质相关区域的相互作用.现已发现这些蛋白质具有多种重要生物学功能,其中几乎所有HMG都可以通过修饰、弯曲或改变染色质/DNA的结构,促进各种蛋白质因子形成大分子复合物来调节基因转录.展开更多
The deformation, damage, fracture, plasticity and melting phenomenon induced by shear fracture were investigated and summarized for Zr-, Cu-, Ti- and Mg-based bulk metallic glasses （BMGs） and their composites. The s...The deformation, damage, fracture, plasticity and melting phenomenon induced by shear fracture were investigated and summarized for Zr-, Cu-, Ti- and Mg-based bulk metallic glasses （BMGs） and their composites. The shear fracture angles of these BMG materials often display obvious differences under compression and tension, and follow either the Mohr-Coulomb criterion or the unified tensile fracture criterion. The compressive plasticity of the composites is always higher than the tensile plasticity, leading to a significant inconsistency. The enhanced plasticity of BMG composites containing ductile dendrites compared to monolithic glasses strongly depends on the details of the microstructure of the composites. A deformation and damage mechanism of pseudo-plasticity, related to local cracking, is proposed to explain the inconsistency of plastic deformation under tension and compression. Besides, significant melting on the shear fracture surfaces was observed. It is suggested that melting is a common phenomenon in these materials with high strength and high elastic energy, as it is typical for BMGs and their composites failing under shear fracture. The melting mechanism can be explained by a combined effect of a significant temperature rise in the shear bands and the instantaneous release of the large amount of elastic energy stored in the material.展开更多
The corrosion resistance of Zr-Al-Ni-Cu(Nb) bulk amorphous alloys was systematically investigated. The experimental results show that the corrosion resistance of Zr-based bulk amorphous alloys can not be considered to...The corrosion resistance of Zr-Al-Ni-Cu(Nb) bulk amorphous alloys was systematically investigated. The experimental results show that the corrosion resistance of Zr-based bulk amorphous alloys can not be considered to be excellent at any situation, whereas it is affected by many factors such as the kind of corrosive medium, solution concentration and the alloy composition. It is found that Zr-Al-Ni-Cu bulk amorphous alloys are seriously corroded in HCl solution in comparison with their excellent corrosion resistance at other acid, alkali and salt circumstances for passivating. Its resistance ability against the chlorine ion induced pitting corrosion can be greatly improved by the addition of Nb element.展开更多
The specific heat capacities of Cu60Zr20Hfl0Til0 bulk metallic glass （BMG） and crystallized alloys were measured from 2 to 101 K. The effect of crystallization on the specific heat capacity of the BMG was studied. T...The specific heat capacities of Cu60Zr20Hfl0Til0 bulk metallic glass （BMG） and crystallized alloys were measured from 2 to 101 K. The effect of crystallization on the specific heat capacity of the BMG was studied. The effects of crystallization and the relationship between local modes and boson peak in the BMG were discussed. The specific heat capacity deviates from the simple Debye behaviors, showing the presence of local harmonic modes （Einstein oscillator） in the BMG and the crystallized alloy. Model calculation includes the contribution of one Debye mode and two Einstein modes for the BMG, one Debye mode and one Einstein mode for the crystallized alloy, showing an adequate description of the experimental data.展开更多
Starting from the quaternary Cu47Ti34Zr11Ni8 alloy, the compositional dependence of thermal and elastic properties of Cu-Ti-Zr-Ni alloys was systematically investigated. Quaternary Cu-Ti-Zr-Ni alloys can be cast direc...Starting from the quaternary Cu47Ti34Zr11Ni8 alloy, the compositional dependence of thermal and elastic properties of Cu-Ti-Zr-Ni alloys was systematically investigated. Quaternary Cu-Ti-Zr-Ni alloys can be cast directly from the melt into copper molds to form fully amorphous strips or rods with the thickness of 3-6 mm. The evidence of the amorphous nature of the cast rods was provided by X-ray spectra. The measured glass transition temperature （Tg） and crystallization temperature （Tx） were obtained for the alloys using differential scanning calorimetry （DSC） at the heating rate of 20 K/s. In the results, the differences between the glass temperature and the crystallization temperature （△Tx=Tx-Tg） are measured with values ranging up to 33-55 K. The reduced glass transition temperature （Trg）, which is the ratio of the glass temperature to the liquidus temperature （T3, is often used as an indication of the glass-forming ability of metallic alloys. For the present Cu-Ti-Zr-Ni alloys, this ratio is typically in the range of 0.5838-0.5959, characteristic of metallic alloys with good glass-forming ability. The elastic constants for several selected alloys were measured using ultrasonic methods. The values of the elastic shear modulus, bulk modulus, and Poisson＇s ratio were also given.展开更多
In-situ dendritic reinforced Dy-Fe-Al amorphous matrix composites with a diameter of 3 mm were designed and fabricated by conventional Cu-mold casting method. XRD and SEM analyses were conducted to investigate the mic...In-situ dendritic reinforced Dy-Fe-Al amorphous matrix composites with a diameter of 3 mm were designed and fabricated by conventional Cu-mold casting method. XRD and SEM analyses were conducted to investigate the microstructure, the mechanical properties and the deformation and fracture behaviors of the composites. The forming mechanism and the deformation and fracture mechanism of the composites were discussed. The results indicate that the microstructures of composites consist of metallic glass matrix and α-Dy dendritic phase. The composites exhibit good mechanical properties with compressive fracture strength of 1 063 MPa, which is attributed to the effective bearing-load ability of the α-Dy dendrites and the glassy matrix and the restriction to the expanding of shear bands and cracks of the α-Dy dendrites. The nature of in-situ crystalline phases embedded in the amorphous matrix for in-situ crystallite reinforced Dy-Fe-Al amorphous matrix composites has a more important influence on the mechanical properties, the deformation and fracture behavior of the composites.展开更多
基金supported by the Higher Education Commission (HEC) of Pakistan (Grant No. +923445490402)
文摘In the present work, three-dimensional molecular dynamics simulation is carried out to elucidate the nanoinden- tation behaviors of CuZr Bulk metallic glasses （BMGs）. The substrate indenter system is modeled using hybrid interatomic potentials including both many-body Finnis Sinclair （FS） and two-body Morse potentials. A spherical rigid indenter （diameter= 60 A（1 A = 10 ^-10 m）） is employed to simulate the indentation process. Three samples of BMGs including Cu25Zr75, CusoZr50, and Cu75Zr25 are designed and the metallic glasses are formed by rapid cooling from the melt state at about 2000 K. The radial distribution functions are analyzed to reveal the dynamical evolution of the structure of the atoms with different compositions and different cooling rates. The mechanical behavior can be well understood in terms of load-depth curves and Hardness-depth curves during the nanoindentation process. Our results indicate a positive linear relationship between the hardness and the Cu concentration of the BMG sample. To reveal the importance of cooling rate provided during the processing of BMGs, we investigate the indentation behaviors of CusoZr50 at three different quenching rates. Nanoindentation results and radial distribution function （RDF） curves at room temperature indicate that a sample can be made harder and more stable by slowing down the quenching rate.
基金the support of the China Manned Space Engineering(YYMT1201-EXP08)。
文摘The infiltration casting method is widely employed for the preparation of ex-situ composite materials.However,the production of composite materials using this method must necessitates a comprehensive understanding of the wettability and interface characteristics between the reinforcing phase and the bulk metallic glasses(BMGs).This work optimized the composition of Zr-based BMGs through microalloying methods,resulting in a new set of Zr-based BMGs with excellent glass-forming ability.Wetting experiments between the Zr-based BMGs melts and W substrates were conducted using the traditional sessile drop method,and the interfaces were characterized utilizing a scanning electron microscope(SEM)equipped with energy dispersive X-ray spectroscopy(EDS).The work demonstrates that the microalloying method substantially enhances the wettability of the Zr-based BMGs melt.Additionally,the incorporation of Nb element impedes the formation of W-Zr phases,but the introduction of Nb element does not alter the extent of interdiffusion between the constituent elements of the amorphous matrix and W element,indicating that the influence of Nb element on the diffusion of individual elements is minute.
文摘高迁移率族蛋白(high mobility group protein,HMG)是一系列的染色质相关蛋白,广泛存在于真核生物细胞中,含量丰富,因其在聚丙烯酰胺凝胶电泳中的高迁移率而得名.HMG蛋白家族可分为HMGB、HMGA和HMGN三类亚家族,各亚家族有其特征的结构域,这些结构域介导了HMG和DNA或染色质相关区域的相互作用.现已发现这些蛋白质具有多种重要生物学功能,其中几乎所有HMG都可以通过修饰、弯曲或改变染色质/DNA的结构,促进各种蛋白质因子形成大分子复合物来调节基因转录.
基金financially supported by the National Natural Science Foundation of China(NSFC)under Gtrant No.50401019the“Hun-dred of Talent Project"by Chinese Academy of Sciences+1 种基金National Outstanding Young Scientist Foundation for Z.F.Zhang under Grant No.50625103the financial support of the Alexander-von-Humboldt(AvH)Foundation.
文摘The deformation, damage, fracture, plasticity and melting phenomenon induced by shear fracture were investigated and summarized for Zr-, Cu-, Ti- and Mg-based bulk metallic glasses （BMGs） and their composites. The shear fracture angles of these BMG materials often display obvious differences under compression and tension, and follow either the Mohr-Coulomb criterion or the unified tensile fracture criterion. The compressive plasticity of the composites is always higher than the tensile plasticity, leading to a significant inconsistency. The enhanced plasticity of BMG composites containing ductile dendrites compared to monolithic glasses strongly depends on the details of the microstructure of the composites. A deformation and damage mechanism of pseudo-plasticity, related to local cracking, is proposed to explain the inconsistency of plastic deformation under tension and compression. Besides, significant melting on the shear fracture surfaces was observed. It is suggested that melting is a common phenomenon in these materials with high strength and high elastic energy, as it is typical for BMGs and their composites failing under shear fracture. The melting mechanism can be explained by a combined effect of a significant temperature rise in the shear bands and the instantaneous release of the large amount of elastic energy stored in the material.
文摘The corrosion resistance of Zr-Al-Ni-Cu(Nb) bulk amorphous alloys was systematically investigated. The experimental results show that the corrosion resistance of Zr-based bulk amorphous alloys can not be considered to be excellent at any situation, whereas it is affected by many factors such as the kind of corrosive medium, solution concentration and the alloy composition. It is found that Zr-Al-Ni-Cu bulk amorphous alloys are seriously corroded in HCl solution in comparison with their excellent corrosion resistance at other acid, alkali and salt circumstances for passivating. Its resistance ability against the chlorine ion induced pitting corrosion can be greatly improved by the addition of Nb element.
基金Project(082102230035)supported by the Foundation of Science and Technology Department of Henan Province,China
文摘The specific heat capacities of Cu60Zr20Hfl0Til0 bulk metallic glass （BMG） and crystallized alloys were measured from 2 to 101 K. The effect of crystallization on the specific heat capacity of the BMG was studied. The effects of crystallization and the relationship between local modes and boson peak in the BMG were discussed. The specific heat capacity deviates from the simple Debye behaviors, showing the presence of local harmonic modes （Einstein oscillator） in the BMG and the crystallized alloy. Model calculation includes the contribution of one Debye mode and two Einstein modes for the BMG, one Debye mode and one Einstein mode for the crystallized alloy, showing an adequate description of the experimental data.
文摘Starting from the quaternary Cu47Ti34Zr11Ni8 alloy, the compositional dependence of thermal and elastic properties of Cu-Ti-Zr-Ni alloys was systematically investigated. Quaternary Cu-Ti-Zr-Ni alloys can be cast directly from the melt into copper molds to form fully amorphous strips or rods with the thickness of 3-6 mm. The evidence of the amorphous nature of the cast rods was provided by X-ray spectra. The measured glass transition temperature （Tg） and crystallization temperature （Tx） were obtained for the alloys using differential scanning calorimetry （DSC） at the heating rate of 20 K/s. In the results, the differences between the glass temperature and the crystallization temperature （△Tx=Tx-Tg） are measured with values ranging up to 33-55 K. The reduced glass transition temperature （Trg）, which is the ratio of the glass temperature to the liquidus temperature （T3, is often used as an indication of the glass-forming ability of metallic alloys. For the present Cu-Ti-Zr-Ni alloys, this ratio is typically in the range of 0.5838-0.5959, characteristic of metallic alloys with good glass-forming ability. The elastic constants for several selected alloys were measured using ultrasonic methods. The values of the elastic shear modulus, bulk modulus, and Poisson＇s ratio were also given.
基金Project(20032137) supported by the Natural Science Foundation of Liaoning Province, China
文摘In-situ dendritic reinforced Dy-Fe-Al amorphous matrix composites with a diameter of 3 mm were designed and fabricated by conventional Cu-mold casting method. XRD and SEM analyses were conducted to investigate the microstructure, the mechanical properties and the deformation and fracture behaviors of the composites. The forming mechanism and the deformation and fracture mechanism of the composites were discussed. The results indicate that the microstructures of composites consist of metallic glass matrix and α-Dy dendritic phase. The composites exhibit good mechanical properties with compressive fracture strength of 1 063 MPa, which is attributed to the effective bearing-load ability of the α-Dy dendrites and the glassy matrix and the restriction to the expanding of shear bands and cracks of the α-Dy dendrites. The nature of in-situ crystalline phases embedded in the amorphous matrix for in-situ crystallite reinforced Dy-Fe-Al amorphous matrix composites has a more important influence on the mechanical properties, the deformation and fracture behavior of the composites.
