Zr_~65 Al_~10 Ni_~10 Cu_~15 , Zr_~52.5 Al_~10 Ni_~10 Cu_~15 Be_~12.5 and Zr_~52.5 Al_~10 Ni_~14.6 Cu_~17.9 Ti_5 bulk amorphous alloys were prepared by copper mould casting. The crystallization kinetics was measured by...Zr_~65 Al_~10 Ni_~10 Cu_~15 , Zr_~52.5 Al_~10 Ni_~10 Cu_~15 Be_~12.5 and Zr_~52.5 Al_~10 Ni_~14.6 Cu_~17.9 Ti_5 bulk amorphous alloys were prepared by copper mould casting. The crystallization kinetics was measured by differential scanning calorimeter(DSC) with different heating rates, and the activation energy was calculated using Kissinger equation. The relationship between thermal stability and rate constant of crystallization reaction is discussed on the view of crystallization kinetics, and the effect of small atom Beryllium on thermal stability of bulk amorphous alloys is also studied.展开更多
Crystalline behavior and magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys were investigated by differential scanning calorimeter (DSC), X ray diffraction (XRD) and...Crystalline behavior and magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys were investigated by differential scanning calorimeter (DSC), X ray diffraction (XRD) and the vibrating sample magnetometer (VSM). Neither glass transition nor supercooled liquid region before crystallization was observed for the as cast Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys. The glass forming ability can be improved significantly by the addition of Co. The as cast Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) alloys show hard magnetic behavior. With the addition of Co content, intrinsic coercivity ( i H c) increases while the saturation magnetization( σ s) and remanence ( σ r) decrease. The Curie temperature for the as cast Nd 60 Fe 30- x Al 10 Co x alloys increases from 451 K for x =0 to 468 K for x =10. Some precipitation of crystalline phases does not affect the hard magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) alloys, while the hard magnetic behavior disappears quickly after the alloys being completely crystallized.展开更多
Crystallization kinetics of Fe55-xCrzsMo7B10C4Nbx（x= 0, 3） bulk amorphous alloys were analyzed using X-ray diffraction and differential scanning; calorimetric （DSC） tests. In practice, crystallization and growth m...Crystallization kinetics of Fe55-xCrzsMo7B10C4Nbx（x= 0, 3） bulk amorphous alloys were analyzed using X-ray diffraction and differential scanning; calorimetric （DSC） tests. In practice, crystallization and growth mechanism were evaluated using DSC tests at four different heating rates （10, 20, 30, and 40 K/rain） and kinetic models. Two-step crystallization behavior was observed when Fe55Cr18MOTB16C4 and Fe52Cr18MoTB16C4Nb3 bulk amorphous alloys were annealed, where Fe36Cr12M010 phase was crystallized in the first step of crystallization. Results show that Fe36Cr12Mo10 and Fe3C phases were crystallized in the structures of the alloys after further annealing： process. Activation energy for the crystallization of Fe36Cr12Mozo phase was measured to be 543 kJ/mol in Fe52Cr18MoTB16C4Nb3 alloy and 375 kJ/mol for Fe55Cr18Mo7B16C4 alloy according to Kissinger-Starink model. Moreover, a two-dimensiona nucleation rate was found in Fe52Cr18Mo7B16C4Nb3 diffusion controlled growth mechanism with decreasing alloy whereas a three-dimensional diffusion controlled growth mechanism with decreasing nucleation rate was found in crystallization of Fe36Crz2Mo10 phase during annealing of Fe55Cr18MoTB16C4 alloy. TEM （transmission electron microscopy） observations reveal that crystalline Fe36Cr12M010 phase nucleated in the structures of the alloys in an average size of 10 nm with completely mottled morphology.展开更多
Centimeter-sized Mg65Zn30Ca5 bulk amorphous alloys were fabricated by the spark plasma sintering process from the amorphous powders with a size smaller than 5 la m prepared by ball-milling. The sintered Mg65Zn30Ca5 sa...Centimeter-sized Mg65Zn30Ca5 bulk amorphous alloys were fabricated by the spark plasma sintering process from the amorphous powders with a size smaller than 5 la m prepared by ball-milling. The sintered Mg65Zn30Ca5 samples were in an amorphous state when the spark plasma sintering was performed at a temperature of 383 K under a pressure of 600 MPa. The data of polarization curves presented that the sintered Mg65Zn30Ca5 bulk amorphous alloys exhibited higher corrosion resistance than pure Mg and AZ31B alloy owing to high content of Zn and homogeneous structure. A calcium phosphate compound layer was formed on the sintered Mg65Zn30Ca5 bulk amorphous sample after immersion in Hanks＇ solution, which is effective in improving corrosion resistance and bioactivity. The sintered MgZnCa bulk amorphous alloys with large dimensions broaden the potential application of bulk amorphous alloys in the biomedical fields.展开更多
Electrochemical corrosion and oxidation resistances of Zr 60 Ni 21 Al 19 amorphous alloy were studied. The ternary amorphous alloy exhibits greater positive potential than its crystalline counterpart and 0Cr19Ni9Ti st...Electrochemical corrosion and oxidation resistances of Zr 60 Ni 21 Al 19 amorphous alloy were studied. The ternary amorphous alloy exhibits greater positive potential than its crystalline counterpart and 0Cr19Ni9Ti stainless steel. Its weight loss result measured in 2 mol/L HCl solution is in agreement with the potentiodynamic curve. But there is no obvious difference in the oxidation resistances between Zr 60 Ni 21 Al 19 amorphous and its crystalline alloys. They both exhibit high oxidation resistance.展开更多
Mg65Cu25Y10 bulk amorphous alloy specimens prepared by conventional copper mould method were heated at 200 °C for different time and the phase contents as well as microstructure were studied.The XRD results show ...Mg65Cu25Y10 bulk amorphous alloy specimens prepared by conventional copper mould method were heated at 200 °C for different time and the phase contents as well as microstructure were studied.The XRD results show that the crystallization of Mg65Cu25Y10 bulk amorphous alloy specimen becomes complete as the treating time increases and Mg2Cu,Mg24Y5 and HCP-Mg crystalline phases are found.Snowflake-like morphology is found in different specimens through SEM observation.The EDS patterns show that the composition of the snowflake-like structure is close to that of the as-cast alloy.Laminated structures are observed from the TEM images of the snowflake-like structure.From the electron diffraction patterns,it is seen that the snowflake-like structure is the combination of Mg24Y5 and amorphous matrix.The FCC-Mg phase in the matrix transforms into HCP-Mg during the heat-treating process.展开更多
Research results on the viscous flow deformation behavior of bulk amorphous alloy in different systems are reviewed. The material exhibits an ideal Newtonian fluid at a high temperature. Analytical solution of lamella...Research results on the viscous flow deformation behavior of bulk amorphous alloy in different systems are reviewed. The material exhibits an ideal Newtonian fluid at a high temperature. Analytical solution of lamellar fluid flow behavior is used to discuss the viscous flow behavior of the bulk amorphous alloy in the supercooled liquid state. A material model, which describes such deformation behavior of Mg6oCusoYlo amorphous alloy, is introduced into the finite element method of microformin8 process. Surface feature size was investigated and found not sensitive to the micro formability. Bulk amorphous alloy may possibly be applied to microelectro-mechanical-systems （MEMS） fabrication.展开更多
The effects of quenched-in crystallites on the fracture of bulk amorphous alloys under cyclic loading condition wereinvestigated in this paper. For the fully amorphous alloy and specimen with fine crystallites the fat...The effects of quenched-in crystallites on the fracture of bulk amorphous alloys under cyclic loading condition wereinvestigated in this paper. For the fully amorphous alloy and specimen with fine crystallites the fatigue crack initiationoccurred on the surface. For the specimen with larger crystallites the crack originated from a big broken crystallitenear the surface. The average striation spacing on amorphous area is much larger than that on the crystallite.Crack initiation occurred at the crystallites is due to that the brittle crystallites broke easily under cyclic deformationcondition. The fine crystallites seemed to be protruded from the amorphous matrix and some bulges appeared onthe surface of specimen with fine crystallites under cyclic loading.展开更多
The effect of Pd addition on the glass-forming ability and thermal stability of the Zr55Al10Cu30Ni5-xPdx (x=0, 1, 3, 5 at. pct) alloys upon copper-mold casting has been investigated. The structure, thermal stability a...The effect of Pd addition on the glass-forming ability and thermal stability of the Zr55Al10Cu30Ni5-xPdx (x=0, 1, 3, 5 at. pct) alloys upon copper-mold casting has been investigated. The structure, thermal stability and microstructure were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM), respectively. It was identified that a new bulk amorphous alloy with the larger supercooled liquid region Tx of 100 K is obtained with substituting Ni by 1 at. pct Pd. Furthermore, the origins that thermal stability and GFA change with increasing of Pd have also beer discussed.展开更多
Many amorphous alloys have been developed to date,but the low plasticity has limited their application.To achieve an amorphous alloy with high plasticity,a series of(Ti_(40)Zr_(25)Cu_(9)Ni_(8) Be_(18))_(100-x)TM_(x)(x...Many amorphous alloys have been developed to date,but the low plasticity has limited their application.To achieve an amorphous alloy with high plasticity,a series of(Ti_(40)Zr_(25)Cu_(9)Ni_(8) Be_(18))_(100-x)TM_(x)(x=0,1,2,3,4 at.%,TM=Nb,Y)alloys were designed to study the influence of Nb and Y addition on the plasticity.The amorphous samples were prepared using the vacuum melting and copper mold casting process.The microstructures,glass forming ability and mechanical properties of the alloys were investigated by X-ray diffractometry(XRD),scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HRTEM),depth-sensitive nanoindentation,and uniaxial compressive test.The plasticity of different bulk amorphous alloys was investigated by measuring the plastic deformation energy(PDE)during loading.The relationship between the PDE value and plasticity in bulk amorphous alloys was explored.Results show that Nb addition decreases the PDE value and promotes the generation of multiple shear bands,which significantly increases the fracture strength and plasticity,while the addition of Y element reduces the fracture strength and plastic strain of the alloy.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 structures of the bulk amorphous Zr41Ti14Cu12.5Nil0.0Be22.5 alloy have been analyzed in solid, supercooled liquid and liquid with X-ray diffraction. The first coordination sphere radii and the first coordination n...The structures of the bulk amorphous Zr41Ti14Cu12.5Nil0.0Be22.5 alloy have been analyzed in solid, supercooled liquid and liquid with X-ray diffraction. The first coordination sphere radii and the first coordination numbers are 0.312 um, 11.2 in solid state.10.932 nm, 10.932 in supercooled liquid region and 0.305 urn, 11.296 in liquid state. The structures are the same in different states. But it shows some tendency to crystallizing that the first coordination sphere radius and the first coordination number drop in supercooled liquid region.展开更多
Designing and synthesis of cost effective bulk metallic glasses （BMGs） has been of considerable interest during the last decade so that they can be made commercially viable. Among these, Zr-based BMGs have been repo...Designing and synthesis of cost effective bulk metallic glasses （BMGs） has been of considerable interest during the last decade so that they can be made commercially viable. Among these, Zr-based BMGs have been reported extensively due to their attractive properties, An alloy having composition Zr65Cu18Ni9A18 was designed and synthesized using 2-3 N pure materials by Cu mould casting. The alloy was characterized by X- ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDS） and high temperature differential scanning calorimetry （DSC）. Thermal parameters like supercooled liquid region △Tx, reduced glass transition temperature Trg, γ and δ parameters were evaluated. Mechanical properties like microhardness, nanohardness, elastic modulus and fracture strength were measured. The alloy showed wide supercooled liquid region of 129＋1 K with improved thermal stability. The alloy has considerable fracture strength along with fair amount of ductility.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
In this study,Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloys samples with the same diameter(8 mm)were prepared by using self-designed molds(viz.refractory steel,pure graphite,and copper molds)with differ...In this study,Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloys samples with the same diameter(8 mm)were prepared by using self-designed molds(viz.refractory steel,pure graphite,and copper molds)with different cooling capacities.Moreover,by eliminating the size effect,the effect of the cooling rate on the microstructure and compression deformation behavior of Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloys was investigated.Differentiation of the cooling curves revealed that the instantaneous cooling rates of the alloy melt at the glass transition temperature(Tg)are 45,52,and 64 K·s^(-1) for refractory steel,pure graphite,and copper molds,respectively.X-ray diffraction,differential scanning calorimetry,and highresolution transmission electron microscopy analysis revealed that with the decrease in the cooling rate,trace icosahedral-like atomic clusters and nanocrystals appear in local areas of the amorphous alloy and that the amount of free volume decreases with the increase in the amount of icosahedra-like atomic clusters and nanocrystals.Compression test results revealed that the elastic strain,yield strength,and compressive strength of the amorphous alloy marginally change with the decrease in the cooling rate,while the plastic strain gradually increases.By fitting,the effective size of the vein-like pattern was linearly related to the enthalpy released during structural relaxation and plastic strain,indicating that at a low cooling rate,the trace nanocrystals in the amorphous alloy could not effectively improve its plasticity and that the amount of free volume mainly affects its plasticity.展开更多
文摘Zr_~65 Al_~10 Ni_~10 Cu_~15 , Zr_~52.5 Al_~10 Ni_~10 Cu_~15 Be_~12.5 and Zr_~52.5 Al_~10 Ni_~14.6 Cu_~17.9 Ti_5 bulk amorphous alloys were prepared by copper mould casting. The crystallization kinetics was measured by differential scanning calorimeter(DSC) with different heating rates, and the activation energy was calculated using Kissinger equation. The relationship between thermal stability and rate constant of crystallization reaction is discussed on the view of crystallization kinetics, and the effect of small atom Beryllium on thermal stability of bulk amorphous alloys is also studied.
文摘Crystalline behavior and magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys were investigated by differential scanning calorimeter (DSC), X ray diffraction (XRD) and the vibrating sample magnetometer (VSM). Neither glass transition nor supercooled liquid region before crystallization was observed for the as cast Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys. The glass forming ability can be improved significantly by the addition of Co. The as cast Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) alloys show hard magnetic behavior. With the addition of Co content, intrinsic coercivity ( i H c) increases while the saturation magnetization( σ s) and remanence ( σ r) decrease. The Curie temperature for the as cast Nd 60 Fe 30- x Al 10 Co x alloys increases from 451 K for x =0 to 468 K for x =10. Some precipitation of crystalline phases does not affect the hard magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) alloys, while the hard magnetic behavior disappears quickly after the alloys being completely crystallized.
文摘Crystallization kinetics of Fe55-xCrzsMo7B10C4Nbx（x= 0, 3） bulk amorphous alloys were analyzed using X-ray diffraction and differential scanning; calorimetric （DSC） tests. In practice, crystallization and growth mechanism were evaluated using DSC tests at four different heating rates （10, 20, 30, and 40 K/rain） and kinetic models. Two-step crystallization behavior was observed when Fe55Cr18MOTB16C4 and Fe52Cr18MoTB16C4Nb3 bulk amorphous alloys were annealed, where Fe36Cr12M010 phase was crystallized in the first step of crystallization. Results show that Fe36Cr12Mo10 and Fe3C phases were crystallized in the structures of the alloys after further annealing： process. Activation energy for the crystallization of Fe36Cr12Mozo phase was measured to be 543 kJ/mol in Fe52Cr18MoTB16C4Nb3 alloy and 375 kJ/mol for Fe55Cr18Mo7B16C4 alloy according to Kissinger-Starink model. Moreover, a two-dimensiona nucleation rate was found in Fe52Cr18Mo7B16C4Nb3 diffusion controlled growth mechanism with decreasing alloy whereas a three-dimensional diffusion controlled growth mechanism with decreasing nucleation rate was found in crystallization of Fe36Crz2Mo10 phase during annealing of Fe55Cr18MoTB16C4 alloy. TEM （transmission electron microscopy） observations reveal that crystalline Fe36Cr12M010 phase nucleated in the structures of the alloys in an average size of 10 nm with completely mottled morphology.
基金financially supported by the Natural Science Foundation of China under Grant No. 51301091the Natural Science Foundation of Jiangsu Province Grant No. BK20151536+1 种基金the Fundamental Research Funds for the Central Universities No. AE16001the Advanced Materials Development and Integration of Novel Structured Metallic and Inorganic Materials from the Ministry of Education, Sport, Culture, Science and Technology, Japan
文摘Centimeter-sized Mg65Zn30Ca5 bulk amorphous alloys were fabricated by the spark plasma sintering process from the amorphous powders with a size smaller than 5 la m prepared by ball-milling. The sintered Mg65Zn30Ca5 samples were in an amorphous state when the spark plasma sintering was performed at a temperature of 383 K under a pressure of 600 MPa. The data of polarization curves presented that the sintered Mg65Zn30Ca5 bulk amorphous alloys exhibited higher corrosion resistance than pure Mg and AZ31B alloy owing to high content of Zn and homogeneous structure. A calcium phosphate compound layer was formed on the sintered Mg65Zn30Ca5 bulk amorphous sample after immersion in Hanks＇ solution, which is effective in improving corrosion resistance and bioactivity. The sintered MgZnCa bulk amorphous alloys with large dimensions broaden the potential application of bulk amorphous alloys in the biomedical fields.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50731005, 50821001 and 50774006)the National Basic Research Program of China (Grant No. 2010CB731600)
文摘Electrochemical corrosion and oxidation resistances of Zr 60 Ni 21 Al 19 amorphous alloy were studied. The ternary amorphous alloy exhibits greater positive potential than its crystalline counterpart and 0Cr19Ni9Ti stainless steel. Its weight loss result measured in 2 mol/L HCl solution is in agreement with the potentiodynamic curve. But there is no obvious difference in the oxidation resistances between Zr 60 Ni 21 Al 19 amorphous and its crystalline alloys. They both exhibit high oxidation resistance.
基金Project (2008-04) supported by the Top Talent Plan of Jiangsu University, ChinaProject (10KJA430008) supported by the Natural Science Foundation of Jiangsu Higher Education Institutions,China
文摘Mg65Cu25Y10 bulk amorphous alloy specimens prepared by conventional copper mould method were heated at 200 °C for different time and the phase contents as well as microstructure were studied.The XRD results show that the crystallization of Mg65Cu25Y10 bulk amorphous alloy specimen becomes complete as the treating time increases and Mg2Cu,Mg24Y5 and HCP-Mg crystalline phases are found.Snowflake-like morphology is found in different specimens through SEM observation.The EDS patterns show that the composition of the snowflake-like structure is close to that of the as-cast alloy.Laminated structures are observed from the TEM images of the snowflake-like structure.From the electron diffraction patterns,it is seen that the snowflake-like structure is the combination of Mg24Y5 and amorphous matrix.The FCC-Mg phase in the matrix transforms into HCP-Mg during the heat-treating process.
基金supported by the National Natural Sci-ence Foundation of China under grant No. 50705092.
文摘Research results on the viscous flow deformation behavior of bulk amorphous alloy in different systems are reviewed. The material exhibits an ideal Newtonian fluid at a high temperature. Analytical solution of lamellar fluid flow behavior is used to discuss the viscous flow behavior of the bulk amorphous alloy in the supercooled liquid state. A material model, which describes such deformation behavior of Mg6oCusoYlo amorphous alloy, is introduced into the finite element method of microformin8 process. Surface feature size was investigated and found not sensitive to the micro formability. Bulk amorphous alloy may possibly be applied to microelectro-mechanical-systems （MEMS） fabrication.
基金This work was supported by the National Key Project for Basic Research under grant No. G2000067201 National Development Project for High Technology under Grant No. 2001AA331010.
文摘The effects of quenched-in crystallites on the fracture of bulk amorphous alloys under cyclic loading condition wereinvestigated in this paper. For the fully amorphous alloy and specimen with fine crystallites the fatigue crack initiationoccurred on the surface. For the specimen with larger crystallites the crack originated from a big broken crystallitenear the surface. The average striation spacing on amorphous area is much larger than that on the crystallite.Crack initiation occurred at the crystallites is due to that the brittle crystallites broke easily under cyclic deformationcondition. The fine crystallites seemed to be protruded from the amorphous matrix and some bulges appeared onthe surface of specimen with fine crystallites under cyclic loading.
基金The authors are grateful to the financial support by the National Key Basic Research and Development Program of China(No.G200067201)National High Technical Research Development Program of China(No.2001AA331010)for this research.
文摘The effect of Pd addition on the glass-forming ability and thermal stability of the Zr55Al10Cu30Ni5-xPdx (x=0, 1, 3, 5 at. pct) alloys upon copper-mold casting has been investigated. The structure, thermal stability and microstructure were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM), respectively. It was identified that a new bulk amorphous alloy with the larger supercooled liquid region Tx of 100 K is obtained with substituting Ni by 1 at. pct Pd. Furthermore, the origins that thermal stability and GFA change with increasing of Pd have also beer discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.:51434008,51671166,51471143)。
文摘Many amorphous alloys have been developed to date,but the low plasticity has limited their application.To achieve an amorphous alloy with high plasticity,a series of(Ti_(40)Zr_(25)Cu_(9)Ni_(8) Be_(18))_(100-x)TM_(x)(x=0,1,2,3,4 at.%,TM=Nb,Y)alloys were designed to study the influence of Nb and Y addition on the plasticity.The amorphous samples were prepared using the vacuum melting and copper mold casting process.The microstructures,glass forming ability and mechanical properties of the alloys were investigated by X-ray diffractometry(XRD),scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HRTEM),depth-sensitive nanoindentation,and uniaxial compressive test.The plasticity of different bulk amorphous alloys was investigated by measuring the plastic deformation energy(PDE)during loading.The relationship between the PDE value and plasticity in bulk amorphous alloys was explored.Results show that Nb addition decreases the PDE value and promotes the generation of multiple shear bands,which significantly increases the fracture strength and plasticity,while the addition of Y element reduces the fracture strength and plastic strain of the alloy.
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).
文摘The structures of the bulk amorphous Zr41Ti14Cu12.5Nil0.0Be22.5 alloy have been analyzed in solid, supercooled liquid and liquid with X-ray diffraction. The first coordination sphere radii and the first coordination numbers are 0.312 um, 11.2 in solid state.10.932 nm, 10.932 in supercooled liquid region and 0.305 urn, 11.296 in liquid state. The structures are the same in different states. But it shows some tendency to crystallizing that the first coordination sphere radius and the first coordination number drop in supercooled liquid region.
基金The National Natural Science Foundation of China （50471077） the Ministry of Science and Technology of China （2006CB605201, 2005DFA50860） supported this work.
文摘Designing and synthesis of cost effective bulk metallic glasses （BMGs） has been of considerable interest during the last decade so that they can be made commercially viable. Among these, Zr-based BMGs have been reported extensively due to their attractive properties, An alloy having composition Zr65Cu18Ni9A18 was designed and synthesized using 2-3 N pure materials by Cu mould casting. The alloy was characterized by X- ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDS） and high temperature differential scanning calorimetry （DSC）. Thermal parameters like supercooled liquid region △Tx, reduced glass transition temperature Trg, γ and δ parameters were evaluated. Mechanical properties like microhardness, nanohardness, elastic modulus and fracture strength were measured. The alloy showed wide supercooled liquid region of 129＋1 K with improved thermal stability. The alloy has considerable fracture strength along with fair amount of ductility.
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supported by the National Natural Science Foundation of China(Grant no.52071278/51827801)the National Key Research and Development Program of China(Grant no.2018YFA0703603)。
文摘In this study,Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloys samples with the same diameter(8 mm)were prepared by using self-designed molds(viz.refractory steel,pure graphite,and copper molds)with different cooling capacities.Moreover,by eliminating the size effect,the effect of the cooling rate on the microstructure and compression deformation behavior of Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloys was investigated.Differentiation of the cooling curves revealed that the instantaneous cooling rates of the alloy melt at the glass transition temperature(Tg)are 45,52,and 64 K·s^(-1) for refractory steel,pure graphite,and copper molds,respectively.X-ray diffraction,differential scanning calorimetry,and highresolution transmission electron microscopy analysis revealed that with the decrease in the cooling rate,trace icosahedral-like atomic clusters and nanocrystals appear in local areas of the amorphous alloy and that the amount of free volume decreases with the increase in the amount of icosahedra-like atomic clusters and nanocrystals.Compression test results revealed that the elastic strain,yield strength,and compressive strength of the amorphous alloy marginally change with the decrease in the cooling rate,while the plastic strain gradually increases.By fitting,the effective size of the vein-like pattern was linearly related to the enthalpy released during structural relaxation and plastic strain,indicating that at a low cooling rate,the trace nanocrystals in the amorphous alloy could not effectively improve its plasticity and that the amount of free volume mainly affects its plasticity.
