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1.
Isochronous relaxation of tensile stresses is measured in a bulk Pd40Cu30Ni10P20 metallic glass in the initial state and after certain thermal treatments. The results of measurements are used to find the energy spectrum of irreversible structural relaxation, from which the temperature dependence of shear viscosity is then calculated. This dependence is also found independently from measurements of creep in the same glass. The calculated viscosity is shown to agree well with the experimental data.  相似文献   

2.
Isothermal kinetics of relaxation of the high-frequency (1.4 MHz) shear modulus during structural relaxation of Pd40Cu30Ni10P20 bulk metallic glass below the glass transition temperature is studied by an in situ method of contactless electromagnetic acoustic transformation. The kinetic law of relaxation is established. It is shown that quenching of aged samples from the supercooled liquid state leads to a decrease in the absolute value of shear modulus to below the initial value; the degree of subsequent isothermal relaxation of the modulus may be several times higher than the initial value. Possible reasons for relaxation and recovery of the shear modulus are considered.  相似文献   

3.
The structural relaxation of a bulk Pd40Cu30Ni10P20 metallic glass is studied by measuring the electrical resistivity and infralow-frequency (0.05 Hz) internal friction. It is demonstrated that the structural relaxation in thermally aged samples can be restored by quenching them from a supercooled liquid state. It is found that the degree of relaxation after quenching can exceed the initial one by several times.  相似文献   

4.
The phase transitions in Pd40Ni10Cu30P20 bulk metallic glass (BMG) have been studied under high pressure and high temperature (HP & HT) by X-ray diffaction measurements with synchrotron radiation source. We found that the BMG underwent a phase transitions of amorphous-crystalline-amorphous at 10 GPa upon heating. The parallel experiments were carried out at 7 GPa, while we did not observe the amorphous-crystalline-amorphous transitions by increasing temperature. Quenching the melted BMG at 7 GPa, it was found that the phase crystallized from the melt differed from the primary phase crystallized from the starting amorphous solid upon heating suggesting there existed a distinct mechanism in two cases.  相似文献   

5.
The electrical resistances of ribbon and bulk Pd40Cu30Ni10P20 metallic glasses, whose quenching rates differ by four orders of magnitude, were precisely measured during cyclic heating. Three stages of electrical resistance relaxation are detected as the maximum heating temperature increases. The first and third stages decrease the electrical resistance, and the second stage increases it. The first stage is shown to be caused by the relaxation of deformation-induced internal stresses and not to be related to the excess free volume concentration, which differs by a factor of about 2 in the ribbon and bulk samples. The second stage reflects structural relaxation in the glass and is only partly related to its free volume. The third relaxation stage is assumed to be caused by fine precrystallization phenomena like phase separation. The effect of deformation by rolling or quenching from the temperature range of a supercooled melt on the resistance relaxation kinetics was also studied.  相似文献   

6.
The effect of heat treatment over the range from room temperature to 500°C on the elastic properties of a bulk amorphous Pd40Cu30Ni10P20 alloy was studied. It is shown that the increase in the shear modulus under crystallization of the alloy is two-staged and that the most significant increase in the modulus occurs at the second stage. The obtained results are compared to the x-ray structural data. It is also found that the density characteristics of the as-cast material change very slightly during the transformation from the amorphous to the crystal state, with the density decreasing slightly due to crystallization.  相似文献   

7.
Ti42.5Zr7.5Cu40Ni5Sn5 bulk metallic glass with a critical diameter of 4 mm was fabricated by the conventional copper mould casting method. The supercooled liquid region ΔT x, reduced glass transition temperature T rg, γ parameter, and δ parameter of the alloy were measured to be 63.9 K, 0.561, 0.393, and 1.400, respectively, implying that the alloy has an excellent glass-forming ability. The bulk metallic glass exhibits high compressive fracture strength of 2162 MPa with distinct plastic strain of 0.9%. The fracture surface consists mainly of vein-like patterns, typical of bulk glassy alloys. Supported by the Program for New Century Excellent Talents in University of China and the National Natural Science Foundation of China (NSFC)(Grant No. 50771040)  相似文献   

8.
The laws of atomic restructuring in the Cu80Zr20 metallic glass during melt quenching are studied by molecular dynamics simulation using statistical-geometrical analysis based on Voronoi polyhedra and cluster analysis. The morphology and size distribution of polyhedral nanoclusters in the glass structure are investigated.  相似文献   

9.
Depth-sensing (indentation) testing is used to study the characteristics of a serrated plastic flow in a Pd40Cu30Ni10P20 bulk amorphous alloy, and the boundaries between the regions of serrated and homogeneous plastic deformation are determined.  相似文献   

10.
Dispersion of collective modes in metallic glass (Zr40Be60, composed of disparate mass particles) was measured at small-angle spectrometer BRISP at the ILL what enabled us to extend to lower momentum transfers unlike to high-angle spectrometer IN4 at the ILL. It was shown that the behavior of the optical mode in the metallic glass is similar to the behavior of optic modes in the other systems with non-sized atoms (liquid LiPb, inert gas mixtures with high density (He65Ne35)).  相似文献   

11.
The effect of elastic loading on the velocity of propagation of acoustic waves in a solid is calculated (to the second order in the applied load). The results of the calculations and the experimental data on the effect of uniaxial loading on the propagation of ultrasonic waves in the bulk metallic glass Zr52.5Ti5Cu17.9Ni14.6Al10 are used to estimate the third-order and fourth-order elastic moduli.  相似文献   

12.
Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG) is annealed at 573 K under 3 GPa and its structural relaxation is investigated by X-ray diffraction, ultrasonic study, compression as well as sliding wear measurements. It is found that after the ZrTiCuNiBe BMG sample was annealed under high pressure, the mechanical properties were improved. Moreover, theBMG with relaxed structure exhibits markedly different acoustic properties. These results are attributed to the fact that relaxation under high-pressure results in a microstructural transformation in the BMG.  相似文献   

13.
The compression of a Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG) is investigated at room temperature up to 24 GPa using in-situ high pressure energy dispersive X-ray diffraction with a synchrotron radiation source. The pressure-induced structural relaxation is exhibited. It is found that below about 8 GPa, the existence of excess free volume contributes to the rapid structural relaxation, which gives rise to the rapid volumetric change, and the structural relaxation results in the structural stiffness under higher pressure.  相似文献   

14.
The effect of severe plastic deformation by torsion under Bridgman anvil pressure (SPDT) on the electrical, magnetic, and optical properties of the Cu60Pd40 alloy was studied. It is shown that, after the alloy is disordered, the Curie-Weiss constants of the paramagnetic component are changed insignificantly. In this case, the temperature-independent negative component of the magnetic susceptibility decreases more than fivefold. The electrical resistance and negative thermopower, on the contrary, increase severalfold as a result of SPDT. The character of the optical conductivity is discussed using the band structure calculation results.  相似文献   

15.
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   

16.
17.
The effect of atomic disordering and alloying with d elements (Fe, Pd, Cu) on the transport and magnetic properties of Cu3Pd alloys has been investigated at low temperatures (T < 80 K) in strong magnetic fields (H ≤ 8 MA/m). The specific features of the crystal structure and temperature and field dependences of the electrical resistance, magnetoresistance, Hall effect, and magnetic susceptibility of Cu72Pd28, Cu75Pd25, Cu80Pd20 and Cu74.5Pd24.5Fe1 alloys are discussed.  相似文献   

18.
It has been established that quenching from the supercooled liquid state of the aged metallic glass Pd40Cu30Ni10P20 causes the recovery of its deformability, which manifests itself in measurements of the torque relaxation under conditions of isochronous heating.  相似文献   

19.
The influence of plastic deformation on the structure of the Pd40Ni40P20 amorphous alloy has been investigated using X-ray diffraction and measurements of the velocity of sound. It has been revealed that the rolling of the sample leads to a change in the structure of the amorphous phase (distortion of the first coordination sphere) and that the structural transformations are more pronounced in the near-surface region of the sample. The rolling also results in a decrease in the transverse velocity of sound. The observed effects decrease with time. It has been demonstrated that the revealed effects are associated with the inelastic deformation of the amorphous alloy.  相似文献   

20.
In this study, the temperature effects on the structural evolution of theZr70Pd30 binary alloy in the glassy and liquid states werestudied using the molecular dynamics simulations based on the many-body type tight-bindingpotential. We considered the following properties in detail: the temperature dependence ofthe volume, the partial and total pair distribution functions and the simulated glasstransition temperature. The effects of the cooling rates on the glass transitiontemperature were examined. The Wendt-Abraham parameter was calculated to determine theglass transition temperature of Zr70Pd30 glassy alloy. The pair analysis technique ofHoneycutt-Andersen was applied to define local atomic arrangements produced from moleculardynamics simulations. The results show that the icosahedral ordering in glassy state hasbeen composed during quenching period, and the simulated glass transition temperature andthe total pair distribution functions are in good agreement with the experimental data.  相似文献   

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