To clarify phase transformation evolution of Nb-doped Ni-Mn-Ga bulk alloys after aging and ball milling, the microstructure and phase transformation of the aged and ball-milled dual-phase Nb-doped Ni-Mn-Ga alloys were...To clarify phase transformation evolution of Nb-doped Ni-Mn-Ga bulk alloys after aging and ball milling, the microstructure and phase transformation of the aged and ball-milled dual-phase Nb-doped Ni-Mn-Ga alloys were investigated by SEM, EDS, XRD, DSC and susceptibility measurements. The as-cast alloys were mainly composed of the second phase with layer-shape and presented a reduced martensitic transformation with increasing the second phase content. The second phase transformed from layer-shape to dense bar-shape and the martensitic transformation was enhanced after being quenched at 1173 K. After aging at 673 and 873 K, the 3% Nb alloy with less second phase exhibited a single-step phase transformation, whereas the 6% Nb and 9% Nb alloys with more second phase exhibited a two-step martensitic transformation and Curie transition. The martensitic transformation and Curie transition of the as-milled dual-phase particles disappeared and were retrieved after annealing at 1073 K due to the recovery of high ordered structure of the matrix.展开更多
Al-xV alloys(x=2 at.%,5 at.%,10 at.%)with nanocrystalline structure and high solid solubility of V were produced in powder form by high-energy ball milling(HEBM).The alloy powders were consolidated by spark plasma sin...Al-xV alloys(x=2 at.%,5 at.%,10 at.%)with nanocrystalline structure and high solid solubility of V were produced in powder form by high-energy ball milling(HEBM).The alloy powders were consolidated by spark plasma sintering(SPS)employing a wide range of temperatures ranging from 200 to 400°C.The microstructure and solid solubility of V in Al were investigated using X-ray diffraction analysis,scanning electron microscope and transmission electron microscope.The microstructure was influenced by the SPS temperature and V content of the alloy.The alloys exhibited high solid solubility of V–six orders of magnitude higher than that in equilibrium state and grain size<50 nm at all the SPS temperatures.The formation of Al3V intermetallic was detected at 400℃.Formation of a V-lean phase and bimodal grain size was observed during SPS,which increased with the increase in SPS temperature.The hardness and elastic modulus,measured using nanoindentation,were significantly higher than commercial alloys.For example,Al-V alloy produced by SPS at 200℃ exhibited a hardness of 5.21 GPa along with elastic modulus of 96.21 GPa.The evolution of the microstructure and hardness with SPS temperatures has been discussed.展开更多
Hydrogen storage and microstructure of ball milled Mg3La alloy were investigated by X-ray diffraction and pressure-composition-isotherm measurement. The ball milled Mg3La alloy could absorb hydrogen up to 4wt.% at 300...Hydrogen storage and microstructure of ball milled Mg3La alloy were investigated by X-ray diffraction and pressure-composition-isotherm measurement. The ball milled Mg3La alloy could absorb hydrogen up to 4wt.% at 300 ℃ for the first time, along with a decomposing course. Following tests showed that the average reversible hydrogen storage capacity was 2.7wt.%. The enthalpy and entropy of dehydrogenation reaction of the decomposed ball milled Mg3La and hydrogen were calculated. XRD patterns indicated the existence of MgH2 and LaH3 in the decomposed hydride and the formation of Mg when hydrogen was desorbed. After the first hydrogenation, all the latter hydrogenation/dehydrogenation reactions could be taken place between Mg and MgH2. The ball milled Mg3La alloy exhibited better hydriding kinetics than that of the as-cast Mg3La alloy at room temperature. The kinetic curve could be well fitted by Avrami-Erofeev equation.展开更多
Bimodal-grained Ti containing coarse and fine grains was fabricated by high-energy ball milling and spark plasma sintering (SPS). The microstructure and mechanical properties of the compacts sintered by Ti powders bal...Bimodal-grained Ti containing coarse and fine grains was fabricated by high-energy ball milling and spark plasma sintering (SPS). The microstructure and mechanical properties of the compacts sintered by Ti powders ball-milled for different time were studied. Experimental results indicated that when the ball-milling time increased, the microstructure of sintered Ti was firstly changed from coarse-grained to bimodal-grained structure, subsequently transformed to a homogeneous fine-grained structure. Compared with coarse-grained Ti and fine-grained Ti, bimodal-grained Ti exhibited balanced strength and ductility. The sample sintered from Ti powders ball-milled for 10 h consisting of 65.3% (volume fraction) fine-grained region (average grain size 1 μm) and 34.7% coarse-grained region (grain size > 5 μm) exhibited a compress strength of 1028 MPa as well as a plastic strain to failure of 22%.展开更多
A new self-made additive of amidocyanogen-acetic salt was used in wet ball-grind technique (WBGT) for preparing hydrogen storage alloys, and the effect on the electrochemical performance of the alloy electrode was i...A new self-made additive of amidocyanogen-acetic salt was used in wet ball-grind technique (WBGT) for preparing hydrogen storage alloys, and the effect on the electrochemical performance of the alloy electrode was investigated in detail. It was found that the prepared electrode had perfect electrochemical performances, such as rapid activation, high capability, high-rate discharge (HRD) ability, and good stability. The first discharge capacitance at 0.2 C (throughout this study, n C rate means that the rated capacity of a hydrogen storage alloy (full capacity) is charged or discharged completely in 1/n h) reached 278 mAh·g^-1 and the discharge capacitance reached the maximum of 322 mAh·g^-1 only after two charge-discharge cycles. For the dry method, wet method, and WBGT, the high rate discharge (HRD) values (C5 c/C0.2c ratio) were approximately 0.59, 0.76, and 0.83, respectively. The stable discharge capacity at 3 C increased from 275 mAh·g^-1 (dry method)to 295 mAh·g^-1 (WBGT).展开更多
This study investigated the effects of carbon nanotube (CNT) concentration on the micro-morphologies and laser absorption proper- ties of CNT/AlSi10Mg composite powders produced by high-energy ball milling. A scanni...This study investigated the effects of carbon nanotube (CNT) concentration on the micro-morphologies and laser absorption proper- ties of CNT/AlSi10Mg composite powders produced by high-energy ball milling. A scanning electron microscope, X-ray diffractometer, laser particle size analyzer, high-temperature synchronous thermal analyzer, and UV/VIS/NIR spectrophotometer were used for the analysis of micro- graphs, phases, granulometric parameters, thermal properties, and laser absorption properties of the composite powders, respectively. The results showed that the powders gradually changed from flake- to granule-like morphology and the average particle size sharply decreased with in- creases in milling rotational speed and milling time. Moreover, a uniform dispersion of CNTs in AlSi10Mg powders was achieved only for a CNT content of 1.5wt%. Laser absorption values of the composite powders were also observed to gradually increase with the increase of CNT concentration, and different spectra displayed characteristic absorption peaks at a wavelength of approximately 826 nm.展开更多
Ti and Ag powders were mixed with different ball milling time (1, 2, 5 and 10 h) and sintered into porous Ti-3Ag alloys. The samples were treated with hydrothermal treatment, and their apatite-inducing abilities wer...Ti and Ag powders were mixed with different ball milling time (1, 2, 5 and 10 h) and sintered into porous Ti-3Ag alloys. The samples were treated with hydrothermal treatment, and their apatite-inducing abilities were further evaluated by immersion in modified simulated body fluid. The results indicate that the high surface energy brought by powder refinement leads to the decline of Ag, but promotes the oxidation of Ti during the sintering process. Meanwhile, the hydrothermal treated porous Ti-3Ag alloys prepared by the powders ball milled for 10 h possess the best apatite-inducing ability.展开更多
The effect of ball milling on the microstructural evolution was investigated during partial remelting of 6061 aluminum alloy prepared by cold-pressing of atomized alloy powders.The results indicate that the microstruc...The effect of ball milling on the microstructural evolution was investigated during partial remelting of 6061 aluminum alloy prepared by cold-pressing of atomized alloy powders.The results indicate that the microstructural evolution of 6061 aluminum alloy can be divided into three stages,the dissolution of eutectic phases and the coarsening and growth behavior of the resulting grains,structural separation and spheroidization of primary particles,and the final coarsening behavior of the particles.Compared with the alloy without ball milling,ball milling accelerates the first stage of microstructural evolution due to the energy stored in the powders,but the latter two stages are slowed down because of the formation of large-sized powders.Moreover,the finer the as-cold-pressed microstructure is,the smaller and more spherical the primary particles in the final semisolid microstructure are.Furthermore,properly elevating the heating temperature is beneficial for obtaining small and spheroidal particles.展开更多
The amorphous Mg_(0.94)La_(0.06)Ni alloy was synthesized by ball milling for different time at 400 r·min^(-1). Electrochemical performances of the alloy electrodes were investigated and the results show that the ...The amorphous Mg_(0.94)La_(0.06)Ni alloy was synthesized by ball milling for different time at 400 r·min^(-1). Electrochemical performances of the alloy electrodes were investigated and the results show that the specimens would reach their maximum electrochemical discharge capacities at the first charge/discharge cycle. The cyclic tests and X-ray diffraction (XRD) results show that discharge capacities would decrease rapidly due to the crystallization of the amorphous and the oxidization of magnesium on the particle surface during the electrochemical charge/discharge cycling. In addition, the DTA and SEM results reveal that the thermal stabilities will be improved and the size of the alloy will be decreased with the ball-milling time. The amorphous Mg_(0.96)La_(0.04)Ni alloy prepared by ball milling for 40 h at 400 r·min^(-1) shows the best electrochemical properties.展开更多
The microwave magnetic properties of the ball milled FeCo panicles were investigated as functions of ball milling time ( t ) using microwave electromagnetic parameters analysis techniques. The results show that the ...The microwave magnetic properties of the ball milled FeCo panicles were investigated as functions of ball milling time ( t ) using microwave electromagnetic parameters analysis techniques. The results show that the imaginary part of intrinsic dynamic permeability ( ui ) of the ball- milled panicles is much bigger than that of raw powders. ui strongly depends on t and exhibits several slightly damped ferromagnetic resonances. These phenomena are in qualitative agreement with the formation of the corresponding microstructure or the Aharoni ' s model of non-uniform exchange resonance modes. The present microwave permeabilhy behavior indicates that nanocrystalline materials with the same grain size may exhibit different properties that depend upon the microstructure, which provides a possibility for manufacturing high performance microwave absorber.展开更多
The influence of spark plasma sintering(SPS)temperature on microstructure,hardness and corrosion behavior of a high-energy ball milled Mg-10wt%Al alloy was investigated in this work.The holding time and sintering pres...The influence of spark plasma sintering(SPS)temperature on microstructure,hardness and corrosion behavior of a high-energy ball milled Mg-10wt%Al alloy was investigated in this work.The holding time and sintering pressure for SPS were kept constant while varying the sintering temperature from 200 to 350℃.The grain size and microstructure were studied using X-ray diffraction analysis,scanning electron microscopy,energy dispersive X-ray spectroscopy,and Archimedes'based density measurement.Corrosion behavior was investigated using potentiodynamic polarization tests.The nanocrystalline regime(grain size<100nm)was maintained even after SPS up to 350℃.The density of the alloy increased with increasing the SPS temperature.Vickers'hardness and corrosion performance improved up to 300℃ followed by a decrease after SPS at 350℃.Possible reasons for densification,strengthening,and corrosion behavior have been discussed in the light of reduced porosity and microstructural changes.展开更多
To compare the hydrogen storage performances of as-milled REMg11Ni-5MoS2(mass fraction)(RE=Y,Sm)alloys,which were catalyzed by MoS2,the corresponding alloys were prepared.The hydrogen storage performaces of these allo...To compare the hydrogen storage performances of as-milled REMg11Ni-5MoS2(mass fraction)(RE=Y,Sm)alloys,which were catalyzed by MoS2,the corresponding alloys were prepared.The hydrogen storage performaces of these alloys were measured by various methods,such as XRD,TEM,automatic Sievert apparatus,TG and DSC.The results reveal that both of the as-milled alloys exhibit a nanocrystalline and amorphous structure.The RE=Y alloy shows a larger hydrogen absorption capacity,faster hydriding rate,lower initial hydrogen desorption temperature,superior hydrogen desorption property,and lower hydrogen desorption activation energy,which is thought to be the reason of its better hydrogen storage kinetics,as compared with RE=Sm alloy.展开更多
In order to understand the fundamentals of a high energy vibrating type milling process, the energy transfer during me-chanical alloying of molybdenum disilicide is investigated based on the Magini-Iasonna energy tran...In order to understand the fundamentals of a high energy vibrating type milling process, the energy transfer during me-chanical alloying of molybdenum disilicide is investigated based on the Magini-Iasonna energy transfer method, amended by Murty. The efficiency factor and total energy of milling are calculated. MoSi2 synthesized by a mechanically induced self-propagating reaction has also been studied according to different milling parameters, such as the number of balls and the ball to powder weight ratio. The results indicate that the efficiency factor is between 1.944 and 8.507 J/(g·s). A total milling energy of about 19.38–26.47 kJ/g is found to be necessary for the mechanically induced self-propagating reaction of a Mo:2Si powder mixture. The efficiency of milling energy transfer is about 3.3%–4.5%. The experiment and modeling show that the optimum condition for mechanical alloy-ing is a half full vial of balls.展开更多
A new model of multirange fractals is proposed to explain the experimental results observed on the fractal dimensions of the fractured surfaces in materials. A new explanation to the Williford's multifractal curve...A new model of multirange fractals is proposed to explain the experimental results observed on the fractal dimensions of the fractured surfaces in materials. A new explanation to the Williford's multifractal curve on the relationship of fractal dimension with fracture properties in materials has been given. It shows the importance of fractorizing out the effect of fractal structure from other physical causes and separating the appropriate range of scale from multirange fractals. Mechanical alloying process under ball milling as a non-equilibrium dynamical system has been also analyzed.展开更多
The nanostractures of the ball milled FeCo particles were characterized as functions of the ball milling time ( t ) using quantitative X- ray diffraction ( XRD ), high resolution transmission electron microscopy ...The nanostractures of the ball milled FeCo particles were characterized as functions of the ball milling time ( t ) using quantitative X- ray diffraction ( XRD ), high resolution transmission electron microscopy (HRTEM) analysis techniques. The results show that the nanocrystalliue bcc FeCo particles are available using carbonyl iron and cobalt powders as the start materials during the high-energy ball milling. At the early stage of ball milling, Co powders are easily mashed into nanocrystalllites, by which the surface of the larger Fe particles of about 80- 150 nm is coated. With t increasing, the refinement of grain size and the incorporation of defects including dislocations, disclinations and grain boundaries happen, and then FeCo alloy with a certain layered structure is formed, finally the layered stractare disappears with the formation of isotropic grains having a steadystate grain size in the nanometer regime after a certain period of t.展开更多
Amorphous Ni-Pd-Si ribbons were partially crystallized by relaxation treatment then secondary amorphous Ni-Pd-Si alloy powder prepared by mechanical milling. The surface states of amorphous and crystalline Ni-Pd-Si po...Amorphous Ni-Pd-Si ribbons were partially crystallized by relaxation treatment then secondary amorphous Ni-Pd-Si alloy powder prepared by mechanical milling. The surface states of amorphous and crystalline Ni-Pd-Si powders were studied by XRD, TEM, AES and ESCA spectra. The catalytic activities of amorphous and crystalline powders in hydrogenation of styrene was measured.The result shows that the catalytic activity of amorphous Ni-Pd-Si powder was higher than that of crystalline one by 6 times in hydrogenation of styrene.展开更多
A TiAl alloy was fabricated by high-energy ball milling and subsequent reactive sintering from the mixed powders of Ti and Al. High-energy ball milling produced a kind of particular composite powders with an extremely...A TiAl alloy was fabricated by high-energy ball milling and subsequent reactive sintering from the mixed powders of Ti and Al. High-energy ball milling produced a kind of particular composite powders with an extremely fine altemative Ti and Al lamella structure. The composite powders not only possessed good consolidation and densification characteristics, but also resulted in the augment of nucleation rate of α and γ titanium aluminides during solid-phase reactive sintering After a series of processing, pressing, degassing, extrusion, and sintering, the resultant TiAl alloy presented high relative density and refined grain sizes of (α2 + γ) lamella and γ phases. The compressive yield strength of the sintered TiAl reached 600 MPa at 800℃.展开更多
The melt spinning(MS) and ball milling(BM) technologies are thought to be efficient to prepare nanostructured Mg and Mg-based alloys for improving their hydrogen storage performances. In this paper, two technologi...The melt spinning(MS) and ball milling(BM) technologies are thought to be efficient to prepare nanostructured Mg and Mg-based alloys for improving their hydrogen storage performances. In this paper, two technologies, viz. melt spinning and ball milling, were employed to fabricate the SmMg_(11)Ni alloy. The structure and hydrogen storage performance of these two kinds of alloys were researched in detail. The results reveal that the as-spun and milled alloys both contain nanocrystalline and amorphous structures. By means of the measurement of PCT curves, the thermodynamic parameters of the alloys prepared by MS and BM are ΔN_(Ms)(des) = 82.51 kJ/mol and ΔH_(BM)(des) = 81.68 kJ/mol, respectively, viz.ΔH_(MS)(des) 〉 ΔH_(BM)(des). The as-milled alloy shows a larger hydrogen absorption capacity as compared with the as-spun one. The as-milled alloy exhibits lower onset hydrogen desorption temperature than the as-spun one. As to the as-milled and spun alloys, the onset hydrogen desorption temperatures are557.6 and 565.3 K, respectively. Additionally, the as-milled alloy shows a superior hydrogen desorption property than the as-spun one. On the basis of time that required by desorbing hydrogen of 3 wt% H_2, the as-milled alloy needs 1488.574,390 and 192 s corresponding to hydrogen desorption temperatures 593,613,633 and 653 K, while the as-spun alloy needs 3600,1020,778 and 306 s corresponding to the same temperatures. The dehydrogenation activation energies of the as-milled and spun alloys are 100.31 and105.56 kJ/mol, respectively, the difference of which is responsible for the much faster dehydriding rate of the as-milled alloy.展开更多
Mechanically activated disproportionation of Nd 12 Fe 82 B 6 alloy by ball milling in hydrogen atmosphere was experimentally investigated. The aspects of thermodynamics and kinetics for the mechanically activated disp...Mechanically activated disproportionation of Nd 12 Fe 82 B 6 alloy by ball milling in hydrogen atmosphere was experimentally investigated. The aspects of thermodynamics and kinetics for the mechanically activated disproportionation of the NdFeB alloy were discussed. Both the evolution of the disproportionation reaction and the corresponding microstructure change of the alloy during milling were characterized by X ray diffraction (XRD) analysis. The results show that the matrix phase Nd 2Fe 14 B of the as cast Nd 12 Fe 82 B 6 alloy can be disproportionated into a mixture of Nd hydride (H 5Nd 2), FeB/Fe 2B, and α Fe, by ball milling under hydrogen pressure of 0.2 MPa. The as disproportionated phases are of the size about 20 nm, suggesting that ball milling in hydrogen is an effective route for low temperature disproportionation processing of the NdFeB alloy to ensure a full nano structured as disproportionated microstructure. This is the basis for synthesizing Nd 2Fe 14 B/ α Fe nano composites with magnetic exchange coupling effect by subsequent desorption recombination processing.展开更多
The effect of post annealing on the phase transformation of Ni52Mn24Ga24 ferromagnetic shape memory alloy particles prepared by ball milling was studied. Ni52Mn24Ga24 alloy particles at micron scale were prepared succ...The effect of post annealing on the phase transformation of Ni52Mn24Ga24 ferromagnetic shape memory alloy particles prepared by ball milling was studied. Ni52Mn24Ga24 alloy particles at micron scale were prepared successfully by ball milling the crushed bulk alloy. SEM observation reveals that the shape of the as-milled particle is regular polygon and a lot of cracks can be seen at the surface of the particles. For as-milled particles,the widening of characteristic peak can be found in the XRD pattern,and no transformation characterization can be detected by DSC. Post annealing at the elevated temperature will recover the transformation behavior of milled particles to the same level as that of bulk sample. It is shown that with increasing annealing temperature above 400 ℃,Ms decreases and As increases,while the magnetic transition temperature keeps constant. XRD results indicate that the change of grain size of the particles results in such an effect of post annealing.展开更多
基金Project(51201044) supported by the National Natural Science Foundation of ChinaProject(HEUCFG201836) supported by the Fundamental Research Funds for the Central Universities,China+1 种基金Project(LBH-Q16046) supported by the Postdoctoral Scientific Research Developmental Fund of Heilongjiang Province,ChinaProject supported by the Key Laboratory of Superlight Materials&Surface Technology(Harbin Engineering University),Ministry of Education,China
文摘To clarify phase transformation evolution of Nb-doped Ni-Mn-Ga bulk alloys after aging and ball milling, the microstructure and phase transformation of the aged and ball-milled dual-phase Nb-doped Ni-Mn-Ga alloys were investigated by SEM, EDS, XRD, DSC and susceptibility measurements. The as-cast alloys were mainly composed of the second phase with layer-shape and presented a reduced martensitic transformation with increasing the second phase content. The second phase transformed from layer-shape to dense bar-shape and the martensitic transformation was enhanced after being quenched at 1173 K. After aging at 673 and 873 K, the 3% Nb alloy with less second phase exhibited a single-step phase transformation, whereas the 6% Nb and 9% Nb alloys with more second phase exhibited a two-step martensitic transformation and Curie transition. The martensitic transformation and Curie transition of the as-milled dual-phase particles disappeared and were retrieved after annealing at 1073 K due to the recovery of high ordered structure of the matrix.
基金the financial support received from the National Science Foundation(Nos.NSF-CMMI 1760204 and 2131440)under the direction of Dr.Alexis Lewissupported by the State of North Carolina and the National Science Foundation(No.ECCS-1542015)support from the National Science Foundation(DMR1726294)。
文摘Al-xV alloys(x=2 at.%,5 at.%,10 at.%)with nanocrystalline structure and high solid solubility of V were produced in powder form by high-energy ball milling(HEBM).The alloy powders were consolidated by spark plasma sintering(SPS)employing a wide range of temperatures ranging from 200 to 400°C.The microstructure and solid solubility of V in Al were investigated using X-ray diffraction analysis,scanning electron microscope and transmission electron microscope.The microstructure was influenced by the SPS temperature and V content of the alloy.The alloys exhibited high solid solubility of V–six orders of magnitude higher than that in equilibrium state and grain size<50 nm at all the SPS temperatures.The formation of Al3V intermetallic was detected at 400℃.Formation of a V-lean phase and bimodal grain size was observed during SPS,which increased with the increase in SPS temperature.The hardness and elastic modulus,measured using nanoindentation,were significantly higher than commercial alloys.For example,Al-V alloy produced by SPS at 200℃ exhibited a hardness of 5.21 GPa along with elastic modulus of 96.21 GPa.The evolution of the microstructure and hardness with SPS temperatures has been discussed.
基金Hi-Tech Research and Development Program of China (863 Program) (2006AA05Z133, 2007AA05Z110)NCETU-2006 and NSFC (50771045, 50631020)
文摘Hydrogen storage and microstructure of ball milled Mg3La alloy were investigated by X-ray diffraction and pressure-composition-isotherm measurement. The ball milled Mg3La alloy could absorb hydrogen up to 4wt.% at 300 ℃ for the first time, along with a decomposing course. Following tests showed that the average reversible hydrogen storage capacity was 2.7wt.%. The enthalpy and entropy of dehydrogenation reaction of the decomposed ball milled Mg3La and hydrogen were calculated. XRD patterns indicated the existence of MgH2 and LaH3 in the decomposed hydride and the formation of Mg when hydrogen was desorbed. After the first hydrogenation, all the latter hydrogenation/dehydrogenation reactions could be taken place between Mg and MgH2. The ball milled Mg3La alloy exhibited better hydriding kinetics than that of the as-cast Mg3La alloy at room temperature. The kinetic curve could be well fitted by Avrami-Erofeev equation.
基金Project(51104066)supported by the National Natural Science Foundation of ChinaProjects(2015A010105011,2015A020214008)supported by Science and Technology Program of Guangdong Province,ChinaProject(201505040925029)supported by Science and Technology Research Program of Guangzhou,China
文摘Bimodal-grained Ti containing coarse and fine grains was fabricated by high-energy ball milling and spark plasma sintering (SPS). The microstructure and mechanical properties of the compacts sintered by Ti powders ball-milled for different time were studied. Experimental results indicated that when the ball-milling time increased, the microstructure of sintered Ti was firstly changed from coarse-grained to bimodal-grained structure, subsequently transformed to a homogeneous fine-grained structure. Compared with coarse-grained Ti and fine-grained Ti, bimodal-grained Ti exhibited balanced strength and ductility. The sample sintered from Ti powders ball-milled for 10 h consisting of 65.3% (volume fraction) fine-grained region (average grain size 1 μm) and 34.7% coarse-grained region (grain size > 5 μm) exhibited a compress strength of 1028 MPa as well as a plastic strain to failure of 22%.
文摘A new self-made additive of amidocyanogen-acetic salt was used in wet ball-grind technique (WBGT) for preparing hydrogen storage alloys, and the effect on the electrochemical performance of the alloy electrode was investigated in detail. It was found that the prepared electrode had perfect electrochemical performances, such as rapid activation, high capability, high-rate discharge (HRD) ability, and good stability. The first discharge capacitance at 0.2 C (throughout this study, n C rate means that the rated capacity of a hydrogen storage alloy (full capacity) is charged or discharged completely in 1/n h) reached 278 mAh·g^-1 and the discharge capacitance reached the maximum of 322 mAh·g^-1 only after two charge-discharge cycles. For the dry method, wet method, and WBGT, the high rate discharge (HRD) values (C5 c/C0.2c ratio) were approximately 0.59, 0.76, and 0.83, respectively. The stable discharge capacity at 3 C increased from 275 mAh·g^-1 (dry method)to 295 mAh·g^-1 (WBGT).
基金financially supported by the National Natural Science Foundation of China (No. 51405467)the Research Fund for Scientific and Technological Projects of Chongqing (Nos. 2012ggB 40003 and cstc2013yykfC 00006)
文摘This study investigated the effects of carbon nanotube (CNT) concentration on the micro-morphologies and laser absorption proper- ties of CNT/AlSi10Mg composite powders produced by high-energy ball milling. A scanning electron microscope, X-ray diffractometer, laser particle size analyzer, high-temperature synchronous thermal analyzer, and UV/VIS/NIR spectrophotometer were used for the analysis of micro- graphs, phases, granulometric parameters, thermal properties, and laser absorption properties of the composite powders, respectively. The results showed that the powders gradually changed from flake- to granule-like morphology and the average particle size sharply decreased with in- creases in milling rotational speed and milling time. Moreover, a uniform dispersion of CNTs in AlSi10Mg powders was achieved only for a CNT content of 1.5wt%. Laser absorption values of the composite powders were also observed to gradually increase with the increase of CNT concentration, and different spectra displayed characteristic absorption peaks at a wavelength of approximately 826 nm.
基金Projects(2012CB619102,2012CB619100)supported by the National Basic Research Program of ChinaProjects(2011AA030101,2011AA030103)supported by the High-tech Research and Development Program of China+1 种基金Projects(HEUCFZ1017,HEUCFR1020)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(ZD201012)supported by the Natural Science Foundation of Heilongjiang Province,China
文摘Ti and Ag powders were mixed with different ball milling time (1, 2, 5 and 10 h) and sintered into porous Ti-3Ag alloys. The samples were treated with hydrothermal treatment, and their apatite-inducing abilities were further evaluated by immersion in modified simulated body fluid. The results indicate that the high surface energy brought by powder refinement leads to the decline of Ag, but promotes the oxidation of Ti during the sintering process. Meanwhile, the hydrothermal treated porous Ti-3Ag alloys prepared by the powders ball milled for 10 h possess the best apatite-inducing ability.
基金Project(G2010CB635106)supported by the National Basic Research Program of ChinaProject(NCET-10-0023)supported by the Program for New Century Excellent Talents in University of China+1 种基金Project supported by the Program for Hongliu Outstanding Talents of Lanzhou University of Technology,ChinaProject(2014-07)supported by the Basic Scientific Research Expenses of Gansu University,China
文摘The effect of ball milling on the microstructural evolution was investigated during partial remelting of 6061 aluminum alloy prepared by cold-pressing of atomized alloy powders.The results indicate that the microstructural evolution of 6061 aluminum alloy can be divided into three stages,the dissolution of eutectic phases and the coarsening and growth behavior of the resulting grains,structural separation and spheroidization of primary particles,and the final coarsening behavior of the particles.Compared with the alloy without ball milling,ball milling accelerates the first stage of microstructural evolution due to the energy stored in the powders,but the latter two stages are slowed down because of the formation of large-sized powders.Moreover,the finer the as-cold-pressed microstructure is,the smaller and more spherical the primary particles in the final semisolid microstructure are.Furthermore,properly elevating the heating temperature is beneficial for obtaining small and spheroidal particles.
文摘The amorphous Mg_(0.94)La_(0.06)Ni alloy was synthesized by ball milling for different time at 400 r·min^(-1). Electrochemical performances of the alloy electrodes were investigated and the results show that the specimens would reach their maximum electrochemical discharge capacities at the first charge/discharge cycle. The cyclic tests and X-ray diffraction (XRD) results show that discharge capacities would decrease rapidly due to the crystallization of the amorphous and the oxidization of magnesium on the particle surface during the electrochemical charge/discharge cycling. In addition, the DTA and SEM results reveal that the thermal stabilities will be improved and the size of the alloy will be decreased with the ball-milling time. The amorphous Mg_(0.96)La_(0.04)Ni alloy prepared by ball milling for 40 h at 400 r·min^(-1) shows the best electrochemical properties.
基金Funded by the 863 High Technology Research Project ( No.2001AA339020 and 2002AA305302) fromthe Ministry of Scienceand Technology of China , and the Excellent Young Teachers Pro-gramof MOE(2002[350]) ,China
文摘The microwave magnetic properties of the ball milled FeCo panicles were investigated as functions of ball milling time ( t ) using microwave electromagnetic parameters analysis techniques. The results show that the imaginary part of intrinsic dynamic permeability ( ui ) of the ball- milled panicles is much bigger than that of raw powders. ui strongly depends on t and exhibits several slightly damped ferromagnetic resonances. These phenomena are in qualitative agreement with the formation of the corresponding microstructure or the Aharoni ' s model of non-uniform exchange resonance modes. The present microwave permeabilhy behavior indicates that nanocrystalline materials with the same grain size may exhibit different properties that depend upon the microstructure, which provides a possibility for manufacturing high performance microwave absorber.
基金RKG acknowledges the financial support from the National Science Foundation(NSF-CMMI 1846887)under the direction of Dr.Alexis Lewis.
文摘The influence of spark plasma sintering(SPS)temperature on microstructure,hardness and corrosion behavior of a high-energy ball milled Mg-10wt%Al alloy was investigated in this work.The holding time and sintering pressure for SPS were kept constant while varying the sintering temperature from 200 to 350℃.The grain size and microstructure were studied using X-ray diffraction analysis,scanning electron microscopy,energy dispersive X-ray spectroscopy,and Archimedes'based density measurement.Corrosion behavior was investigated using potentiodynamic polarization tests.The nanocrystalline regime(grain size<100nm)was maintained even after SPS up to 350℃.The density of the alloy increased with increasing the SPS temperature.Vickers'hardness and corrosion performance improved up to 300℃ followed by a decrease after SPS at 350℃.Possible reasons for densification,strengthening,and corrosion behavior have been discussed in the light of reduced porosity and microstructural changes.
基金Projects(51761032,51471054,51871125)supported by the National Natural Science Foundation of China
文摘To compare the hydrogen storage performances of as-milled REMg11Ni-5MoS2(mass fraction)(RE=Y,Sm)alloys,which were catalyzed by MoS2,the corresponding alloys were prepared.The hydrogen storage performaces of these alloys were measured by various methods,such as XRD,TEM,automatic Sievert apparatus,TG and DSC.The results reveal that both of the as-milled alloys exhibit a nanocrystalline and amorphous structure.The RE=Y alloy shows a larger hydrogen absorption capacity,faster hydriding rate,lower initial hydrogen desorption temperature,superior hydrogen desorption property,and lower hydrogen desorption activation energy,which is thought to be the reason of its better hydrogen storage kinetics,as compared with RE=Sm alloy.
基金Project 20070290523 supported by the Doctoral Fund of Ministry of Education of China
文摘In order to understand the fundamentals of a high energy vibrating type milling process, the energy transfer during me-chanical alloying of molybdenum disilicide is investigated based on the Magini-Iasonna energy transfer method, amended by Murty. The efficiency factor and total energy of milling are calculated. MoSi2 synthesized by a mechanically induced self-propagating reaction has also been studied according to different milling parameters, such as the number of balls and the ball to powder weight ratio. The results indicate that the efficiency factor is between 1.944 and 8.507 J/(g·s). A total milling energy of about 19.38–26.47 kJ/g is found to be necessary for the mechanically induced self-propagating reaction of a Mo:2Si powder mixture. The efficiency of milling energy transfer is about 3.3%–4.5%. The experiment and modeling show that the optimum condition for mechanical alloy-ing is a half full vial of balls.
文摘A new model of multirange fractals is proposed to explain the experimental results observed on the fractal dimensions of the fractured surfaces in materials. A new explanation to the Williford's multifractal curve on the relationship of fractal dimension with fracture properties in materials has been given. It shows the importance of fractorizing out the effect of fractal structure from other physical causes and separating the appropriate range of scale from multirange fractals. Mechanical alloying process under ball milling as a non-equilibrium dynamical system has been also analyzed.
基金Funded by the 863 High Technology Research Project ( No.2001AA339020 and 2002AA305302) fromthe Ministry of Scienceand Technology of China ,and bythe Excellent Young Teachers Pro-gramof MOE(2002[350])
文摘The nanostractures of the ball milled FeCo particles were characterized as functions of the ball milling time ( t ) using quantitative X- ray diffraction ( XRD ), high resolution transmission electron microscopy (HRTEM) analysis techniques. The results show that the nanocrystalliue bcc FeCo particles are available using carbonyl iron and cobalt powders as the start materials during the high-energy ball milling. At the early stage of ball milling, Co powders are easily mashed into nanocrystalllites, by which the surface of the larger Fe particles of about 80- 150 nm is coated. With t increasing, the refinement of grain size and the incorporation of defects including dislocations, disclinations and grain boundaries happen, and then FeCo alloy with a certain layered structure is formed, finally the layered stractare disappears with the formation of isotropic grains having a steadystate grain size in the nanometer regime after a certain period of t.
文摘Amorphous Ni-Pd-Si ribbons were partially crystallized by relaxation treatment then secondary amorphous Ni-Pd-Si alloy powder prepared by mechanical milling. The surface states of amorphous and crystalline Ni-Pd-Si powders were studied by XRD, TEM, AES and ESCA spectra. The catalytic activities of amorphous and crystalline powders in hydrogenation of styrene was measured.The result shows that the catalytic activity of amorphous Ni-Pd-Si powder was higher than that of crystalline one by 6 times in hydrogenation of styrene.
基金This project was financially supported by the National Natural Science Foundation of China (No. 59875015)the Natural Science Foundation of South China University of Technology (No. E5305293).
文摘A TiAl alloy was fabricated by high-energy ball milling and subsequent reactive sintering from the mixed powders of Ti and Al. High-energy ball milling produced a kind of particular composite powders with an extremely fine altemative Ti and Al lamella structure. The composite powders not only possessed good consolidation and densification characteristics, but also resulted in the augment of nucleation rate of α and γ titanium aluminides during solid-phase reactive sintering After a series of processing, pressing, degassing, extrusion, and sintering, the resultant TiAl alloy presented high relative density and refined grain sizes of (α2 + γ) lamella and γ phases. The compressive yield strength of the sintered TiAl reached 600 MPa at 800℃.
基金Project supported by the National Natural Science Foundations of China(51761032,51371094 and 51471054)Natural Science Foundation of Inner Mongolia,China(2015MS0558)
文摘The melt spinning(MS) and ball milling(BM) technologies are thought to be efficient to prepare nanostructured Mg and Mg-based alloys for improving their hydrogen storage performances. In this paper, two technologies, viz. melt spinning and ball milling, were employed to fabricate the SmMg_(11)Ni alloy. The structure and hydrogen storage performance of these two kinds of alloys were researched in detail. The results reveal that the as-spun and milled alloys both contain nanocrystalline and amorphous structures. By means of the measurement of PCT curves, the thermodynamic parameters of the alloys prepared by MS and BM are ΔN_(Ms)(des) = 82.51 kJ/mol and ΔH_(BM)(des) = 81.68 kJ/mol, respectively, viz.ΔH_(MS)(des) 〉 ΔH_(BM)(des). The as-milled alloy shows a larger hydrogen absorption capacity as compared with the as-spun one. The as-milled alloy exhibits lower onset hydrogen desorption temperature than the as-spun one. As to the as-milled and spun alloys, the onset hydrogen desorption temperatures are557.6 and 565.3 K, respectively. Additionally, the as-milled alloy shows a superior hydrogen desorption property than the as-spun one. On the basis of time that required by desorbing hydrogen of 3 wt% H_2, the as-milled alloy needs 1488.574,390 and 192 s corresponding to hydrogen desorption temperatures 593,613,633 and 653 K, while the as-spun alloy needs 3600,1020,778 and 306 s corresponding to the same temperatures. The dehydrogenation activation energies of the as-milled and spun alloys are 100.31 and105.56 kJ/mol, respectively, the difference of which is responsible for the much faster dehydriding rate of the as-milled alloy.
文摘Mechanically activated disproportionation of Nd 12 Fe 82 B 6 alloy by ball milling in hydrogen atmosphere was experimentally investigated. The aspects of thermodynamics and kinetics for the mechanically activated disproportionation of the NdFeB alloy were discussed. Both the evolution of the disproportionation reaction and the corresponding microstructure change of the alloy during milling were characterized by X ray diffraction (XRD) analysis. The results show that the matrix phase Nd 2Fe 14 B of the as cast Nd 12 Fe 82 B 6 alloy can be disproportionated into a mixture of Nd hydride (H 5Nd 2), FeB/Fe 2B, and α Fe, by ball milling under hydrogen pressure of 0.2 MPa. The as disproportionated phases are of the size about 20 nm, suggesting that ball milling in hydrogen is an effective route for low temperature disproportionation processing of the NdFeB alloy to ensure a full nano structured as disproportionated microstructure. This is the basis for synthesizing Nd 2Fe 14 B/ α Fe nano composites with magnetic exchange coupling effect by subsequent desorption recombination processing.
文摘The effect of post annealing on the phase transformation of Ni52Mn24Ga24 ferromagnetic shape memory alloy particles prepared by ball milling was studied. Ni52Mn24Ga24 alloy particles at micron scale were prepared successfully by ball milling the crushed bulk alloy. SEM observation reveals that the shape of the as-milled particle is regular polygon and a lot of cracks can be seen at the surface of the particles. For as-milled particles,the widening of characteristic peak can be found in the XRD pattern,and no transformation characterization can be detected by DSC. Post annealing at the elevated temperature will recover the transformation behavior of milled particles to the same level as that of bulk sample. It is shown that with increasing annealing temperature above 400 ℃,Ms decreases and As increases,while the magnetic transition temperature keeps constant. XRD results indicate that the change of grain size of the particles results in such an effect of post annealing.