共查询到20条相似文献,搜索用时 31 毫秒
1.
《Intermetallics》2006,14(8-9):1027-1032
We observed quasicrystal-to-amorphous-to-crystal (Q–A–C) transition in Zr66.7Pd33.3 metallic glass. The unique disordering–ordering phase transition was induced by 2 MeV electron irradiation at 298 K. Electron irradiation can induce not only the solid-state amorphization but also crystallization of a glassy structure under the same irradiation conditions. The Q–A–C transition can be explained by change in the phase stability of crystal, quasicrystal and amorphous phases by electron irradiation induced atomic displacement. 相似文献
2.
《Intermetallics》2007,15(2):211-224
Electron irradiation induced phase transformation behavior of an amorphous phase in Zr66.7Ni33.3 alloy, and an amorphous phase or supercooled liquid in Zr60Al15Ni25 alloy was investigated. The amorphous phase could not maintain the original glassy structure under electron irradiation at 298 K, and f.c.c.-solid solution precipitated under electron irradiation in both alloys. The precipitation of C16-Zr2Ni, big-cube (metastable f.c.c.-based Zr2Ni intermetallic compound), Zr6Al2Ni and Zr5AlNi4 crystalline phases from an amorphous phase was not observed during electron irradiation induced crystallization. The amorphous phase in Zr60Al15Ni25 metallic glass shows the highest phase stability against electron irradiation induced crystallization among Zr66.7Cu33.3, Zr66.7Ni33.3, Zr65Al7.5Ni27.5, Zr60Al15Ni25 and Zr65Al7.5Ni10Cu17.5 alloys. In Zr60Al15Ni25 metallic glass, electron irradiation promoted the precipitation of f.c.c.-solid solution and Zr6Al2Ni crystalline phases from the supercooled liquid. 相似文献
3.
《Scripta materialia》2003,48(9):1237-1242
Effect of electron irradiation on structural change of Zr66.7Cu33.3 alloy was examined. Metastable nanocrystalline f.c.c.-Zr2Cu phase precipitated from the amorphous phase by electron irradiation, while b.c.t.-Zr2Cu phase was crystallized by thermal annealing. The crystalline b.c.t.-Zr2Cu phase was transformed to the nanocrystalline f.c.c.-Zr2Cu phase through the amorphous state during electron irradiation. 相似文献
4.
Phase selection in electron-irradiation-induced crystallization and crystal-to-amorphous-to-crystal (C–A–C) transition at 298 K in quasicrystal-forming Zr–Pt metallic glass alloys were investigated. Two types of f.c.c. nano-crystalline precipitates were formed in amorphous Zr80Pt20 and Zr66.7Pt33.3 alloys under electron irradiation; such unique nano-crystalline structures were not observed during thermal annealing. It was inferred that unique phase selection in electron-irradiation-induced crystallization and thermal crystallization can be explained by the large negative chemical mixing enthalpy (ΔHchem) in Zr–Pd and Zr–Pt alloys. 相似文献
5.
《Acta Materialia》2000,48(15):3985-3996
The influence of oxygen on the crystallization behavior of Zr65−xCu27.5Al7.5Ox (x=0.14, 0.43 and 0.82) and Zr66.7−xCu33.3Ox (x=0.14 and 0.82) metallic glasses has been studied. The supercooled liquid regime (ΔTx) decreases with increase in oxygen content for the Zr–Cu–Al alloy, while it increases for the Zr–Cu metallic glass. In the case of the Zr–Cu metallic glass, the crystallization product (Zr2Cu) is not influenced by the oxygen content, while in Zr–Cu–Al alloys the oxygen level has a strong influence on the crystallization sequence. At low oxygen level (x=0.14), the ternary glass crystallizes polymorphously to Zr2(Cu,Al). At higher oxygen content, the ternary amorphous alloy crystallizes in two stages by primary crystallization into an icosahedral phase and subsequently to the stable Zr2(Cu,Al) phase. Three-dimensional atom probe results have shown that the composition of the icosahedral and amorphous phases is close to Zr75Cu15Al5O5 and Zr62Cu24Al14, respectively. 相似文献
6.
本文通过x射线衍射(XRD)、差示扫描量热法(DSC)和透射电子显微镜(TEM)研究了退火温度对Zr48Cu36Ag8Al8金属玻璃微观结构演化的影响。结果表明,快速凝固获得的样品为典型的非晶态结构。当样品在703K保温20分钟时,均一的非晶基体相分离成两种非晶合金,即,发生相分离。由于相分离结构与非晶基体在等温退火过程是竞争的关系,这个结构很容易向晶化态进行转变,形成AlZr2 AlAg3相。Zr48Cu36Ag8Al8金属玻璃的微观结构在过冷液相区等温退火过程中经历了的局部结构转变,相分离以及纳米晶转变,这个过程意味着Zr48Cu36Ag8Al8金属玻璃的微观结构对退火温度十分敏感。此外,相分离的形成可以加速纳米晶的形成。 相似文献
7.
M. L. Vaillant T. Gloriant I. Thibon A. Guillou V. Keryvin T. Rouxel D. Ansel 《Scripta materialia》2003,49(12):1139-1143
Dendritic crystals, randomly distributed into the as-quenched Zr55Cu30Al10Ni5 bulk metallic glass were characterized by optical microscopy, electron probe microanalysis, X-ray diffraction and electron backscattering diffraction. Oxygen enrichment is observed into these crystallites (formula: Zr7Cu4Al3O, space group: Fd
m, cell parameter: 5.70 Å) demonstrating the negative effect of oxygen, inducing partial crystallization during casting. 相似文献
8.
T. Czeppe A. Sypien A. Wierzbicka-Miernik 《Journal of Materials Engineering and Performance》2016,25(12):5289-5301
The article presents investigations of Ti40Cu36Zr10Pd14 bulk metallic glass crystallization process heated with the rates of 10, 60, 100 and 140 K/min. High heating rates experiments were performed in a new type of differential scanning calorimeter equipped with a fast responding thermal sensor. Phase composition and microstructure were studied with x-ray diffraction and transmission electron microscopy. The observed crystallization proceeded in two separate steps. Applied high rates of heating/cooling resulted in the crystallization of only one CuTi phase, replacing typical multi-phase crystallization. The microstructure after crystallization was polycrystalline with some amount of amorphous phase retained. Kinetic parameters were determined with the use of the Kissinger and Friedman iso-conversional analysis and Matusita–Sakka iso-kinetic model. The kinetic analysis supplies results concerning autocatalytically activated mechanism of primary crystallization with decreasing activation energy and small density of quenched-in nuclei, in good agreement with previous structural investigations. The mechanism of secondary crystallization required dense nuclei site, increasing activation energy and large nucleation frequency. The amorphous phase of Ti40Cu36Zr10Pd14 BMG revealed high thermal stability against crystallization. Application of high heating rates in DSC experiments might be useful for the determination of mechanism and kinetic parameters in investigations of metallic glasses crystallization, giving reasonable results. 相似文献
9.
The crystallization process of Pd74Si18Au8 amorphous alloy has been investigated by transmission electron microscopy, small angle X-ray scattering and three-dimensional atom probe techniques. Although literature suggests that the alloy decomposes into two glassy phases prior to the crystallization, we found that the crystallization occurs directly from a single amorphous phase by the primary crystallization of fcc Pd–Au solid solution, followed by the polymorphous crystallization of the remaining amorphous phase to a Pd3Si phase. 相似文献
10.
设计了一种非晶合金摩擦焊装置,以Zr41Ti14Cu12.5Ni10Be22.5非晶棒料为研究对象,进行了摩擦焊试验.焊接样品经SEM,XRD,维氏硬度、TEM等检测,结果显示焊接界面无明显未熔合,样品仍然保持非晶态,接头硬度总体增大,接头处出现了纳米晶.采用ANSYS软件对非晶合金摩擦焊的温度场进行仿真.结果表明,在摩擦时间t=0.25s时摩擦界面中心温度超过非晶棒料玻璃转变温度,接触面全部进入过冷液相区,应进行顶锻.仿真结果与摩擦焊试验结果基本吻合,有利于指导焊接试验. 相似文献
11.
W.K. An X. Xiong Y. Liu J.H. Li A.H. Cai Y. Luo T.L. Li X.S. Li 《Journal of Alloys and Compounds》2009,486(1-2):288-292
The glass forming ability, thermal stability and non-isothermal crystallization kinetics of Zr63.5Al10.7Cu10.7Ni15.1 glass forming alloy were investigated. Its maximum glass forming dimension is up to 6 mm and its critical cooling rate is less than 40 K s−1. It manifests two crystallization procedures and the second crystallization peak is more sensitive to heating rate than the first crystallization peak. The glass transition and crystallization both have remarkable kinetics effects. The ms fitted by Arrhenius and VF equations are consistent with each other. Small m value about 17 indicates better thermodynamic stability and GFA of Zr63.5Al10.7Cu10.7Ni15.1. 相似文献
12.
Sophie NowakLoïc Perrière Lucas DembinskiSandrine Tusseau-Nenez Yannick Champion 《Journal of Alloys and Compounds》2011,509(3):1011-1019
Spark plasma sintering (SPS) was used to sinter gas-atomized Zr57Cu20Al10Ni8Ti5 amorphous powder. Systematic analyses were performed to study particle size and annealing time effects on the parts structure and properties. Partial devitrification and particles welding were observed and correlated to particle size and thermal conditions. Mechanical testing, through compression and micro-hardness, reveals that the sintered parts show strength similar to a quenched bulk metallic glass and damaging before failure. However, the pulsed current input does not seem the most relevant way to sinter amorphous powders: during the sintering initial stages (when necks are small), excessive over-heating is generated in the vicinity of particles necks, and is responsible for partial devitrification; further current input at large necks leads to complete densification. Effects of the stress, the thermo- and electro-transports on the sintering are evaluated to provide a better understanding of the SPS mechanisms of densification of metallic glasses. 相似文献
13.
Guoqiang Xie Dmitri V. Louzguine-Luzgin Qingsheng Zhang Wei Zhang Akihisa Inoue 《Journal of Alloys and Compounds》2009,483(1-2):24
The crystallization kinetics and structure changes in a melt-spun Cu50Zr45Ti5 glassy alloy on heating were investigated by X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry and differential isothermal calorimetry. The glassy phase in the Cu50Zr45Ti5 alloy was crystallized forming Cu10Zr7 and CuZr2 phases upon thermal annealing. The activation energy for crystallization obtained by the Arrhenius equation was 435 kJ/mol. The crystallization process took place by nucleation and growth mechanism, and an Avrami exponent of about 3.3 may indicate a three-dimensional interface-controlled growth of nuclei with a decreasing nucleation rate. 相似文献
14.
M. Sherif El-Eskandarany A. A. Bahgat N. S. Gomaa N. A. Eissa 《Journal of Alloys and Compounds》1999,290(1-2)
A single phase amorphous Fe52Nb48 alloy has been synthesized through a solid state interdiffusion of pure polycrystalline Fe and Nb powders at room temperature, using a high-energy ball-milling technique. The mechanisms of metallic glass formation and competing crystallization processes in the mechanically deformed composite powders have been investigated by means of X-ray diffraction, Mössbauer spectroscopy, differential thermal analysis, scanning electron microscopy and transmission electron microscopy. The numerous intimate layered composite particles of the diffusion couples that formed during the first and intermediate stages of milling time (0–56 ks), are intermixed to form amorphous phase(s) upon heating to about 625 K by so-called thermally assisted solid state amorphization, TASSA. The amorphization heat of formation for binary system via the TASSA, ΔHa, was measured directly as a function of the milling time. Comparable with the TASSA, homogeneous amorphous alloys were fabricated directly without heating the composite multilayered particles upon milling these particles for longer milling time (86 ks–144 ks). The amorphization reaction here is attributed to the mechanical driven solid state amorphization. This single amorphous phase transforms into an order phase (μ phase) upon heating at 1088 K (crystallization temperature, Tx) with enthalpy change of crystallization, ΔHx, of −8.3 kJ mol−1. 相似文献
15.
E. Matsubara T. Ichitsubo K. Itoh T. Fukunaga J. Saida N. Nishiyama H. Kato A. Inoue 《Journal of Alloys and Compounds》2009,483(1-2):8
Heating rate dependence of glass transition and crystallization temperatures is applicable for evaluation of glass structural stability and also for discussion on the apparent activation energies for glass transition and crystallization. The glass-structure stabilities of the Zr-based BMGs (Zr50Cu40Al10, Zr70Cu20Al10 and Zr70Ni20Al10) and the conventional amorphous alloys (Zr70Cu30 and Zr70Ni30) are assessed by the densely packed glass structure as well as the complicated crystallization process. By the reverse Monte Carlo (RMC) simulation with X-ray and neutron diffraction data, it is shown that the densely packed structure is built by icosahedron-like clusters. In Zr65Al7.5Ni10Pd17.5 and Zr65Al7.5Ni10Cu17.5, the effect of Pd atoms on the glass structure is also described. 相似文献
16.
N. Ismail A.A. El-Meligi M. Uhlemann A. Gebert J. Eckert L. Schultz 《Journal of Alloys and Compounds》2009,480(2):321-324
Amorphous materials of Zr–Cu–Ni–Al systems have shown attractive electrochemical hydrogen absorption properties. A comparison between Zr60Cu15Al10Ni10Pd5 and Zr65Cu17.5Al7.5Ni10 reveals that the palladium (Pd) increases the hydrogen absorption capacity. Charging melt-spun Zr60Cu15Al10Ni10Pd5 ribbons electrochemically to different hydrogen-to-metal (H/M) ratios and following the effusion of hydrogen by thermal desorption analysis (TDA) reveals hydrogen desorption from interstitial sites of high energy levels at temperatures below 630 K. Zirconium hydrides are formed above 630 K. At higher temperatures partial desorption of hydrogen occurs. The thermal stability observed with differential scanning calorimetry (DSC) of the amorphous phase has been significantly deteriorated by hydrogen absorption. After hydrogenation, the crystallization behaviour shows suppression of the characteristic quasicrystalline phase and depends on the hydrogen content. Therefore, at low hydrogen concentrations H/M = 0.3, Cu and/or Cu-rich phases are primarily formed while at high hydrogen concentrations H/M ≥ 0.9 Zr-hydride phase(s) are mainly formed. 相似文献
17.
Guoqiang Xie Lin ShaoDmitri V. Louzguine-Luzgin Akihisa Inoue 《Surface & coatings technology》2011,206(5):829-833
Partial nanocrystallization induced by ion irradiation can be used to improve the surface properties in metallic glasses. We investigated the crystallization behavior and the structure of the formed nanocrystalline phases in a melt-spun Cu50Zr45Ti5 glassy alloy irradiated with 140 keV He ions to a fluence of 1.7 × 1017/cm2. Crystalline nanoparticles were precipitated by He ion irradiation. The nanocrystalline phases were identified as a mixture of the orthorhombic Cu10Zr7 phase, tetragonal CuZr2 phase and monoclinic CuZr phase. Hardness enhancement was observed at a depth close to the projected range of the He ions, which was related to the formation of the crystalline nanoparticles. 相似文献
18.
Vincent Keryvin Marie-Laure Vaillant Tanguy Rouxel Marc Huger Thierry Gloriant Yoshihito Kawamura 《Intermetallics》2002,10(11-12)
An original in situ ultrasonic echography technique was used to study the thermal stability and crystallisation of a Zr55Cu30Al10Ni5 bulk metallic glass between RT and 630 °C. Changes in Young's modulus with temperature were reported allowing to study the supercooled-liquid state and the crystallisation process. Investigations of viscoelastic properties gave information on the correlation factor (hierarchically correlated motion theory) and three distinct crystallisation stages were observed. Their kinetics were studied using Voigt's and Reuss' approximations for a two-phase material and comparisons with the Johnson–Mehl–Avrami–Kolmogorov theory allowed us to consider a mixed surface/internal nucleation for the first stage and a surface nucleation for the two last stages. 相似文献
19.
The effect that hydrostatic pressure has on the decomposition behavior in Cu54Ni6Zr22Ti18 bulk metallic glass (BMG) alloy was assessed using samples, which were isothermally annealed in the supercooled liquid region (SLR) with and without application of hydrostatic pressure. During subsequent annealing for the thermal analysis, the samples annealed under hydrostatic pressure displayed a slower crystallization process in the SLR, which is attributed to a retarded compositional decomposition of the BMG alloy under pressure. 相似文献
20.
Proper understanding of glass formation implies the knowledge of the thermodynamics of the undercooled melts. Specifically, high values of the excess specific heat of the liquid are expected for good glass-formers. Extending the work of Gillessen and Herlach [F. Gillessen, D.M. Herlach, J. Non-Cryst. Solids 117–118 (1990) 555–558], we re-propose a calculation of the temperature dependence of entropy difference between amorphous-liquid and crystal states.An amorphous Pd77.5Cu6Si16.5 alloy has been produced by injection casting in a cylindrical copper mould. DSC measurements in the liquid, amorphous and crystalline states were performed with samples sliced from the cylinder to determine the heat of fusion, of crystallization and the difference in specific heat capacity between amorphous-liquid and crystal phases. These thermodynamic quantities are used to calculate the thermodynamic functions of the liquid-glass with reference to the equilibrium crystal mixture. The data are compared to those of other bulk glass-formers in terms of fragility plots. 相似文献