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1.
The crystallization behaviour of amorphous Fe93 – x
Zr7B
x
(x = 3, 6, 12 at.%) alloys, the microstructures of the primary crystallization products of stable and metastable phases and the subsequent transformations, have been studied using a combination of differential scanning calorimetry, differential thermal analysis, X-ray diffraction and transmission electron microscopy, including microdiffraction. It has been found that, for x = 3 and 6 at.%, the sole product of primary crystallization is the bcc -Fe phase and the average grain sizes of the crystalline phase were 14 nm and 12 nm for the two alloys, respectively. However, when x = 12 at.%, primary crystallization results in more than one crystalline phase, and a metastable phase with the cubic Fe12Si2ZrB structure is the major crystallization product after the primary crystallization reaction, accompanied by the -Fe phase. The average grain size of this metastable phase was 35 nm for the alloy heated to 883 K at 20 K/min. Isothermal heat treatments at 873 K and 973 K confirm that after being heated for 240 h, this metastable phase transforms into equilibrium phases: bcc -Fe, hcp ZrB2 and probably hcp Fe2Zr. The apparent activation energies for the primary crystallization reaction during continuous heating for these three alloys are 4.4 ± 0.2 eV, 3.5 ± 0.2 eV and 6.9 ± 0.3 eV, respectively. 相似文献
2.
The crystallization process of amorphous Fe80B20–x
Si
x
(x=0, 2, and 8) ferromagnetic alloys has been studied by using 57Fe Mössbauer spectroscopy and X-ray diffraction studies. Results for samples heat treated at different temperatures for different times show that the crystallization of Fe80B20–x
Si
x
samples having x=0 and 2 leads to -Fe and t-Fe3B, while for x=8, it leads to -Fe, t-Fe2B, and perhaps Fe-Si. It is further observed that the addition of silicon to the Fe-B system improves the thermal stability of the system. 相似文献
3.
Ultrafine (Fe0.7Co0.3)100–x
B
x
amorphous powders with boron contentx in the range 27–40 at % have been prepared by borohydride reduction. The preparation process shows that the powders have a catalysis property. The results of X-ray and electron diffractions show that all of the samples were spherical amorphous particles of dimension <0.2 m. The difference in the ease of composition between Fe-Co-B powder and ribbon indicates that the local environment of Fe-Co-B powder may be different from that of Fe-Co-B ribbon. The study of crystallization behaviour using Mössbauer, X-ray and differential scanning calorimetry measurements indicates that there are two steps in the crystallization process. These steps represent the formation of -Fe70Co30 phase and Fe2B-like phase, respectively. 相似文献
4.
Makoto Matsuura 《Journal of Materials Science》1986,21(6):2207-2211
The crystallization kinetics of the melt-spun Fe-Zr metallic glasses in the iron-rich region has been investigated by means of DSC and X-ray diffraction. The crystallization mode changes with iron concentration. In the lower iron region, 20 x 25, the Fe
x
Zr100–x glasses crystallize into -Zr and Ti2Ni-type FeZr2 with an accompanying sharp and large exotherm at the first crystallization step and immediately after this step, they transform into orthorhombic FeZr3. On the other hand, the alloys with 35 x 40 exhibit a gradual exotherm which initiates from a temperature far below the definite crystallization temperature (T
x). The Fe-Zr metallic glasses in this concentration region crystallize polymorphously into the oxygenstabilized Ti2Ni-type FeZr2 with accompanying relatively small and composite exotherms. The annealing at a temperature where the gradual exotherm occurs for the alloys with 30 x 40 does not cause any changes of X-ray halo pattern but results in the reduction of the heat of exotherm due to the crystallization. 相似文献
5.
The microstructures and kinetics with heating for an amorphous Fe78B13Si9 alloy were studied by X-ray diffraction, transmission electron microscopy, differential thermal analysis and differential scanning calorimetry. The first crystallization takes place by the simultaneous formation of -(Fe,Si) and Fe3B having the shapes of dendrite and spherulite, respectively. Metastable Fe3B then transformed into a stable phase of Fe2B at a higher temperature. The activation energy for crystallization and the Avrami exponent were determined. It was found that crystallization behaviour in Fe78B13Si9 is controlled by nucleation rather than growth. 相似文献
6.
The infrared reflectance and transmission spectra of amorphous CdGe
x
As2 were investigated to study the amorphous structure with varying Ge content. The mid-infrared optical absorption edges of amorphous CdGe
x
As2 with 0<x<1.2, were observed in the range 1.6–1.7 m, indicating a structural similarity in short-range order throughout. Comparing the reflectance and transmission spectra of amorphous and devitrified crystalline phases established that the structures of amorphous CdGe
x
As2 transformed from the CdAs2 basic structure to the chalcopyrite (CdGeAs2) structure, as one progressed fromx=0 tox=1.2. The infrared spectra were interpreted interactively with radial distribution function, magnetic susceptibility, density measurements, and crystallization studies. The crystallization behaviour of amorphous CdGe
x
As2 that was heat treated at different temperatures was investigated using far-infrared transmission spectra. 相似文献
7.
K. P. Mizgalski O. T. Inal F. G. Yost M. M. Karnowsky 《Journal of Materials Science》1981,16(12):3357-3364
The crystallization behaviour of the Metglas 2826 MB alloy (Fe40Ni38Mo4B18) has been studied using resistance measurements and X-ray diffraction techniques. Three annealing sequences were used to follow the process. Samples were annealed isothermally (a) at 780° C in a vacuum of 2×10–5 torr for times in the range 1 sec to 4 h, (b) for 2 h in an argon atmosphere at temperatures where the resistance curve indicated phase changes to occur, and (c) for 300 h in 100 torr of helium at 400, 600, 700 and 850° C. From these annealing sequences it was found that the alloy did not crystallize below 410° C and followed a crystallization process of: amorphous Fe40Ni38Mo4B18 Fe
x
Ni23–x
B6 (cubic)+glassy matrix Fe
x
Ni23–x
B6+(Fe, Ni) (FCC) (Fe, Ni)3B(bct). This series of transformations was followed for Sequences (a) and (c) above, but was slightly different for Sequence (b). An orthorhombic (Fe, Ni)3 B phase was found in the samples annealed in a vacuum of 2×10–5 torr.Trademark of Allied Chemical Co. 相似文献
8.
Mechanical alloying was used to synthesize NixZr1–x alloys from mixtures of intermetallic compound powders, and also from mixtures of intermetallic compound powders and pure elemental powders. The mechanically alloyed powders were amorphous in the range 0.24 x 0.85. This range is larger than amorphous alloys produced by the melt-spinning technique and mechanical alloying of elemental crystalline powders. Two-phase mixtures of the amorphous phase and the corresponding crystalline terminal solid solution were formed in the range 0.10 x 0.22, and x=0.90. It is found that the morphological development during mechanical alloying of these powders is different from mechanical alloying using only pure ductile crystalline elemental powders. The thermal stability has been investigated. The enthalpy and activation energy of crystallization for Ni-Zr amorphous powders prepared by mechanical alloying are lower than those for melt-spun samples of the same composition. The crystallization temperature of the mechanically alloyed Ni-Zr amorphous powders is higher than that of meltspun samples in the composition range Ni20Zr80 to Ni33Zr67 and Ni40Zr60 to Ni60Zr40. The presence of tiny crystallites as nucleation centres and high oxygen levels in the mechanically alloyed amorphous alloys might be responsible for the differences in crystallization behaviour. A new crystalline metastable phase was observed during crystallization studies of Ni24Zr76 amorphous powder. 相似文献
9.
D. S. Easton C. G. McKamey D. M. Kroeger O. B. Cavin 《Journal of Materials Science》1986,21(4):1275-1279
Metallic glass alloys of Ni-Zr were prepared by vapour and liquid quenching. For glass compositions at and near 60 at% Zr, crystallization proceeded by the sequence: amorphous metastable crystalline phase NiZr2 + NiZr. The metastable Ni40Zr60 phase exhibited a very distinctive X-ray diffraction pattern and was present in both liquid- and vapour-quenched samples. Long-term anneals of samples with the metastable structure produced the equilibrium phases NiZr2 and NiZr. The crystallization of the amorphous structure directly to a single metastable phase shows a correspondence between the compositions of the amorphous and crystalline phases. These results thus suggest a connection between the short-range structure of the glassy phase and the crystalline phases to which they transform. An observation of peaks and valleys in a plot of the X-ray scattering vector,Q
p, against glass composition is noted. 相似文献
10.
Tetsuo Soumura Shigeru Saito Kenichiro Takeda Takao Maeda 《Journal of Materials Science》1986,21(12):4245-4249
The structure of amorphous (Fe1–x
Mn
x
) alloys prepared by a single roller technique has been investigated in terms of X-ray diffraction and electrical resistance. The lattice parameter of the crystalline precipitates, which were-Fe and b c t (FeMn)3B, was determined under different heat treatments. On heating up to 440° C where a mixture of amorphous and crystalline phases exists and up to 550° C corresponding to the completion of crystallization, the lattice parameter of the-Fe phase rises to that of pure-Fe with increasing manganese concentration. In samples annealed at 660° C for 5 h, the opposite behaviour is observed. These results can be explained on the basis of the position of the boron atom occupying the-Fe lattice, the pressure effect exerted by the environment, and the enhancement of the chemical short-range ordering between manganese and boron atoms with manganese concentration. In the b c t phase, which shows a reduction in lattice parameter with manganese concentration independent of heat treatment, the effect of redistribution of the atoms in the unit cell should be also taken into account. 相似文献
11.
Wen Li C. X. Xie Y. Z. Yang C. L. Yao 《Journal of Superconductivity and Novel Magnetism》2018,31(9):2805-2809
High-iron Fe–Zr–Si amorphous ribbons were fabricated through the melt-spun technique. Then, the effects of Si content on the glass-forming ability and magnetic properties of Fe90?xZr10Six (x =?1, 2, 3, 4, 5, 10) alloys were investigated. Results showed that the amorphous structure only formed in an alloy composition of 3 at.% Si. Moreover, α-Fe(Si) and Fe3Zr phase appeared gradually when Si was added. Fe87Zr10Si3 alloy is a unique amorphous structure in Fe90?xZr10Six ribbons. The peak temperatures of the two crystallization stages were 464 and 600 °C. The saturation magnetization (Ms) values of the alloys ranged from 91.2 to 132.3 emu/g, and all had an initial increase before decreasing and their coercivity (Hc) values increased with increased Si content. The Fe87Zr10Si3 amorphous alloy exhibited a low Hc value of approximately 39.1 A/m, which shows good magnetic properties in the as-quenched state. After annealing, the Ms of the amorphous sample considerably improved, particularly reaching 165.3 emu/g at 600 °C. 相似文献
12.
Amorphous Fe-17 at %B alloy prepared by a splat-quenching technique was annealed at temperatures ranging from 250 to 500° C for different periods. A time-temperature transformation diagram has been constructed from X-ray diffraction examination of annealed samples. On annealing the alloy at a pressure of 50 kbar, an appreciable retardation of crystallization was observed. The crystalline phase precipitated first from the amorphous matrix at 1 bar. This was -Fe containing a small amount of boron, but at 50 kbar this was a mixture of -Fe(B) and intermetallic phase Fe3B. Under the increased pressure of 100 kbar the mode of the crystallization was further changed and Fe3B became the first precipitating phase. Preferential formation of Fe3B under pressure can be explained assuming a modified dense-random packing model for the amorphous structure.On leave from Institute of Physics, Academia Sinica, Beijing, China. 相似文献
13.
Microstructural changes in Fe73.5–xCrxCu1Nb3Si13.5B9 (0x5) alloys with thermal treatment were studied by electron microscopy. In a first stage, around 800 K, an Fe(Si) nanocrystalline phase is formed in the amorphous residual matrix. Crystallization onset is enhanced with the Cr content of the alloy. In a second stage, around 950 K, full crystallization of the samples leads to the formation of a body centred cubic (b.c.c.) boride-type unknown crystal phase with a lattice parameter of a=1.52 nm, and recrystallization of the previous Fe(Si) nanophase also occurs. No qualitative differences were found between dynamic and isothermal crystallization. The size effect for thin samples is limited to a lowering of crystallization temperatures. For isothermal nanocrystallization in the temperature range 775–900 K, the mean grain size of the nanocrystals increases for short annealing times to stabilize at a constant value of about 10–15 nm for long annealing times. The stabilized grain size increases with increasing annealing temperature and slightly decreases with the Cr content of the alloy. 相似文献
14.
Thin film samples of molybdenum were electron-beam evaporated at 80 K in a 6.6×10–4 Pa partial pressure of nitrogen and subsequently analysed for structure, superconductivity and crystallization behaviour. X-ray diffraction of as-deposited samples showed a typical amorphous structure and fcc and bcc phases upon heating. A superconducting transformation at 7.0 to 7.2 K was detected by the resistivity technique. Isothermal DSC scans obtained for a range of temperatures were calibrated and integrated to produce transformed volume (x)-time data. All plots of In [-In (1–x)] against Int have two linear regions with slopes ofn
13.6 for 0<x<0.5 andn
2 2.0 for 0.7<x<1; wheren is the principal parameter in the Johnson-Mehl-Avrami theory of the crystallization transformation. The relationship of this binary pattern of crystallization to the observation of two apparent crystallization peaks in dynamic DSC scans of several samples of electron-beam deposited Mo-N and to the appearance of both Mo-bcc and Mo2N-fcc phases in the X-ray patterns of the crystallized samples is discussed. Possible patterns of simultaneous or successive modes of nucleation and growth, including combinations of varying nucleation rates, different dimensionals of growth, and interfacial and diffusion controlled growth, are considered. 相似文献
15.
A. M. Sanad I. Kashif A. M. Abou-Al-Azm M. A. Khaled H. Farouk 《Journal of Materials Science》1986,21(1):230-234
A glass system was prepared according to the formula 75 mol % B2O3-(25 –x) mol % BaO –x mol % Fe2O3, wherex = 0, 1, 2.5, 5, 7.5 and 10. The glasses were subjected to heat treatment at 550° C for 2, 6, 12, 18 and 24 h. The glasses were also irradiated using-rays at a dose of 4.805 × 104 rad h–1 for 12, 18 and 24 h. An X-ray diffraction technique was used to identify the separated crystalline phases. The electrical conductivity and activation energy of untreated, heat-treated and irradiated samples were measured and calculated. The rate and the dimensions of crystallization were also calculated by using the Avrami equation. It was found that-Fe2O3 is the separated phase when a sample containing 7.5 mol% Fe2O3 is heat treated for 24h;-Fe2O3 and Fe2O3 are the separated phases when the sample containing 10 mol% Fe2O3 is heat treated for 6, 12 and 18 h, with the addition of BaO when the sample is heat treated for 24 h. A miminum value for the electrical conductivity of glass samples was found to occur around an Fe2O3/BaO ratio of 0.425. The rate of crystallization in the sample containing 10 mol% Fe2O3 is 1.30607 × 10–3 and the geometry of crystallizationn is 1.2238, which indicates that the crystallization was in one dimension. 相似文献
16.
M. V. Tsodikov O. V. Bukhtenko O. G. Ellert V. M. Shcherbakov D. I. Kochubey 《Journal of Materials Science》1995,30(4):1087-1094
As a result of titanium and zirconium alcoholates hydrolysis in the presence of dissolved Fe(acac)3, amorphous iron-containing gels have been synthesized. Their heat treatment has led to polycrystalline double oxides Fe
x
Zr1–0.75x
O2– (C) and Fe
x
Ti1–0.75x
O2– (T) formation. It has been shown that oxides (C) and (T) are likely to be solid solutions with 0.01<x<0.17 and 0.01<x<0.14, respectively. On the basis of X-ray diffraction and extended X-ray absorption fine structure data, iron-zirconium and iron-titanium crystallite models for gels and oxides have been proposed. It has been found that the crystallization process does not lead to a significant change in interatomic distances typical for local structures detected in gels. 相似文献
17.
G. J. Van Der Kolk T. Minemura J. J. Van Den Broek 《Journal of Materials Science》1989,24(5):1895-1900
Binary alloys of the systems V-Pd, Nb-Pd and Ta-Pd were vapour deposited and investigated by transmission electron microscopy. The atomic fraction,x, was varied in steps of 0.1 from one pure element to the other. The range over which an amorphous phase is observed is found to increase in width going from 3d to 5d alloying element in palladium: the compositions where amorphous phases are found are V1–x
Pd
x
(x = 0.5), Nb1–x
Pd
x
(x = 0.4 to 0.6) and Ta1–x
Pd
x
(x = 0.2 to 0.6). The composition range over which a crystalline phase is found correlates well with the single-phase solid solution region close to the melting temperature in the phase diagram. Crystallization of the V0.5Pd0.5 alloy takes place at 550 K. The amorphous Nb1–x
Pd
x
(x = 0.4, 0.5) films crystallize at 850 K, whereas the amorphous Ta-Pd films crystallize between 850 and 1050K, depending on the composition. For Nb1–x
Pd
x
(x = 0.4 to 0.5) and Ta1–tx
Pd
x
(x = 0.2 to 0.6) primary crystallization takes place into an f c c phase. The second crystallization step leads to a phase with a complex structure. The result is a two-phase system. V0.5Pd0.5 and Nb0.4Pd0.6 crystallize polymorphically to an f c c solid solution. The crystallization temperatures for the compositions which display primary crystallization are higher than for the compositions which crystallize by a polymorphic reaction. 相似文献
18.
A detailed study of the process of crystallization in amorphous Fe25Sc75, Fe28 Sc72 and Fe25Sc45Zr30 alloys has been carried out using differential scanning calorimetry, X-ray diffraction and Mössbauer spectroscopic techniques. The complex multi-stage transformation process in Fe25Sc75 and Fe28Sc72 is understood in terms of polymorphous formation of an intermediate metastable crystalline phase of orthorhombic structure (a = 0.521 nm, b = 0.648 nm and c = 1.212 nm) and of likely Sc3Fe stoichiometry, before final eutectic crystallization to stable Fe2Sc and -Sc. 相似文献
19.
Sang Hoon Yoon Dan Liu Dongna Shen Minseo Park Dong-Joo Kim 《Journal of Materials Science》2008,43(18):6177-6181
The effect of chelating agents of ZnO precursor solutions on crystallization behavior was investigated. Two different additives,
monoethanolamine (MEA) and diethanolamine (DEA), and crystalline Pt (111)/Si and amorphous SiN
x
/Si substrates, were used for this study. ZnO film grown on SiN
x
/Si from a DEA-chelated precursor solution shows a poorly oriented microstructure with weak crystallization peaks, while ZnO
film grown on Pt(111)/Si shows a c-axis preferred orientation. In the case of ZnO films prepared with a MEA-chelated precursor
solution, all films show a strong preferred orientation irrespective of substrate type. This result clearly demonstrates the
role of the chelating agent on the crystallographic orientation and crystallization behavior of sol-gel processed ZnO films. 相似文献
20.
A new technique has been used for the early stages of crystallization of amorphous materials, like metallic alloys. In situ X-ray diffraction has been performed during the early stages of crystallization of Fe80B20. The samples are resistively heated to 600°C in a customized vacuum chamber. A programmable charge-coupled device detector records simultaneously the evolution of the three phases: -Fe, Fe3B and Fe2B in the minute scale. This is the first in situ X-ray diffraction study of this system in these temperature and time scales. Interesting behaviours have been seen: appearance and disappearance of phases, -Fe supersaturation solution in boron (found for the first time in this compound), and migration of B out of the -Fe matrix. The two-dimensional diffraction pictures show topography irregularities indicating crystallite inhomogeneties. 相似文献