共查询到20条相似文献,搜索用时 15 毫秒
1.
M.H. Enayati F. Karimzadeh S.Z. Anvari 《Journal of Materials Processing Technology》2008,200(1-3):312-315
The nanocrystalline NiAl intermetallic compound was synthesized by mechanical alloying of the elemental powders. The structural changes of powder particles during mechanical alloying were studied by X-ray diffractometery, scanning electron microscopy and microhardness measurements. The mechanical alloying resulted in the gradual formation of nanocrystalline NiAl with a grain size of 20 nm. It was found that NiAl phase develops by continuous diffusive reaction at Ni/Al layers interfaces. The NiAl compound exhibited high microhardness value of about 1035 Hv. 相似文献
2.
N. Al-Aqeeli G. Mendoza-Suarez A. Labrie R.A.L. Drew 《Journal of Alloys and Compounds》2005,400(1-2):96-99
Al–Mg and Al–Mg–Zr alloys were processed by mechanical alloying. The phase constitution of the powders was strongly dependent on the composition of the starting mixture. In as-milled powders, an Al(Mg) solid solution was formed with up to 40 at% Al, which after annealing transformed to the equilibrium β-Al3Mg2 phase. For high Mg concentrations (60–90 at%) the dominant phase was γ-Al12Mg17 in accordance with the equilibrium phase diagram. The addition of Zr led to the appearance of Zr–Al intermetallics causing Mg to precipitate out of the Al(Mg) solution. The effect of zirconium was also to refine the structure and to retard grain growth. 相似文献
3.
The nanocrystalline (Fe,Ti)3Al intermetallic compound was synthesized by mechanical alloying (MA) of elemental powder with composition Fe50Al25Ti25. The structural changes of powder particles during mechanical alloying were studied by X-ray diffractometry and microhardness measurements. Morphology and cross-sectional microstructure of powder particles were characterized by scanning electron microscopy. It was found that a Fe/Al/Ti layered structure was formed at the early stages of milling followed by the formation of Fe(Ti,Al) solid solution. This structure transformed to (Fe,Ti)3Al intermetallic compound at longer milling times. Upon heat treatment of (Fe,Ti)3Al phase the degree of DO3 ordering was increased. The (Fe,Ti)3Al compound exhibited high microhardness value of about 1050 Hv. 相似文献
4.
In this paper, the amorphization process in mechanical alloyed Ni---Al---Se powders has been investigated by X-ray diffraction. The influence of Se on the amorphization of Ni---Al alloys, and the influence of milling time on the powder structure, microcrystallites size and phases lattice distortion are presented. Also, the Fe and Cr content from the milling medium, after 400 h, was determined. 相似文献
5.
A new approach for deposition of in situ nanocrystalline Fe–Si alloy coating on mild steel substrate by mechanical milling has been proposed. The thickness of nanocrystalline coating was a function of milling time and speed. Milling speed of 200 rpm was the optimum condition for development of uniform, hard, adherent and dense 200–300 μm thick nanocrystalline coating. A possible mechanism, consisting of three steps like repeated impact, cold welding and delamination, has been proposed for the formation of coating. These coatings have resulted in the increase of the hardness to almost double the value before coating. 相似文献
6.
The preparation of bulk nanophase materials from nanocrystalline powders has been carried out by the application of sintering at high pressure. Fe–50 at.%Al system has been prepared by mechanical alloying for different milling periods from 1 to 50 h, using vials and balls of stainless steel and a ball-to-powder weight ratio (BPR) of 8:1 in a SPEX 8000 mill. Sintering of the 5 and 50 h milled powders was performed under high uniaxial pressure at 700 °C. The characterization of powders from each interval of milling was performed by X-ray diffraction, Mössbauer spectroscopy, scanning and transmission electron microscopy. After 5 h of milling formation of a nanocrystalline α-Fe(Al) solid solution that remains stable up to 50 h occurs. The grain size decreases to 7 nm after 50 h of milling. The sintering of the milled powders resulted in a nanophase-ordered FeAl alloys with a grain size of 16 nm. Grain growth during sintering was very small due to the effect of the high pressure applied. 相似文献
7.
In this paper we present the results of our efforts to synthesize the nanocrystalline MgB2 superconducting compound from elemental Mg and B powders by combination of controlled mechanical pre-alloying in a magneto-mill Uni-Ball-Mill 5 under shearing mode followed by electrical discharge (ED) assisted mechanical alloying (MA). There is no conclusive evidence of MgB2 formation in the Mg-2B mixture using crystalline boron after controlled mechanical alloying (CMA) under protective argon or helium atmosphere as well as subsequent ED assisted alloying. There seems to be some XRD evidence of the strongest (1 0 1) MgB2 peak presence in the Mg-2B mixture processed using both crystalline and amorphous boron after CMA under hydrogen as well as subsequent ED assisted alloying but this evidence is rather ambiguous. We postulate here that it is highly likely that a certain critical Mg nanograin size must be achieved before a successful reaction to form nanocrystalline MgB2 is going to be completed. Following recent report by Gümbel et al. [Appl. Phys. Lett. 80 (2002) 2725] this critical value can be roughly estimated at 15 nm or less. Calculations of the Mg nanograin size in the present work show that only three Mg-2B powders ball milled under hydrogen meet this critical nanograin size criterion for the Mg phase. However, a massive formation of the β-MgH2 hydride in these powders consumes the available Mg in the reaction with hydrogen which may leave inadequate concentration of Mg to form MgB2 even though the nanograin size of Mg is sufficiently refined, say below 15 nm. 相似文献
8.
Shuguang Cai Xianfeng Ma Huaguo Tang Wei Zhao Junmin Yan Bo Zhao Zhuhui Qiao 《Journal of Alloys and Compounds》2007,430(1-2):77-80
Single phase WXAl50Mo50−X (X = 40, 30, 20 and 10) powders have been synthesized directly by mechanical alloying (MA). The structural evolutions during MA and subsequent as-milled powders by annealing at 1400 °C have been analyzed using X-ray diffraction (XRD). Different from the Mo50Al50 alloy, W40Al50Mo10 and W30Al50Mo20 alloys were stable at 1400 °C under vacuum. The results of high-pressure sintering indicated that the microhardnesses of two compositions, namely W40Al50Mo10 and W30Al50Mo20 alloys have higher values compared with W50Al50 alloy. 相似文献
9.
MgCNi3, an intermetallic compound with superconductivity, was synthesized from the Mg (or Mg2Ni), Ni and graphite powders by mechanical alloying (MA). It is shown that the preliminary condition for the formation of MgCNi3 is that Mg2Ni must form in advance of MgCNi3 in the MA process or be the starting component. 相似文献
10.
Phase formation during high energy ball milling of a ternary elemental powder mixture with a composition of Al–27.4at%Fe–28.7at%C and during low temperature heat treatment of the milled powder was studied. It was found that an amorphous phase formed during prolonged milling. During heating the shorter time milled powder, Al and Fe reacted first, forming the AlFe phase and then at a higher temperature, AlFe reacts with Fe and C, forming the AlFe3C0.5 phase. During heating the longer time milled powder which contains a substantial amount of amorphous phase, the amorphous phase partially crystallizes first, forming the AlFe and AlFe3C0.5 phases, and then AlFe reacts with the remaining amorphous phase, forming the AlFe3C0.5 phase. Overall, mechanical alloying of Al, Fe and C elemental phases enables formation of an amorphous phase, while low temperature heat treatment of mechanically milled powder facilitates formation of AlFe and AlFe3C0.5 phases. 相似文献
11.
Amir Hossein Taghvaei Mihai StoicaGavin Vaughan Mohammad GhaffariSaeed Maleksaeedi Kamal Janghorban 《Journal of Alloys and Compounds》2012,512(1):85-93
In this work, microstructural evolution and amorphous phase formation in Co40Fe22Ta8B30 alloy produced by mechanical alloying (MA) of the elemental powder mixture under argon gas atmosphere was investigated. Milling time had a profound effect on the phase transformation, microstructure, morphological evolution and thermal behavior of the powders. These effects were studied by the X-ray powder diffraction (XRD) in reflection mode using Cu Kα and in transmission configuration using synchrotron radiation, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The results showed that at the early stage of the milling, microstructure consisted of nanocrystalline bcc-(Fe, Co) phases and unreacted tantalum.Further milling, produced an amorphous phase, which became a dominant phase with a fraction of 96 wt% after 200 h milling. The DSC profile of 200 h milled powders demonstrated a huge and broad exothermic hump due to the structural relaxation, followed by a single exothermic peak, indicating the crystallization of the amorphous phase. Further XRD studies in transmission mode by synchrotron radiation revealed that the crystalline products were (Co, Fe)20.82Ta2.18B6, (Co, Fe)21 Ta2 B6, and (Co, Fe)3B2. The amorphization mechanisms were discussed in terms of severe grain refinement, atomic size effect, the concept of local topological instability and the heat of mixing of the reactants. 相似文献
12.
The microstructural evolution of nanocrystalline Cu-10%Nb(mass fraction) alloy during mechanical alloying (MA) was investigated by using X-ray diffraction, optical microscopy(OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation. Upon milling of Cu-Nb powders with coarse grains, the grain size is found to decrease gradually with lengthening milling time, and reach the minimum value (about 9 nm) after 100 h milling. The microstrain and the microhardness of the powders increase during the grain refinement. And Cu lattice parameter increases steadily over 100 h milling. The mechanisms of solid solution extension during milling were discussed. The results show that up to 10%Nb can be brought into solid solution by MA. The extension of solid solution is found to relate closely with the formation of nanocrystalline. 相似文献
13.
《Intermetallics》2015
In the present investigation, we have studied the phase transformation of the CuAl2 intermetallic alloy with tetragonal structure by high-energy ball-milling. The structural changes with milling time were followed by X-ray diffraction, differential scanning calorimetry and electron microscopy. It is found that CuAl2-phase transforms to body centered cubic structure after a long periods of high-energy ball-milling time. According to SEM results, the milling powders change their mechanical behavior from brittle to ductile during the phase transformation. Rietveld analysis showed that around 29% of unit cells in the metastable cubic structure are occupied by Cu suggesting Al segregation in the material and explaining the change in the mechanical behavior of the alloy. 相似文献
14.
In this study, nanocrystalline NiAl intermetallic compound was obtained by mechanical alloying and PAS (plasma activated sintering
method). Nanocrystalline NiAl powder was fabricated after 30 hr of milling with 2 wt.% stearic acid added as a PCA (process
control agent) to the Ni-50at%Al composition. The grain size of the nanocrystalline NiAl powder was about 10 nm. Nanocrystalline
NiAl powder was consolidated at 1000°C, 1100°C, 1200°C and 1300°C for 2 min with 30 MPa compressive force. The surface morphology
of the NiAl consolidated at 1300°C was very regular and dense, above 96% of theoretical density (5.9 g/cm3). Al4C3 was observed in the NiAl consolidated at 1300°C by TEM analysis. It is thought that the carbons came from the stearic acid
during the MA process and the graphite mold during the PAS process. The grain size of the NiAl consolidated at 1300°C did
not increase but the grain shape became flat due to compressive force. 相似文献
15.
Synthesis and characterization of nanocrystalline AlFeTiCrZnCu high entropy solid solution by mechanical alloying 总被引:3,自引:0,他引:3
Traditional alloys are based on one or two major alloying elements. High entropy alloys are equiatomic multicomponent alloys, wherein configurational entropy is maximized to obtain single phase solid solutions. The present paper reports synthesis of nanostructured equiatomic high entropy solid solutions from binary to hexanary compositions in Al–Fe–Ti–Cr–Zn–Cu system by mechanical alloying. These alloys have BCC structure with crystallite size less than 10 nm. The high entropy solid solution in these alloys is stable even after annealing at 800 °C for 1 h. The hardness of AlFeTiCrZnCu solid solution is 2 GPa in the sintered condition with a density of 99%. The similar nanostructured solid solutions have also been synthesized in CuNiCoZnAlTi and NiFeCrCoMnW alloys. 相似文献
16.
J. Safari G.H. Akbari A. ShahbazkhanM. Delshad Chermahini 《Journal of Alloys and Compounds》2011,509(39):9419-9424
The effect of milling time on the microstructure and mechanical properties of Al and Al-10 wt.% Mg matrix nanocomposites reinforced with 5 wt.% Al2O3 during mechanical alloying was investigated. Steady-state situation was occurred in Al-10Mg/5Al2O3 nanocomposite after 20 h, due to solution of Mg into Al matrix, while the situation was not observed in Al/5Al2O3 nanocomposite at the same time. For the binary Al-Mg matrix, after 10 h, the predominant phase was an Al-Mg solid solution with an average crystallite size 34 nm. Up to 10 h, the lattice strain increased to about 0.4 and 0.66% for Al and Al-Mg matrix, respectively. The increasing of lattice parameter due to dissolution of Mg atom into Al lattice during milling was significant. By milling for 10 h the dramatic increase in microhardness (155 HV) for Al-Mg matrix nanocomposite was caused by grain refinement and solid solution formation. From 10 to 20 h, slower rate of increasing in microhardness may be attributed to the completion of alloying process, and dynamic and static recovery of powders. 相似文献
17.
L.Yu. Pustov V.V. Tcherdyntsev Sh.M. Abdulhalikov S.D. Kaloshkin E.V. Shelekhov E.I. Estrin Yu.V. Baldokhin 《Journal of Alloys and Compounds》2009,483(1-2):200
Ternary Fe86NixMn14−x alloys, where x = 0, 2, 4, 6, 8, 10, 12, 14, 16 at.%, were prepared by the mechanical alloying (MA) of elemental powders in a high-energy planetary ball mill. X-ray diffraction analysis and Mössbauer spectroscopy were used to investigate the structure and phase composition of samples. Thermo-magnetic measurements were used to study the phase transformation temperatures. The MA results in the formation of bcc α-Fe and fcc γ-Fe based solid solutions, the hcp phase was not observed after MA. As-milled alloys were annealed with further cooling to ambient or liquid nitrogen temperatures. A significant decrease in martensitic points for the MA alloys was observed that was attributed to the nanocrystalline structure formation. 相似文献
18.
In the present work an elemental powder mixture of Al60Fe15Si15Ti10 (at.%) was mechanically alloyed in a high-energy ball mill. A part of the milling product was examined in a calorimeter, while another portion was subjected to consolidation by hot-pressing at 1000 °C for 180 s under a pressure of 7.7 GPa. The results obtained show that a nanocrystalline cubic phase with the lattice parameter a0 = 11.645 Å, isomorphous with the τ2 (Al2FeTi) phase, is formed during mechanical alloying process. Heating of the milling product in the calorimeter up to 720 °C causes limited growth of grains, however the τ2 phase remains nanocrystalline with the mean crystallite size of 28 nm. Grain growth takes place during consolidation of the milling product as well, although the τ2 phase remains nanocrystalline with the mean crystallite size of 34 nm. The microhardness of the bulk nanocrystalline sample is 1013 HV0.2 and its open porosity is 0.3%. The results obtained show that the quality of compaction with preserving nanometric grain size of the τ2 phase is satisfactory and its microhardness is relatively high. 相似文献
19.
NiAl intermetallic has been produced by mechanical alloying in a high energy vibrator mill using elemental Ni and Al powder mixture. The NiAl powders were formed in two ways. One by a gradual exothermic reaction mechanism during a long time continuous milling and the other by explosive exothermic reaction mechanism that occurred when opening the milling vessel to the air atmosphere after a short time milling. Prolonged milling for both cases resulted in change of morphology and refinement of grain size down to nano scale. 相似文献
20.
Synthesis of TiB2 nanocrystalline powder by mechanical alloying 总被引:2,自引:2,他引:0
1 Introduction TiB2 has been widely used in some industrial fields owing to its high melting temperature, hardness, elastic modulus, electro-conductibility and thermal diffusivity, and excellent refractory properties and chemical inertness. Usually, TiB2… 相似文献