共查询到20条相似文献,搜索用时 15 毫秒
1.
Ductile bulk metallic glass 总被引:1,自引:0,他引:1
We report on experimental evidence of pronounced global plasticity measured in monolithic Pt57.5Cu14.7Ni5.3P22.5 bulk metallic glass under both bending and unconfined compression loading conditions. A plastic strain of 20% is measured, never before seen in metallic glasses. Also, permanent deformation and a strain exceeding 3% before failure is observed during bending of 4 mm thick samples. To date, no monolithic metallic material has exhibited such a combination of high strength, extensive ductility, and high elastic limit. The large plasticity is reflected in a high Poisson ratio of 0.42, which causes the tip of a shear band to extend rather than initiate a crack. This results in the formation of multiple shear bands and is the origin of the observed large global ductility and very high fracture toughness, approximately 80 MPa m(-1/2). 相似文献
2.
Pd80+x
Si20−x
(x = 0, 1, and 2) binary metallic glasses with the diameter ranging from 7 to 8 mm were prepared by a combination of fluxing
and water quenching or air cooling. Thermal analysis results show that with increasing Si content, the glass transition temperature
T
g, the initial crystallization temperature T
x and the onset crystallization temperature T
p of Pd-Si binary glassy alloys increase. Moreover, the supercooled liquid region reaches 61 K. It indicates that Pd-Si binary
alloys possess large glass forming ability, which can be greatly improved by fluxing treatment.
Supported by the National Basic Research Program of China (Grant No. 2007CB613905) and the National Natural Science Foundation
of China (Grant Nos. 50671050 and 50431030) 相似文献
3.
The evolution of the shear modulus and the damping decrement during irreversible structural relaxation in a bulk Pd40Cu30Ni10P20 metallic glass in a temperature range below the glass transition temperature has been studied with an inverse torsion pendulum at a frequency of ~25 Hz. It is shown that the irreversible relaxation can be recovered via quenching from temperatures above the glass transition temperature. The spectrum shape, the characteristic activation energies, and the attempt frequencies of the irreversible structural relaxation are estimated. 相似文献
4.
New class of plastic bulk metallic glass 总被引:1,自引:0,他引:1
Chen LY Fu ZD Zhang GQ Hao XP Jiang QK Wang XD Cao QP Franz H Liu YG Xie HS Zhang SL Wang BY Zeng YW Jiang JZ 《Physical review letters》2008,100(7):075501
An intrinsic plastic Cu(45)Zr(46)Al(7)Ti(2) bulk metallic glass (BMG) with high strength and superior compressive plastic strain of up to 32.5% was successfully fabricated by copper mold casting. The superior compressive plastic strain was attributed to a large amount of randomly distributed free volume induced by Ti minor alloying, which results in extensive shear band formation, branching, interaction and self-healing of minor cracks. The mechanism of plasticity presented here suggests that the creation of a large amount of free volume in BMGs by minor alloying or other methods might be a promising new way to enhance the plasticity of BMGs. 相似文献
5.
Das J Tang MB Kim KB Theissmann R Baier F Wang WH Eckert J 《Physical review letters》2005,94(20):205501
Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (< 1%) at room temperature. We present a new class of bulk metallic glass, which exhibits high strength of up to 2265 MPa together with extensive "work hardening" and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The "work-hardening" capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands. 相似文献
6.
A Zr-based bulk metallic glass (BMG) with a composition of (Zr75Cu25)78.5Ta4Ni10Al7.5 and a bulk metallic glass matrix composite (BMGC) with a composition of (Zr75Cu25)74.5Ta8Ni10Al7.5 have been prepared by copper-mold casting. The compressive deformation behavior of the BMG and BMGC was investigated in the
supercooled region at different temperatures and various strain rates ranging from 8×10−4 s−1 to 8×10−2 s−1. It was found that both the strain rate and test temperature significantly affect the deformation behavior of the two alloys.
The deformation follows Newtonian flow at low strain rates but non-Newtonian flow at high strain rates. The deformation mechanism
for the two kinds of alloys was discussed in terms of the transition state theory.
Supported by the National Natural Science Foundation of China (grant Nos. 50471060 and 50635020) 相似文献
7.
FAN ZhenJun ZHENG ZhiYuan & JIAO ZengBao School of Materials Sciences Technology China University of Geosciences Beijing China 《中国科学:物理学 力学 天文学(英文版)》2010,(5)
The compressive fracture characteristics of Zr-based bulk metallic glass under uniaxial compression tests are studied.The zigzag rheological behavior is observed in the compression stress-strain curves of amorphous alloys.At room temperature the uniaxial compression fracture takes place along the plane which is at a 45-degree angle to the direction of the compressive stress.The microstructure of a typical fracture pattern is the vein network.A unique,finger-like vein pattern is found to exist at the fractur... 相似文献
8.
By controlling the specimen aspect ratio and strain rate, compressive strains as high as 80% were obtained in an otherwise brittle metallic glass. Physical and mechanical properties were measured after deformation, and a systematic strain-induced softening was observed which contrasts sharply with the hardening typically observed in crystalline metals. If the deformed glass is treated as a composite of hard amorphous grains surrounded by soft shear-band boundaries, analogous to nanocrystalline materials that exhibit inverse Hall-Petch behavior, the correct functional form for the dependence of hardness on shear-band spacing is obtained. Deformation-induced softening leads naturally to shear localization and brittle fracture. 相似文献
9.
用铜模吸铸法获得了直径为5mm的一种新的Pr基大块非晶.与以往其他稀土-过渡金属(RE-TM)大块非晶不同的是,这种新的Pr基大块非晶具有明显的玻璃转变和稳定的过冷液相区,且其玻璃转变温度在目前已知的大块非晶中是最低的,Tg=409K.研究了该大块非晶的玻璃转变动力学,并给出了Kauzmann温度Tk、Vogel-Fulcher温度T0g及脆性参数m等重要参数.
关键词:
大块非晶
玻璃转变
脆性参数m 相似文献
10.
Fe-based bulk metallic glasses (BMGs) normally exhibit super high strength but significant brittleness at ambient temperature.
Therefore, it is difficult to investigate the plastic deformation behavior and mechanism in these alloys through conventional
tensile and compressive tests due to lack of distinct macroscopic plastic strain. In this work, the deformation behavior of
Fe52Cr15Mo9Er3C15B6 BMG was investigated through instrumented nanoindentation and uniaxial compressive tests. The results show that serrated
flow, the typical plastic deformation feature of BMGs, could not be found in as-cast and partially crystallized samples during
nanoindentation. In addition, the deformation behavior and mechanical properties of the alloy are insensitive to the applied
loading rate. The mechanism for the appearance of the peculiar deformation behavior in the Fe-based BMG is discussed in terms
of the temporal and spatial characteristics of shear banding during nanoindentation.
Supported by the National Natural Science Foundation of China (Grant Nos 50571109, 10572142 and 56771102) and the National
Basic Research Program of China (973 Program)(Grant No 2007CB613900) 相似文献
11.
The variations in the chemical compositions of the metallic glasses reported in the literature, as well as the overall lack of experimental data concerning the inhomogeneous deformation behaviour of metallic glass, make the evaluation of the effects of shear band/fracture behaviour on the mechanical properties of metallic glasses difficult. Isolating the effect of local shear band formation on bulk inhomogeneous flow would appear to be a first step in approaching this problem. The mechanical behaviour of Vitreloy metallic glass at room temperature and at various strain rates in tension and compression was investigated. The formation of multiple shear bands was observed at high strain rates. An increase in strain rate leads to enhanced ductility in tension and compression. Some aspects of the deformation processes in tension and compression are discussed. 相似文献
12.
The evolution of microstructure upon partial crystallization and its influence on the mechanical properties such as hardness, elastic modulus and viscosity in a La 55 Al 25 Cu 10 Ni 5 Co 5 bulk metallic glass alloy are studied. Specimens with various volume fractions of crystalline phases were obtained by annealing the as-cast amorphous alloy above its glass transition temperature and were characterized by transmission electron microscopy. Microscopic examination of the heat-treated samples shows short-range-ordered domains prior to nanocrystallization within the amorphous matrix, followed by the growth and impingement of the crystallites. Whereas the hardness of the annealed samples increases linearly with increasing crystallinity, the elastic modulus and the viscosity both increase abruptly when the crystalline volume fraction is about 40 vol.%, with a only minor variation on either side of this range. The sudden rises in the modulus and viscosity are similar to those in the literature data on the fracture strength of partially crystallized bulk amorphous alloys that shows a steep drop in strength at 30-50 vol.% crystallinity. On the basis of the microscopic observations, it is suggested that the interaction and formation of rigid networks of crystalline phases upon the attainment of a critical second-phase volume fraction may be the possible reason for the sudden change in mechanical properties. Percolation theory is utilized in further substantiating this hypothesis. 相似文献
13.
D. Ma A. D. Stoica X.-L. Wang Z. P. Lu T. Proffen 《Applied Physics A: Materials Science & Processing》2010,98(3):537-542
In this paper, we report the structure, optical, and gas-sensing properties of Co-doped ZnO nanocrystals prepared by a simple
solvothermal route. The red-shift of the band-gap edge is attributed to a merging of donor and conduction bands due to Co
doping. Photoluminescence (PL) spectra were used to study the dependence of doping on the deep-level emission, which show
obvious enhanced blue-green emission after Co doping. Gas sensors were prepared and tested for the detection of C2H5OH in air. It is found that the Co-doped nanocrystals have a significantly better sensing performance than pure ZnO, which
is comparable to the Au-functionalized ZnO sensors. We provide a possible explanation in terms of the sensing mechanism of
the surface reaction process. 相似文献
14.
《中国物理 B》2015,(6)
Dynamic strength behavior of Zr51Ti5Ni10Cu25Al9 bulk metallic glass(BMG) up to 66 GPa was investigated in a series of plate impact shock-release and shock-reload experiments.Particle velocity profiles measured at the sample/Li F window interface were used to estimate the shear stress,shear modulus,and yield stress in shocked BMG.Beyond confirming the previously reported strain-softening of shear stress during the shock loading process for BMGs,it is also shown that the softened Zr-BMG still has a high shear modulus and can support large yield stress when released or reloaded from the shocked state,and both the shear modulus and the yield stress appear as strain-hardening behaviors.The work provides a much clearer picture of the strength behavior of BMGs under shock loading,which is useful to comprehensively understand the plastic deformation mechanisms of BMGs. 相似文献
15.
Kazuki Komatsu Koji Munakata Kazuyuki Matsubayashi Yoshiya Uwatoko Yoshihiko Yokoyama Kazumasa Sugiyama 《高压研究》2015,35(3):254-262
Zirconium-based bulk metallic glass (Zr-based BMG) has outstanding properties as a cylinder material for piston-cylinder high pressure apparatuses and is especially useful for neutron scattering. The piston-cylinder consisting of a Zr-based BMG cylinder with outer/inner diameters of 8.8/2.5?mm sustains pressures up to 1.81?GPa and ruptured at 2.0?GPa, with pressure values determined by the superconducting temperature of lead. The neutron attenuation of Zr-based BMG is similar to that of TiZr null-scattering alloy and more transparent than that of CuBe alloy. No contamination of sharp Bragg reflections is observed in the neutron diffraction pattern for Zr-based BMG. The magnetic susceptibility of Zr-based BMG is similar to that of CuBe alloy; this leads to a potential application for measurements of magnetic properties under pressure. 相似文献
16.
17.
High speed impact experiments of rectangular plate-shaped Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG) were performed using a two-stage light gas gun. Under spherical shock waves with impact velocities ranging from 0.503 km/s to 4.917 km/s, obvious traces of laminated spallation at the back (free) surface and melting (liquid droplets) at the impact point were observed. The angles about 0?, 17?, 36?, and 90? to the shocking direction were shown in the internal samples because of the interaction between the compressive shock waves and the rarefaction waves. The compressive normal stress was found to induce the consequent temperature rise in the core of the shear band. 相似文献
18.
J. Du Q. Zheng E. Brück K.H.J. Buschow W.J. Feng Z.D. Zhang 《Journal of magnetism and magnetic materials》2009,321(5):413-417
A noncollinear-ferromagnetic spin-glass-like state was observed in Tb55Co20Al25 bulk metallic glass due to the strong random magnetic anisotropy. Associated with this behavior, we observed a comparatively large magnetic entropy change (ΔSm is 9.75 J K−1 kg−1) in a field change of 7 T and a correspondingly high value of the magnetic refrigeration capacity (RC is 540 J kg−1) with almost no hysteresis loss in the vicinity of the so-called Curie temperature. This opens the possibility of using this material for magnetic cooling purposes. 相似文献
19.
Atomic diffusion in deformed Pd(40)Ni(40)P(20) bulk metallic glass containing a single family of deformation-induced shear bands was measured by the radiotracer technique. The significant, by orders of magnitude, enhancement of the diffusion rate with respect to that in the untransformed matrix suggests that the shear bands represent short-circuit diffusion paths. Correlations between diffusivity, viscosity, and the excess free volume distribution inside of shear bands are discussed. 相似文献
20.
Samples of Zr(46.25)Ti(8.25)Cu(7.5)Ni(10)Be(27.5) were isothermally annealed and quenched near the glass transition temperature and studied by the pulse-echo overlap technique. The shear modulus G of the samples shows a strong reversible dependence on annealing temperatures and, thus, on the specific configurational potential energy of the equilibrium liquid. The low-T dependence of G of the configurationally frozen glasses shows linear temperature dependence as expected by Debye-Grüneisen theory. The T dependence of G in the liquid state is directly related to the viscosity and fragility of the liquid. 相似文献