Pd40Cu30Ni10P20 Bulk Metallic Glass Research Articles

Study of dynamical properties of Pd40Cu30Ni10P20 bulk metallic glass at various temperatures

Abstract In the present article, we study the dynamical properties such as velocity auto correlation function (VACF), power spectrum (PS) and mean square displacement (MSD) of Pd40Cu30N10P20 bulk metallic glass (BMG) computed using the local model potential approach at different temperatures i.e. 296 K, 573 K, 659 K 923 K, respectively. Such computations are performed with the static harmonic well approximation theory at various temperatures. The effective interatomic potential for aforementioned BMG is calculated using well established model pseudopotential of Jani et al. along with Farid et al. (F) local field correlation functions (LFCF) for studying the screening dependency on the aforesaid properties. It is observed that negative dip in the velocity auto correlation function decreases as the temperature increases and in results of the power spectrum, the peak is shifted towards lower ω observed as temperature increases. The obtained result of MSD concludes that the vibrating component in the atomic motion decreases as increases the temperatures. The velocity auto correlation function displays the transferability of the local pseudopotential in the present case of Pd-based BMG.

A biocompatible Pd-based BMG with excellent corrosive-wear resistance for implant applications

The mechanical properties, electrochemical behavior, wear and corrosive-wear performance of a Pd40Cu30Ni10P20 bulk metallic glass (BMG) were studied. It is found that the Pd-based BMG shows high hardness of over 500 HV, which is superior to that of conventional biomedical alloys, like the CoCrMo alloy, 316 L stainless steel (SS), and Ti6Al4V alloy. The Pd-based BMG possesses a great corrosion resistance in the phosphate buffer saline (PBS) solution, which is ascribed to the formation of a highly-protective Pd-enriched sub-surface structure. The Pd-based BMG exhibits the greater dry- and corrosive-wear resistance than that of traditional crystalline biomedical alloys studied in this work. This trend can effectively ensure the working longevity of the Pd-based BMG as orthopedic implant. The triobocorrosion experiment results illustrate that the extremely high corrosive-wear resistance of the Pd-based BMG can be attributed to the high passivation capacity during wet sliding. The possible mechanism of the corrosion-accelerating wear deterioration is discussed, which provides the guidance for the improvement in the corrosive-wear resistance of Pd-based BMGs for their potential biomedical applications.

Vibrational Dynamics of Pd39Ni10Cu30P21Bulk Metallic Glass

In the present study, we report the vibrational dynamics of Pd39Ni10Cu30P21 bulk metallic glass in terms of the phonon Eigen frequencies of the localized collective excitations using Show’s optimized model pseudopotential at room temperature. While theoretical effective atom model (EAM) with Wills-Harrison (WH) approach are used for the computation of the interatomic pair potential (PP) and pair correlation function (PCF). The phonon dispersion curves are computed through Hubbard-Beeby (HB) approach. Various elastic and thermodynamic properties have been reported from the elastic limit of the phonon dispersion curves. The screening dependency on the aforesaid properties is studied by adopting different kinds of local field correction functions

Experimental study on the surface characteristics of Pd-based bulk metallic glass

The metallic glass has many unique and desirable physical and chemical characteristics for their long-range disordered atomic structure, among them the interfacial properties of the metallic glasses are crucial for their applications and manufacturing. In this work, the contact wetting angles between the polymer melts and Pd40Cu30Ni10P20 bulk metallic glass (Pd-BMG) with four kinds of roughness were analyzed. Experiments show the order of four polymers wettability on Pd-BMG was PP>HDPE>COC>PC. The surface free energy of Pd-BMG was estimated by Owens–Wendt method using the contact angles of three testing liquids. Neumann method was also used to further evidence the surface free energy of Pd-BMG comparing with PTFE, mold steels NAK80 and LKM2343ESR. The results provide theoretical and technical supports for the fabrication of metallic glass micro mold and the parameter optimization of polymer micro injection molding.

Structural behaviour of Pd40Cu30Ni10P20 metallic glass under high pressure

The structural behaviour of Pd40Cu30Ni10P20 bulk metallic glass as a function of hydrostatic pressure up to 47.4 GPa was investigated by means of in situ high energy synchrotron X-ray diffraction patterns. Monotonic changes are observed in the diffraction data without any indication of a phase transition. In real space all maxima of the atomic pair correlation function including the nearest neighbour distance are decreasing and scale with pressure. The volume as function of hydrostatic pressure is extracted from the diffraction data. For the largest hydrostatic pressure of 47.4 GPa the volume is reduced by 18%. The bulk modulus B0 = 178 GPa was calculated from the diffraction data. The dependence of volume on pressure of Pd40Cu30Ni10P20 metallic glass can be well described by the Birch–Murnaghan equation of state.

Patterned superhydrophobic surface based on Pd-based metallic glass

Without any modification or post-treatment, superhydrophobic surfaces with good stability were fabricated by hot-embossing honeycomb patterns on Pd40Cu30Ni10P20 bulk metallic glass (BMG). The water contact angle reaches above 150° when the pitch between adjacent cells is larger than the critical size of 115.5 μm. The wetting behavior on the patterned BMG can be well rationalized in terms of the modified Cassie-Baxter theory [A. B. D. Cassie and S. Baxter, Trans. Faraday Soc. 40, 546 (1944)] by considering surface energy gradient. The achievement of the superhydrophobicity on BMG surface opens a window for the functional applications of metallic glasses.

Relaxation of the shear modulus of a metallic glass near the glass transition

Precise in situ measurements of the high-frequency (f≈560 kHz) shear modulus G of Pd40Cu30Ni10P20 bulk metallic glass at heating rates 0.38≤T·≤7.5 K/min have been performed. It has been found that structural relaxation leads to an increase of G below the glass transition temperature Tg while decreasing it at T>Tg. A quantitative analysis of this phenomenon within the framework of the interstitialcy theory has shown that structural relaxation below Tg can be understood as a decrease of the concentration of interstitialcy-like defects frozen-in upon glass production. The relaxation turns into defect multiplication on continued heating above Tg. The beginning of defect multiplication represents the glass transition temperature. An excellent agreement between calculated and experimental Tg ’s as a function of the heating rate has been found.

Isothermal kinetics and relaxation recovery of high-frequency shear modulus in the course of structural relaxation of Pd40Cu30Ni10P20 bulk glass

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.

The indentation size effect in Pd40Cu30Ni10P20 bulk metallic glass

The indentation size effect (ISE) in Pd40Cu30Ni10P20 bulk metallic glass was investigated through instrumented nanoindentation under different applied loads. It was found that both the indentation hardness and the reduced contact modulus decrease with an increase in the indentation depth. The ISE is more pronounced in the relaxed alloy than in the as-cast ones. Pop-in events and the subsurface shear band patterns underneath the nanoindenter are also observed to be sensitive to the depth of penetration. The ISE was discussed in terms of strain-induced softening and friction that is related to the ratio of the surface area to volume.

Anelastic deformation of a Pd40Cu30Ni10P20 bulk metallic glass during nanoindentation

Time-dependent deformation processes during nanoindentation have been investigated on a Pd40Cu30Ni10P20 bulk metallic glass. Deformation under constant load has been studied as a function of prior loading rate and temperature. The constant-load displacement of the indenter into the sample shows classic relaxation kinetics and reveals the importance of anelasticity for the mechanical behavior of metallic glasses at the nanoscale.

Plastic Deformation and Mechanical Softening of Pd40Cu30Ni10P20 Bulk Metallic Glass During Nanoindentation

Nanoindentation tests of Pd40Cu30Ni10P20 bulk metallic glass were performed over a wide range of indentation rates (from 0.04 up to 6.4 mN s−1) under the standard load control mode. New results using the feedback displacement control mode are also presented. The dependence of the pop-in formation on the loading rate is investigated. Variations in hardness and reduced elastic modulus as a function of the indentation rate are observed. A softening effect occurs when increasing the loading rate. This is explained by the differences in plastic deformation achieved at different indentation rates. The displacement control mode was used to avoid the shear localization of the free volume, leading to the almost complete absence of pop-ins along the loading curve. The obtained results suggest that plastic flow in bulk metallic glasses is governed by the rate of creation of free volume, which depends on the strain rate and its localization into shear bands.

Ageing behaviour of Pd40Cu30Ni10P20 bulk metallic glass during long-time isothermal annealing

In this paper, positron annihilation spectroscopy and differential scanning calorimetry were applied to study the structural relaxation of Pd40Cu30Ni10P20 bulk metallic glass during long-time annealing at 523 K. It was found that the relaxation of the alloy follows a two-stage process. In the initial stage, with increasing annealing time, the height of the glass transition peak (namely Δcp) increased, while the average positron lifetime decreased. The isothermal relaxation kinetics obeys a Kohlrausch law with exponent of β = 0.5± 0.03. However, when the annealing time is beyond 32 h, the height of the glass transition peak (Δcp) decreased, and the average positron lifetime increased. This is possibly due to the enhancement of the topological short-range ordering, which results in the generation of new defects on the interfaces between the solid-like regions and the liquid-like regions in amorphous phase. The experimental results were tentatively discussed in terms of free-volume theory and percolation theory.

Structural behavior of Pd40Cu30Ni10P20 bulk metallic glass below and above the glass transition

The thermal behavior of the structure of Pd40Cu30Ni10P20 bulk metallic glass has been investigated in situ through the glass transition by means of high-temperature x-ray synchrotron diffraction. The dependence of the x-ray structure factor S(q) of the Pd40Cu30Ni10P20 glass on temperature follows the Debye theory up to the glass transition with a Debye temperature θ=296 K. Above the glass transition temperature Tg, the temperature dependence of S(q) is altered, pointing to a continuous development of structural changes in the liquid with temperature. The atomic pair correlation functions g(r) indicate changes in short-range-order parameters of the first and the second neighborhood with temperature. The temperature dependence of structural parameters is different in glass and in supercooled liquid, with a continuous behavior through the glass transition. The nearest-neighbor distance decreases with temperature, changing the slope at Tg. The interatomic distances of higher coordination shells expand analogously to the macroscopic linear thermal expansion.

Structural Relaxation and Crystallization in a Pd40Cu30Ni10P20 Bulk Metallic Glass

ABSTRACTThe stability of a Pd40Cu30Ni10P20 bulk metallic glass (BMG) against structural relaxation is investigated by isothermal and isochronal annealing heat treatments below and above its glass transition temperature, Tg, for varying periods. Differential scanning calorimetry (DSC) of the annealed samples shows an excess endotherm at Tg, irrespective of the annealing temperature. This recovery peak evolves exponentially with annealing time and is due to the destruction of anneal-induced compositional short range ordering. The alloy exhibits a high resistance to crystallization on annealing below Tg and complex Pd- and Ni-phosphides evolve on annealing above Tg.

Pressure dependence of the elastic constants and vibrational anharmonicity ofPd39Ni10Cu30P21 bulk metallic glass

The pressure dependence of the acoustic velocities of a Pd39Ni10Cu30P21 bulkmetallic glass have been investigated up to 0.5 GPa at room temperature with thepulse echo overlap method. Two independent second-order elastic coefficientsC11 andC44and their pressure derivatives are yielded. The vibrational anharmonicity isshown by calculating both the acoustic mode Grüneisen parameters in thelong-wavelength limit and the thermal Grüneisen parameter, and this result iscompared with that for the Pd40Ni40P20 bulk glass.

Comparison of structural relaxation of Pd39Ni10Cu30P21 bulk metallic glass under ambient pressure and at a high pressure

Structural relaxations of a Pd39Ni10Cu30P21 bulk metallic glass (BMG) under ambient pressure and at a high pressure are compared by means of temperature-modulated differential scanning calorimetry (TMDSC) measurements. The structural relaxation is evaluated by the enthalpy recovery involved upon passing through the glass transition in the irreversible TMDSC curves. It is found that the isothermal relaxation of the BMG under ambient pressure leads to a lower-enthalpy state than that under a high pressure. The onset temperature for the enthalpy recovery process is found to exhibit a linear dependence on the recovery enthalpy.

Structural Relaxation of Pd39Ni10Cu30P21Bulk Metallic Glass Under High Pressure

The Pd39Ni10Cu30P21 bulk metallic glass isisothermally relaxed under various pressures. The degree of thestructural relaxation is evaluated in terms of the enthalpyrecovery behaviours involved in the irreversible glass transitionprocesses by using a temperature-modulated differential scanningcalorimetry technique. A roughly linear increase of the recoveryenthalpy is observed within the experimental pressure rangefrom 2.67 to 4.45 GPa, which reflects the release of the frozen-inenthalpy in the as-quenched glass with increasing relaxation pressure.The pressure dependence of the timescale of the enthalpy recoveryprocesses is also exhibited.

Pressure effects on irreversible and reversible contributions to the glass transition ofPd39Ni10Cu30P21bulk metallic glass

Pressure effect on the glass transition of a Pd39Ni10Cu30P21 bulk metallic glass is investigated by using a temperature-modulated differential scanning calorimetry technique. The pressure dependence of the irreversible and reversible components extracted from the total transition signal is revealed. It is found that the isothermal relaxation below the glass transition temperature under various pressures causes the changes of the irreversible and reversible thermodynamic properties. The time scales for the irreversible and reversible processes as well as their pressure dependence are obtained. The structural relaxation and the enthalpy recovery are discussed.

Elastic constants of Pd39Ni10Cu30P21 bulk metallic glass under high pressure

The pressure-dependent acoustic velocities of a Pd39Ni10Cu30P21 bulk metallic glass (BMG) have been measured up to 0.5 GPa by using an ultrasonic technique with the pulse echo overlap method. The elastic constants, the Debye temperature, and their pressure dependence are obtained. The isothermal equation of state (EOS) of the BMG is established in terms of the Murnaghan form. The atomic configurations of the BMG are discussed by comparing the elastic constants and the EOS with those of its metallic component and of other amorphous materials.

Ultrasonic investigation of Pd39Ni10Cu30P21 bulk metallic glass upon crystallization

Acoustic velocities of Pd39Ni10Cu30P21 bulk metallic glass (BMG) are measured by an ultrasonic technique upon annealing. The elastic constants and the Debye temperature are obtained. A large softening of the transverse phonon is exhibited in the as-quenched BMG relative to its crystallized state. Upon crystallization, the shear modulus and the Debye temperature increase by ∼30% and ∼12%, respectively; however, the density increases by only ∼0.6%. Some anomalous acoustic and elastic behaviors are observed near the glass transition temperature and in the supercooled liquid region of the BMG. The anomalies are explained with regard to the structural changes.