Fe-based amorphous alloys with ductility were synthesized using the commercial cast iron QT50 (denoted as QT) with the combining minor addition of B and Al by single roller melt-spinning. The melt-spun (QT1-xBx)99Al1 ...Fe-based amorphous alloys with ductility were synthesized using the commercial cast iron QT50 (denoted as QT) with the combining minor addition of B and Al by single roller melt-spinning. The melt-spun (QT1-xBx)99Al1 (x is from 0.006wt% to 0.01wt%) amorphous alloys exhibit onset crystallization temperatures and Curie temperatures of 759-780 and 629-642 K respectively, and whi- ch increase with B content. The amorphous ribbons are ductile and can be bent 180° without breaking. With the increase in B content from 0.006wt% to 0.01wt%, the Vickers microhardness of the amorphous alloys increases from Hv 830 to Hv 1110. The effects of the additional B and Al elements on the glass forming ability and mechanical properties were also discussed.展开更多
The addition of early transition metals(ETMs) into Fe-based amorphous alloys is practically found to be effective in reducing the α-Fe grain size in crystallization process. In this paper, by using ab initio molecu...The addition of early transition metals(ETMs) into Fe-based amorphous alloys is practically found to be effective in reducing the α-Fe grain size in crystallization process. In this paper, by using ab initio molecular dynamics simulations, the mechanism of the effect of two typical ETMs(Nb and W) on nano-crystallization is studied. It is found that the diffusion ability in amorphous alloy is mainly determined by the bonding energy of the atom rather than the size or weight of the atom. The alloying of B dramatically reduces the diffusion ability of the ETM atoms, which prevents the supply of Fe near the grain surface and consequently suppresses the growth of α-Fe grains. Moreover, the difference in grain refining effectiveness between Nb and W could be attributed to the larger bonding energy between Nb and B than that between W and B.展开更多
To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of CuaTTi34Zr11Nis and Cu47Ti34Zr11Ni8+20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by las...To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of CuaTTi34Zr11Nis and Cu47Ti34Zr11Ni8+20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by laser cladding, respectively. SEM (scanning electron microscopy), EDS (energy dispersive X-ray spectroscopy), XRD (X-ray diffraction) and TEM (transmission electron microscopy) techniques were employed to study the phases of the coatings. The results show that the coatings mainly consist of amorphous phase and different intermetallic compounds. The reason of formation of amorphous phase and the function of SiC particles were explained in details.展开更多
传播电子显微镜学(TEM ) 通常被用来识别 theamorphicity。然而,一些人工制品可以由于不适当的 TEM 陪衬准备被介绍。在这篇论文,有或没有玻璃转化的三副 Al 富有的金属性的眼镜为在 TEMspecimen 准备期间在同样熄灭的结构上描绘电刷...传播电子显微镜学(TEM ) 通常被用来识别 theamorphicity。然而,一些人工制品可以由于不适当的 TEM 陪衬准备被介绍。在这篇论文,有或没有玻璃转化的三副 Al 富有的金属性的眼镜为在 TEMspecimen 准备期间在同样熄灭的结构上描绘电刷光条件的效果被选择。调制明亮黑暗的结构 underTEM 观察的出现对电刷光条件密切敏感,这被显示出,它建议我们当在 TEM 下面检验非结晶的合金时,对可能的人工制品小心由标本准备导致了。展开更多
Microstructures and magnetic properties of Fe84Nb7B9,Fe80Ti8B 12 and Fe32Ni36(Nb/V)7Si8B17 powders and their bulk alloys prepared by mechanical alloying(MA) method and hot-press sintering were studied. The results...Microstructures and magnetic properties of Fe84Nb7B9,Fe80Ti8B 12 and Fe32Ni36(Nb/V)7Si8B17 powders and their bulk alloys prepared by mechanical alloying(MA) method and hot-press sintering were studied. The results show that: 1) After MA for 20 h,nanocrystalline bcc singl e phase supersaturated solid solution forms in Fe84-Nb7B9 and Fe8 0Ti8B12 alloys,amorphous structure forms in Fe32Ni36Nb7 Si8B17 alloy,duplex microstructure composed of nanocrystalline γ- (FeNi) supersaturated solid solution and trace content of Fe2B phase forms in Fe32Ni36-V7Si8B17 alloy. 2) The decomposition process of supersaturated solid solution phases in Fe84Nb7B9 and Fe80Ti8B 12 alloys happens at 710780 ℃,crystallization reaction in Fe (32)Ni36Nb7Si8B17 alloy happens at 530 ℃(the temperature of peak value) and residual amorphous crystallized further happens at 760 ℃ (the temperature of peak value),phase decomposition process of supersaturated solid solution at 780 ℃ (the temperature of peak value) and crystallization reaction at 431 ℃ (the temperature of peak value) happens in Fe32Ni36V7S i8B17 alloy. 3) under 900 ℃,30 MPa,(0.5 h) hot-press sintering conditions,bulk alloys with high relative density(94.7%95.8%) can be ob tained. Except that the grain size of Fe84Nb7B9 bulk alloy is large,s uperfine grains (grain size 50200 nm) are obtained in other alloys. Exc ept that single phase microstructure is obtained in Fe80Ti8B12 bul k alloy,multi-phase microstructures are obtained in other alloys. 4) The magne tic properties of Fe80Ti8B12bulk alloy(Bs=1.74 T,Hc= 4.35 kA/m) are significantly superior to those of other bulk alloys,which is r elated to the different phases of nanocrystalline or amorphous powder formed dur ing hot-press sintering process and grain size.展开更多
Bulk Zr55Al10Ni5Cu30 metallic glass plates with a dimension of 85 mm×35mm×4 mm and a complicated plate were fabricated by injecting casting method using spongy zirconium and industrial purity aluminum, nicke...Bulk Zr55Al10Ni5Cu30 metallic glass plates with a dimension of 85 mm×35mm×4 mm and a complicated plate were fabricated by injecting casting method using spongy zirconium and industrial purity aluminum, nickel and copper as raw materials. It was shown that the holding time of liquid metals at elevated temperatures had a great influence on the oxygen content of the plates due to the contamination resulting from the atmosphere. Increasing holding time resulted in the increase of oxygen content in the injected alloy. The glass transition temperatures of the bulk metallic glass plates are higher than that reported in the literature and crystallization temperature is lower for the one with higher oxygen content at the same heating rate. The extension of the undercooled liquid region △Tx reaching about 87 K is 3 K higher than that previously reported and 26 K higher than that with oxygen content of 0.076 wt pct for the one with oxygen content as high as 0.065 wt pct. Therefore the oxygen content of the alloy has a significant influence on the glass forming ability and thermal stability of bulk metal glass. It is suggested that direct correlation between high glass forming ability and large △Tx is only valid for a well-defined low oxygen concentration or has to be reconsidered by incorporating oxygen as an additional alloying element.展开更多
An inflection hehaviour was revealed during isothermal annealing under the observation of transition of the coercivity of Fe-Si-B amorphous alloys during local crystallization.It may be interpreted by the transition ...An inflection hehaviour was revealed during isothermal annealing under the observation of transition of the coercivity of Fe-Si-B amorphous alloys during local crystallization.It may be interpreted by the transition of α-Fe grain precipitated from single to multiple domain, Thus,the theoretical expression of H_0-t_a may be derived.The plot of expression H_0-t_a calcu- lated well represents the feature of the experimental curve.展开更多
The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction (XRD), differential scanning calorimeter (DSC), and transmission...The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction (XRD), differential scanning calorimeter (DSC), and transmission electron microscopy (TEM).The results indicated that the as-cast Nd60Fe20Al10Ni10-xYx(X=-0, 2) amorphous alloys were fabricated with some quenched-in crystals, which could be restrained by Y. With the effect of yttrium, both the crystallization temperature and exothermic peak shifted to higher temperatures, illustrating that the thermal stability could be improved. The addition of Y changed the crystallization process and final crystallization results. Moreover, the crystallites in the amorphous matrix became more homogeneous and smaller. Meanwhile, Y was useful for the passivation of oxygen in chemistry and restrained the negative effect of oxygen. The activation energies of the start of crystallization and peaking were 1.21 and 1.16 eV, respectively, according to the Kissinger equation.展开更多
The effects of Ta addition on the microstructure and mechanical properties of Ti40Zr25Ni8Cu9Be18 bulk amorphous alloy were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM), scan el...The effects of Ta addition on the microstructure and mechanical properties of Ti40Zr25Ni8Cu9Be18 bulk amorphous alloy were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM), scan electron microscopy (SEM) and compressive testing. As a result, the addition of Ta (0-8at%) prompted the successive precipitation of quasicrystalline phase, CuTi2 phase and bcc β-Ti solid solution. Additionally, the addition of less Ta content (3at%-5at%) led to the formation of amorphous ma- trix/nanoquasicrystal/CuTi2 complex phase structure; and nanoquasicrystals, as reinforcement precipitates, improved the fracture strength of Ti-Zr-Ni-Cu-Be-Ta alloys, which led to the high compressive fracture strength 1856 MPa of Ta5 alloy. With increasing Ta content (5at%-8at%), although the ductile dendritic β-Ti solid solution was precipitated, the strength and plasticity decreased to a great extent resulting from the growth of quasicrystalline phase and CuTi2 phase.展开更多
Acoustic-frequency induction melting together with rapid quenching was used to prepare Mg65Cu25Y10 bulk amorphous alloy containing primary crystalline phases. Transmission electron microscopy(TEM),X-ray diffractometry...Acoustic-frequency induction melting together with rapid quenching was used to prepare Mg65Cu25Y10 bulk amorphous alloy containing primary crystalline phases. Transmission electron microscopy(TEM),X-ray diffractometry(XRD),environmental scanning electron microscopy(ESEM) and atomic force microscopy(AFM) were used to study the amorphization and morphology of the prepared alloy. Under micro condition,the sample alloy is composed of amorphous structure with cauliflorate shape,primary CuMg2 dendrite phase,mixed primary CuMg2 and Cu2Y crystalline phases,as well as Mg phase with small size. Further study under sub-micro condition shows that,the planar amorphous structure of cauliflorate shape is composed of the three-dimensional sub-micro morphology of "bulge-concavity" pattern,which extends into the space in terms of certain period. It is estimated that the major factors influencing the micro and sub-micro morphologies of amorphous alloy are its super-cooling liquid structure,rapid quenching transformation,as well as the melting conditions.展开更多
With processes of arc melting, inductive melting and copper mold suction casting, a plate Fe-based bulk amorphous alloy Fe_(60)Co_8Zr_(10)Mo_5W_2B_(15) with a thickness of 1mm was prepared. The surfaces and fractures ...With processes of arc melting, inductive melting and copper mold suction casting, a plate Fe-based bulk amorphous alloy Fe_(60)Co_8Zr_(10)Mo_5W_2B_(15) with a thickness of 1mm was prepared. The surfaces and fractures of the cast bulk amorphous alloy were agleam and with typical metallic luster. The glass transition temperature(T_g), supercooled liquid region(△T_x)and reduced glass transition temperature(T_(rg))of the prepared Fe-based amorphous alloy are 884 K,63 K, and 0.611 respectively. The fracture toughness of the cast bulk amorphous alloy is at the level of 1.6 MPa·m^(1/2).展开更多
The thermal stability of milling Fe86Zr11-xNbxB3(x=5.5, 6) melt-spun strip powders and the influence of high-pressure sintering conditions on phase component and grain size of bulk alloys were investigated by X-ray ...The thermal stability of milling Fe86Zr11-xNbxB3(x=5.5, 6) melt-spun strip powders and the influence of high-pressure sintering conditions on phase component and grain size of bulk alloys were investigated by X-ray diffractometry(XRD), differential scanning calorimetry(DSC) and scanning electron microscopy(SEM). The results show that milling melt-spun powder remains in the amorphous state, and the crystallization temperature of which is 480530℃, the apparent activation energy Ep of crystallization process is 294.1219.5kJ/mol. The increasing Nb content can increase crystallization temperature and decrease Ep. Under the sintering conditions of 5.5GPa/3min, when Pw is 1150W, single phase α-Fe nanocrystalline (20.626.7nm) bulk alloy with relative density higher than 99.0% can be obtained. Under the sintering conditions of 5.5GPa/1150W/3min, the magnetic properties of these nanocrystalline bulk alloys are Fe86Zr5.5Nb5.5B3 alloy, Bs=1.15T, Hc=5.08kA·m-1; Fe86Zr5Nb6B3 alloy, Bs=1.26T, Hc=4.27kA·m-1.展开更多
The microstructures and mechanical properties of Als9 GdTNi3Fe alloy extruded from its amorphous powder were investigated at different temperatures. Devitrification process of amorphous phase was also analyzed. As a r...The microstructures and mechanical properties of Als9 GdTNi3Fe alloy extruded from its amorphous powder were investigated at different temperatures. Devitrification process of amorphous phase was also analyzed. As a result, the microstructure of the extruded alloy consists of fee α-Al, binary intermetallic Al3Gd and ternary intermetallic r l phase. The grain size of α-Al is fine. The intermetallic Al3Gd exists as equiaxed particle and τ1 phase appears rod like.展开更多
The melt spun ribbons of Al-La-Y-Ni(Fe)quaternary alloys were prepared by a single- roller melt spinning technique in vacuum.Their amorphous nature,mechanical properties and tensile fracture surface morphology were in...The melt spun ribbons of Al-La-Y-Ni(Fe)quaternary alloys were prepared by a single- roller melt spinning technique in vacuum.Their amorphous nature,mechanical properties and tensile fracture surface morphology were investigated.The experimental results show that amorphous alloys with high strength and good ductility as well as good thermal stability can be achieved in Al-La-Y-Ni(Fe)system,when the alloy contains 85—90 at.-% Al and less than 10 at.-% La+Y.The maximum tensile fracture strength(σ_f) and microhardness(HV)are as high as 760 MPa and 294 DPN,respectively.The as- quenched ribbons can be bent 180 degree without fracturing.The dominant factors for formation of amorphous Al-La-Y-Ni(Fe)are the strong attractive interaction among Al, La,Y and a decrease of melting temperature.展开更多
The hydrogenation/dehydrogenation thermodynamic properties of a Mg 50 Ni 50 alloy synthesized by mechanical alloying is measured by electrochemical method, and serious hydrogenation/dehydrogenation hysteresis...The hydrogenation/dehydrogenation thermodynamic properties of a Mg 50 Ni 50 alloy synthesized by mechanical alloying is measured by electrochemical method, and serious hydrogenation/dehydrogenation hysteresis characteristic was observed. The electrochemical impedance of the electrode discharge reaction of this electrode is mainly composed of charge transfer resistance R ct , hydrogen diffusion impedance Z w and surface H adsorption/desorption capacitance C ads . Electrochemical impedance analysis reveals that R ct is about one degree larger than the other impedance component. Thus it is reasonable to believe that discharge reaction is mainly dominated by the charge transfer reaction at the alloy surface, and the discharge hysteresis phenomenon is related to the factors that effect the charge transfer reaction. Hydroxides are present in the alloy surface before and after charging/discharging. These hydroxides would decrease the conductivity of the alloy surface and hinder the charge transfer process.展开更多
Ti/Cr (atomic ratio 3:4) amorphous alloy was prepared by ball milling the rapidly quenched Ti/Cr ribbons for 30h, and then milled with MgH_2 for 50 h under Ar atmosphere to obtain MgH_2-30wt. % Ti/Cr composite. The XR...Ti/Cr (atomic ratio 3:4) amorphous alloy was prepared by ball milling the rapidly quenched Ti/Cr ribbons for 30h, and then milled with MgH_2 for 50 h under Ar atmosphere to obtain MgH_2-30wt. % Ti/Cr composite. The XRD results indicate that MgH_2 decomposed partly during ball milling process. The brittle MgH_2 and the mechanical driving force resulted in a highly dispersive distribution of the Ti/Cr amorphous phase in the Mg matrix. The favorable hydrogenation performance is mainly attributed to the com...展开更多
A set of fracture device was designed on the basis of traditional scratching-electrode technology and used to study the passivation process of two magnetron-sputtered stainless sleel coatings (amorphous and crystallin...A set of fracture device was designed on the basis of traditional scratching-electrode technology and used to study the passivation process of two magnetron-sputtered stainless sleel coatings (amorphous and crystalline struture). The results of fracture tests in 3.5 % NaCl aqueous solution show that the amorphous alloy has a high bare surface reactivity and a high passive rate in comparison with the crystalline alloy. The effect of structure on corrosion resistance is also discussed. The excellent corrosion resistance of amorphous alloy is considered to be partly attributed to its great passivation ability.展开更多
基金This work was financially supported by the National Natural Science Foundation of China (No.50225103, 50471001 and 50631010).
文摘Fe-based amorphous alloys with ductility were synthesized using the commercial cast iron QT50 (denoted as QT) with the combining minor addition of B and Al by single roller melt-spinning. The melt-spun (QT1-xBx)99Al1 (x is from 0.006wt% to 0.01wt%) amorphous alloys exhibit onset crystallization temperatures and Curie temperatures of 759-780 and 629-642 K respectively, and whi- ch increase with B content. The amorphous ribbons are ductile and can be bent 180° without breaking. With the increase in B content from 0.006wt% to 0.01wt%, the Vickers microhardness of the amorphous alloys increases from Hv 830 to Hv 1110. The effects of the additional B and Al elements on the glass forming ability and mechanical properties were also discussed.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB0300502)the Shenzhen Municipal Fundamental Science and Technology Research Program,China(Grant No.JCYJ20170815162201821)the Fundamental Research Funds for Central Universities,China(Grant No.31020170QD102)
文摘The addition of early transition metals(ETMs) into Fe-based amorphous alloys is practically found to be effective in reducing the α-Fe grain size in crystallization process. In this paper, by using ab initio molecular dynamics simulations, the mechanism of the effect of two typical ETMs(Nb and W) on nano-crystallization is studied. It is found that the diffusion ability in amorphous alloy is mainly determined by the bonding energy of the atom rather than the size or weight of the atom. The alloying of B dramatically reduces the diffusion ability of the ETM atoms, which prevents the supply of Fe near the grain surface and consequently suppresses the growth of α-Fe grains. Moreover, the difference in grain refining effectiveness between Nb and W could be attributed to the larger bonding energy between Nb and B than that between W and B.
基金supported by the Open Fund of the State Key Laboratory of Advanced Welding Production Technology in Harbin Institute of Technology,Chinathe Open Fund of the State Key Laboratory of Materials Processing and Die&Mould Technology in Huazhong University of Science and Technology,China
文摘To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of CuaTTi34Zr11Nis and Cu47Ti34Zr11Ni8+20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by laser cladding, respectively. SEM (scanning electron microscopy), EDS (energy dispersive X-ray spectroscopy), XRD (X-ray diffraction) and TEM (transmission electron microscopy) techniques were employed to study the phases of the coatings. The results show that the coatings mainly consist of amorphous phase and different intermetallic compounds. The reason of formation of amorphous phase and the function of SiC particles were explained in details.
基金This work was financially supported by the National Natural Science Foundation of China (Nos. 50271070, 50323009, 50471076).
文摘传播电子显微镜学(TEM ) 通常被用来识别 theamorphicity。然而,一些人工制品可以由于不适当的 TEM 陪衬准备被介绍。在这篇论文,有或没有玻璃转化的三副 Al 富有的金属性的眼镜为在 TEMspecimen 准备期间在同样熄灭的结构上描绘电刷光条件的效果被选择。调制明亮黑暗的结构 underTEM 观察的出现对电刷光条件密切敏感,这被显示出,它建议我们当在 TEM 下面检验非结晶的合金时,对可能的人工制品小心由标本准备导致了。
文摘Microstructures and magnetic properties of Fe84Nb7B9,Fe80Ti8B 12 and Fe32Ni36(Nb/V)7Si8B17 powders and their bulk alloys prepared by mechanical alloying(MA) method and hot-press sintering were studied. The results show that: 1) After MA for 20 h,nanocrystalline bcc singl e phase supersaturated solid solution forms in Fe84-Nb7B9 and Fe8 0Ti8B12 alloys,amorphous structure forms in Fe32Ni36Nb7 Si8B17 alloy,duplex microstructure composed of nanocrystalline γ- (FeNi) supersaturated solid solution and trace content of Fe2B phase forms in Fe32Ni36-V7Si8B17 alloy. 2) The decomposition process of supersaturated solid solution phases in Fe84Nb7B9 and Fe80Ti8B 12 alloys happens at 710780 ℃,crystallization reaction in Fe (32)Ni36Nb7Si8B17 alloy happens at 530 ℃(the temperature of peak value) and residual amorphous crystallized further happens at 760 ℃ (the temperature of peak value),phase decomposition process of supersaturated solid solution at 780 ℃ (the temperature of peak value) and crystallization reaction at 431 ℃ (the temperature of peak value) happens in Fe32Ni36V7S i8B17 alloy. 3) under 900 ℃,30 MPa,(0.5 h) hot-press sintering conditions,bulk alloys with high relative density(94.7%95.8%) can be ob tained. Except that the grain size of Fe84Nb7B9 bulk alloy is large,s uperfine grains (grain size 50200 nm) are obtained in other alloys. Exc ept that single phase microstructure is obtained in Fe80Ti8B12 bul k alloy,multi-phase microstructures are obtained in other alloys. 4) The magne tic properties of Fe80Ti8B12bulk alloy(Bs=1.74 T,Hc= 4.35 kA/m) are significantly superior to those of other bulk alloys,which is r elated to the different phases of nanocrystalline or amorphous powder formed dur ing hot-press sintering process and grain size.
基金supported by the National 863 projects by the Department of Science and Technology of China (No. 2002AA331080)the Program of Beijing Significant Science and Technology Project (No.020420050021)
文摘Bulk Zr55Al10Ni5Cu30 metallic glass plates with a dimension of 85 mm×35mm×4 mm and a complicated plate were fabricated by injecting casting method using spongy zirconium and industrial purity aluminum, nickel and copper as raw materials. It was shown that the holding time of liquid metals at elevated temperatures had a great influence on the oxygen content of the plates due to the contamination resulting from the atmosphere. Increasing holding time resulted in the increase of oxygen content in the injected alloy. The glass transition temperatures of the bulk metallic glass plates are higher than that reported in the literature and crystallization temperature is lower for the one with higher oxygen content at the same heating rate. The extension of the undercooled liquid region △Tx reaching about 87 K is 3 K higher than that previously reported and 26 K higher than that with oxygen content of 0.076 wt pct for the one with oxygen content as high as 0.065 wt pct. Therefore the oxygen content of the alloy has a significant influence on the glass forming ability and thermal stability of bulk metal glass. It is suggested that direct correlation between high glass forming ability and large △Tx is only valid for a well-defined low oxygen concentration or has to be reconsidered by incorporating oxygen as an additional alloying element.
文摘An inflection hehaviour was revealed during isothermal annealing under the observation of transition of the coercivity of Fe-Si-B amorphous alloys during local crystallization.It may be interpreted by the transition of α-Fe grain precipitated from single to multiple domain, Thus,the theoretical expression of H_0-t_a may be derived.The plot of expression H_0-t_a calcu- lated well represents the feature of the experimental curve.
基金the National Natural Science Foundation of China (50571052)
文摘The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction (XRD), differential scanning calorimeter (DSC), and transmission electron microscopy (TEM).The results indicated that the as-cast Nd60Fe20Al10Ni10-xYx(X=-0, 2) amorphous alloys were fabricated with some quenched-in crystals, which could be restrained by Y. With the effect of yttrium, both the crystallization temperature and exothermic peak shifted to higher temperatures, illustrating that the thermal stability could be improved. The addition of Y changed the crystallization process and final crystallization results. Moreover, the crystallites in the amorphous matrix became more homogeneous and smaller. Meanwhile, Y was useful for the passivation of oxygen in chemistry and restrained the negative effect of oxygen. The activation energies of the start of crystallization and peaking were 1.21 and 1.16 eV, respectively, according to the Kissinger equation.
基金This work was financially supported by the New Century Excellent Person Supporting Project, Science and Technology Foundation of Shaanxi Province of China, DPOP and Young Science and Technology Foundation in NWPU.
文摘The effects of Ta addition on the microstructure and mechanical properties of Ti40Zr25Ni8Cu9Be18 bulk amorphous alloy were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM), scan electron microscopy (SEM) and compressive testing. As a result, the addition of Ta (0-8at%) prompted the successive precipitation of quasicrystalline phase, CuTi2 phase and bcc β-Ti solid solution. Additionally, the addition of less Ta content (3at%-5at%) led to the formation of amorphous ma- trix/nanoquasicrystal/CuTi2 complex phase structure; and nanoquasicrystals, as reinforcement precipitates, improved the fracture strength of Ti-Zr-Ni-Cu-Be-Ta alloys, which led to the high compressive fracture strength 1856 MPa of Ta5 alloy. With increasing Ta content (5at%-8at%), although the ductile dendritic β-Ti solid solution was precipitated, the strength and plasticity decreased to a great extent resulting from the growth of quasicrystalline phase and CuTi2 phase.
基金Projects(0552nm028 04DZ05616) supported by Shanghai Science and Technology Committee, China
文摘Acoustic-frequency induction melting together with rapid quenching was used to prepare Mg65Cu25Y10 bulk amorphous alloy containing primary crystalline phases. Transmission electron microscopy(TEM),X-ray diffractometry(XRD),environmental scanning electron microscopy(ESEM) and atomic force microscopy(AFM) were used to study the amorphization and morphology of the prepared alloy. Under micro condition,the sample alloy is composed of amorphous structure with cauliflorate shape,primary CuMg2 dendrite phase,mixed primary CuMg2 and Cu2Y crystalline phases,as well as Mg phase with small size. Further study under sub-micro condition shows that,the planar amorphous structure of cauliflorate shape is composed of the three-dimensional sub-micro morphology of "bulge-concavity" pattern,which extends into the space in terms of certain period. It is estimated that the major factors influencing the micro and sub-micro morphologies of amorphous alloy are its super-cooling liquid structure,rapid quenching transformation,as well as the melting conditions.
文摘With processes of arc melting, inductive melting and copper mold suction casting, a plate Fe-based bulk amorphous alloy Fe_(60)Co_8Zr_(10)Mo_5W_2B_(15) with a thickness of 1mm was prepared. The surfaces and fractures of the cast bulk amorphous alloy were agleam and with typical metallic luster. The glass transition temperature(T_g), supercooled liquid region(△T_x)and reduced glass transition temperature(T_(rg))of the prepared Fe-based amorphous alloy are 884 K,63 K, and 0.611 respectively. The fracture toughness of the cast bulk amorphous alloy is at the level of 1.6 MPa·m^(1/2).
基金Project(0452NM086) supported by the Tackling Key Science and Technology Programof Shanghai , China
文摘The thermal stability of milling Fe86Zr11-xNbxB3(x=5.5, 6) melt-spun strip powders and the influence of high-pressure sintering conditions on phase component and grain size of bulk alloys were investigated by X-ray diffractometry(XRD), differential scanning calorimetry(DSC) and scanning electron microscopy(SEM). The results show that milling melt-spun powder remains in the amorphous state, and the crystallization temperature of which is 480530℃, the apparent activation energy Ep of crystallization process is 294.1219.5kJ/mol. The increasing Nb content can increase crystallization temperature and decrease Ep. Under the sintering conditions of 5.5GPa/3min, when Pw is 1150W, single phase α-Fe nanocrystalline (20.626.7nm) bulk alloy with relative density higher than 99.0% can be obtained. Under the sintering conditions of 5.5GPa/1150W/3min, the magnetic properties of these nanocrystalline bulk alloys are Fe86Zr5.5Nb5.5B3 alloy, Bs=1.15T, Hc=5.08kA·m-1; Fe86Zr5Nb6B3 alloy, Bs=1.26T, Hc=4.27kA·m-1.
文摘The microstructures and mechanical properties of Als9 GdTNi3Fe alloy extruded from its amorphous powder were investigated at different temperatures. Devitrification process of amorphous phase was also analyzed. As a result, the microstructure of the extruded alloy consists of fee α-Al, binary intermetallic Al3Gd and ternary intermetallic r l phase. The grain size of α-Al is fine. The intermetallic Al3Gd exists as equiaxed particle and τ1 phase appears rod like.
文摘The melt spun ribbons of Al-La-Y-Ni(Fe)quaternary alloys were prepared by a single- roller melt spinning technique in vacuum.Their amorphous nature,mechanical properties and tensile fracture surface morphology were investigated.The experimental results show that amorphous alloys with high strength and good ductility as well as good thermal stability can be achieved in Al-La-Y-Ni(Fe)system,when the alloy contains 85—90 at.-% Al and less than 10 at.-% La+Y.The maximum tensile fracture strength(σ_f) and microhardness(HV)are as high as 760 MPa and 294 DPN,respectively.The as- quenched ribbons can be bent 180 degree without fracturing.The dominant factors for formation of amorphous Al-La-Y-Ni(Fe)are the strong attractive interaction among Al, La,Y and a decrease of melting temperature.
文摘The hydrogenation/dehydrogenation thermodynamic properties of a Mg 50 Ni 50 alloy synthesized by mechanical alloying is measured by electrochemical method, and serious hydrogenation/dehydrogenation hysteresis characteristic was observed. The electrochemical impedance of the electrode discharge reaction of this electrode is mainly composed of charge transfer resistance R ct , hydrogen diffusion impedance Z w and surface H adsorption/desorption capacitance C ads . Electrochemical impedance analysis reveals that R ct is about one degree larger than the other impedance component. Thus it is reasonable to believe that discharge reaction is mainly dominated by the charge transfer reaction at the alloy surface, and the discharge hysteresis phenomenon is related to the factors that effect the charge transfer reaction. Hydroxides are present in the alloy surface before and after charging/discharging. These hydroxides would decrease the conductivity of the alloy surface and hinder the charge transfer process.
基金supported by the Special Funds for Major States Basic Research Project (No. TG20000264-06) of MOST, China
文摘Ti/Cr (atomic ratio 3:4) amorphous alloy was prepared by ball milling the rapidly quenched Ti/Cr ribbons for 30h, and then milled with MgH_2 for 50 h under Ar atmosphere to obtain MgH_2-30wt. % Ti/Cr composite. The XRD results indicate that MgH_2 decomposed partly during ball milling process. The brittle MgH_2 and the mechanical driving force resulted in a highly dispersive distribution of the Ti/Cr amorphous phase in the Mg matrix. The favorable hydrogenation performance is mainly attributed to the com...
文摘A set of fracture device was designed on the basis of traditional scratching-electrode technology and used to study the passivation process of two magnetron-sputtered stainless sleel coatings (amorphous and crystalline struture). The results of fracture tests in 3.5 % NaCl aqueous solution show that the amorphous alloy has a high bare surface reactivity and a high passive rate in comparison with the crystalline alloy. The effect of structure on corrosion resistance is also discussed. The excellent corrosion resistance of amorphous alloy is considered to be partly attributed to its great passivation ability.