Bulk Glassy Alloys Research Articles

Unusual solidification behavior of a Zr–Cu–Ni–Al bulk glassy alloy made from low-purity Zr

This paper reports on the unusual solidification behavior of Zr 55Cu 30Al 10Ni 5 bulk glassy alloy produced using low-purity Zr in which both primary and eutectic-type structural constituents were formed simultaneously during solidification of the melt. Additionally, two different types of primary crystalline phases were observed. One of them was cF96 and contained all the four constituent elements. Reasons for these observations have been related to the presence of impurities in the alloy leading to inhomogeneous nucleation and consequent modification of the crystallization behavior. The structure and thermal stability of the samples were studied using X-ray diffraction, scanning and transmission electron microscopy, as well as differential scanning calorimetry methods. Although the cast alloys made with low-purity Zr showed somewhat decreased glass-forming ability, their mechanical strength was still high.

Phase structure and crystallization of the bulk glassy FeCoZrWB alloys

AbstractIn the present work, the high‐energy X‐ray diffraction (XRD) measurements performed using monochromatic synchrotron radiation of 112 keV (λ=0.110696 Å), were utilized to compare a phase constitution of melt‐spun ribbon and suction‐cast rods of Fe61Co10+xZr5W4–xB20 alloys (where x = 0, 2, 3 at.%). For bulk amorphous samples of the investigated alloys DSC studies allowed to determine the activation energies of crystal growth and differences in crystallization kinetics at constant heating rates. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Formation and mechanical properties of Zr–Ni–Al glassy alloys with high glass-forming ability

The addition of Al to a binary Zr 75Ni 25 alloy greatly increases the stabilization of the supercooled liquid as well as the glass-forming ability (GFA) in Zr 75− x Ni 25Al x ( x = 0–24) alloy series. The large supercooled liquid region (Δ T x ) of over 80 K and critical sample diameter ( d c) for glass formation above 12 mm were obtained in a wide composition range of x = 11–19. The largest d c of 15 mm was fabricated for an off-eutectic Zr 60Ni 25Al 15 alloy, which has the largest Δ T x of 93 K and γ value of 0.396. The bulk glassy alloys exhibited excellent mechanical properties, i.e., high compressive fracture strength of 1662–1958 MPa and large compressive plastic strain of 3.0–4.7%.

Effects of B and Si contents on glass-forming ability and soft-magnetic properties in (Co0.89Fe0.057Nb0.053)100−x(B0.8Si0.2)x glassy alloys

The effects of B and Si contents on the glass-forming ability (GFA) and soft-magnetic properties of (Co0.89Fe0.057Nb0.053)100−x(B0.8Si0.2)x (x=22–30) alloys were investigated. The thermal stability of the supercooled liquid increased with increasing the B and Si contents from x=24 to 28, and accompanying the decreases of liquidus temperature of alloys. As a result, The (Co0.89Fe0.057Nb0.053)100−x(B0.8Si0.2)x bulk glassy alloys with diameters up to 3.5 mm were synthesized in the composition range of x=24–28. In addition to high GFA, the Co-based glassy alloys exhibit excellent soft-magnetic properties as well, i.e., moderate saturation magnetization of 0.51–0.72 T, low coercive force of 0.4–1.5 A/m, and high initial permeability of 22 340–29 570 at 1 kHz under a field of 1 A/m.

Enhanced glass-forming ability of FeCoBSiNb bulk glassy alloys prepared using commercial raw materials through the optimization of Nb content

We optimized the alloy compositions by modifying the Nb content in [(Fe0.5Co0.5)0.75B0.20Si0.05]100−xNbx(x=3.6–4.4) alloy system. As a result, it was found that the Nb content of 4.3 at. % was effective for approaching alloy to a eutectic point. By copper mold casting, [(Fe0.5Co0.5)0.75B0.20Si0.05]95.7Nb4.3 bulk glassy alloy rods with diameters up to 4 mm were successfully synthesized even using commercial raw materials. These glassy alloys exhibit a rather high saturation magnetization of 0.77 T and low coercive force of 2.5 A/m.

Free volume in Zr-based bulk glassy alloys studied by positron annihilation techniques

The eutectic Zr50Cu40Al10 bulk glassy (BG) alloys, which have a good glass forming ability, have been investigated for various properties, such as toughness, electronic resistivity and so on. Recently, the hypoeutectic Zr60Cu30Al10 BG alloys have been paid attention, because they exhibit no degradation of ductility and toughness after the isothermal annealing below the glass transition temperature (Tg). Although the toughness correlates with the free volume to be considered, the free volume of the hypoeutectic BG alloy has not been assessed in detail so far. In order to study the free volume in each BG alloy, therefore, positron annihilation lifetime and coincidence Doppler broadening (CDB) measurements have been performed for Zr60Cu30Al10 (hypoeutectic) and Zr55Cu35Al10 (middle-composition) and Zr50Cu40Al10 (eutectic) BG alloys. The value of the positron lifetime for hypoeutectic BG alloy is virtually the same. Additionally, the CDB ratio curve for hypoeutectic alloy dose not match that for eutectic alloy in an electron momentum region around 0.015 m0c, indicating that the fraction of Zr atoms around the free volume in hypoeutectic BG alloy is greater than that in eutectic BG alloy. Moreover, the CDB results show that the local structure around free volume for hypoeutectic BG alloy is different from that for eutectic BG alloy.

Enhancement of glass-forming ability of CoFeBSiNb bulk glassy alloys with excellent soft-magnetic properties and superhigh strength

Co-based bulk glassy alloys with diameters up to 4.5 mm were formed in Co 46Fe 20B 22+ x Si 6− x Nb 6 ( x = 0–2) system. The increase of B to Si concentration ratio is effective in improving the glass-forming ability. In addition to high glass-forming ability, the glassy alloys exhibit excellent soft-magnetic properties, i.e., high saturation magnetization of 0.63–0.69 T, low coercive force of 1.17–2.35 A/m, and high effective permeability of 1.36–2.65 × 10 4 at 1 kHz under a field of 1 A/m. The bulk glassy alloys also exhibit superhigh fracture strength of 4400 MPa.

A Ti-based bulk glassy alloy with high strength and good glass forming ability

Ti-based bulk metallic glasses have attracted lots of attention of scientific researchers due to their lightweight, low cost and high specific strength. But only a few Ti-based alloys have been reported possessing large glass forming ability. Then, research on new Ti-based alloys with good glass forming ability is necessary and important. In present work, rods of Ti 43.15Zr 9.59Cu 36.24Ni 9.06Sn 1.96 glassy alloy with diameter of 3 mm have been fabricated by using copper mould casting method. It has been found that this Ti-based bulk metallic glass possesses good mechanical properties at room temperature. The compressive yield strength and the fracture strength of the glassy alloy are 2360 MPa and 2640 MPa, respectively, together with the plastic strain of 2.24%. The present results show that adding an element or increasing the amount of an element with large difference in atomic size ratio with other main constitutive elements and more negative mixing heat with other main constitutive elements in an alloy would benefit to enhance the glass forming ability of the alloy.

Corrosion resistance and XPS studies of Ni-rich Ni–Pd–P–B bulk glassy alloys

New Ni-rich Ni–Pd–P–B bulk glassy alloys with high glass-forming ability were formed by water quenching. The Ni 60Pd 20P 17B 3 and Ni 65Pd 15P 17B 3 alloys possess high corrosion resistance in 1N H 2SO 4 and 3 mass% NaCl solutions. In both solutions, their corrosion resistance decreases with increasing Ni content in the alloys. The origin of high corrosion resistance for the Ni 60Pd 20P 17B 3 alloy in the corrosive solutions is explained by formation of the Pd-enriched sub-surface layer, which is able to protect the alloy against the corrosion.

Effect of Nb addition on the glass-forming ability, mechanical and soft-magnetic properties in (Co 0.942Fe 0.058) 72− xNb xB 22.4Si 5.6 bulk glassy alloys

The effect of Nb addition on the glass-forming ability (GFA), mechanical and soft-magnetic properties in (Co 0.942Fe 0.058) 72− x Nb x B 22.4Si 5.6 alloys system was investigated. In addition to the increase of glass-forming ability, the increase of Nb content was found to be effective for the improvement of mechanical and soft-magnetic properties. By copper mold casting, Co-based bulk glassy alloys with diameters up to 4 mm were formed in (Co 0.942Fe 0.058) 67Nb 5B 22.4Si 5.6 glassy alloy. The bulk glassy alloys exhibit a superhigh fracture strength of 2980–3600 MPa and Young's modulus of 121–166 GPa. The bulk glassy alloys also exhibit excellent soft-magnetic properties, i.e., high saturation magnetization of 0.6 T, low coercive force within 0.2–0.5 A/m, high permeability of 47165 at 1 KHz and zero magnetostriction.

Glass-forming ability and magnetic properties of CoFeMoYB bulk glassy alloys with large supercooled liquid region

Co-based bulk glassy alloys with diameters up to 4 mm were formed in Co 41+ x Fe 28Mo 4Y 5− x B 22 ( x = 0–1.5) system. The effect of Y content on the glass-forming ability and soft-magnetic properties of the Co-based bulk glassy alloys was investigated. With an increase of Y content from 3.5 to 5 at%, in addition to slight increases of glass transition temperature from 843 to 847 K and supercooled liquid region increases from 73 to 94 K, the addition of Y was found to be effective in approaching alloy to a eutectic point. Except for high glass-forming ability, the Co-based bulk glassy alloys exhibit good soft-magnetic properties, i.e., high saturation magnetization of 0.80–0.87 T, low coercive force of 2.87–3.34 A/m, high effective permeability at 1 kHz of 1.26–1.74 × 10 4 under a field of 1 A/m.

Preparation of (Ti 0.45Cu 0.378Zr 0.10Ni 0.072) 100− xSn x bulk metallic glasses

The quinary alloys of Ti–Cu–Zr–Ni–Sn, (Ti 0.45Cu 0.378Zr 0.10Ni 0.072) 100− x Sn x ( x = 0, 2, 4, 6, and 8 at.%), have been prepared and studied. The (Ti 0.45Cu 0.378Zr 0.10Ni 0.072) 100− x Sn x ( x = 0, 2, 4, 6) bulk glassy rods can been prepared by copper-mold casting. Among these glassy alloys, the (Ti 0.45Cu 0.378Zr 0.10Ni 0.072) 98Sn 2 shows better glass-forming ability than others. Thermal analysis results show that the supercooled liquid range of the Ti–Cu–Zr–Ni glassy alloy has been increased with the addition of Sn. In addition, the as-prepared (Ti 0.45Cu 0.378Zr 0.10Ni 0.072) 98Sn 2 glassy alloy exhibits yield strength and fracture strength of 2260 and 2650 MPa, respectively, together with a compressive plastic strain of 7.6%. The results show that the quinary Ti–Cu–Zr–Ni–Sn bulk glassy alloy possesses good mechanical properties.

Effects of cooling rates on the mechanical properties of a Ti-based bulk metallic glass

Mechanical properties of the glassy specimens fabricated at different cooling rates with a composition of Ti40Zr25Cu12Ni3Be20 were systematically investigated. It was confirmed that faster cooling rates caused not only a larger amount of frozen-in free volume but also a higher glass transition temperature in the bulk glassy alloy. Increase in the free volume was found to favor plastic deformation and then to give rise to larger compressive plasticity, whilst the rise in the glass transition temperature seemed to be closely related to the higher yield strength. Moreover, the increase of yield strength and plasticity induced by fast cooling rates may also be associated with the residual stress generated during the fabrication process. Our results suggest that the deformation behavior of bulk metallic glasses is sensitive to various factors and influences from the other factors should be excluded as far as cooling-rate effects on bulk metallic glasses are considered.

Formation of Ca–P layer on the Ti-based bulk glassy alloy by chemical treatment

In the present paper, a chemical treatment method has been employed to prepare a bioactive layer on the surface of Ti 40Zr 10Cu 34Pd 14Sn 2 bulk glassy alloy. Prior to forming an apatite layer, all samples were dipped in mixed acid (HNO 3 and HF) aqueous solution and boiled in 1.2 M NaOH aqueous solution. Then, they were soaked in simulated body fluid (SBF) to form an apatite layer on the surface. The apatite layer was characterized by X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS) and environment scanning electron microscopy (ESEM). The results show: a dense and uniform calcium phosphate layer mainly composed of HA and Ca 2P 2O 7 was rapidly deposited on the pre-calcified Ti 40Zr 10Cu 34Pd 14Sn 2 bulk glassy alloy in SBF within 7 days.

Thermal and Magnetic Properties in (FeBSi)NbY Bulk Glassy Alloys

The thermal and magnetic properties of (Fe75B20Si5)93Nb4Y3 and (Fe78B14Si8)93Nb4Y3 metallic glasses, in cylinder and ribbon form, have been studied and compared. Bulk samples were prepared by water-cooled Cu-mold casting technique. Ribbons having the same compositions have been prepared by rapid quenching. Selected samples have been submitted to furnace annealing to study the crystallization behavior and the corresponding structure has been studied by X-ray diffraction technique. Room-temperature hysteresis loops and magnetisation behavior as a function of temperature have been measured by a Vibrating Sample Magnetometer (VSM). In this paper, the effect of small addition in the rapidly solidified ternary system Fe78B14Si8 either on the glass formation or the magnetic properties will be shown.

Enhancement of plastic deformability in Fe–Ni–Nb–B bulk glassy alloys by controlling the Ni-to-Fe concentration ratio

The influence of partial replacement of Fe by Ni in (Fe1−xNix)71Nb6B23 (0≤x≤0.5) bulk glassy alloys on the enhancement of the plasticity has been investigated. The increase of the Ni-to-Fe concentration ratio effectively improves the compressive plasticity. The (Fe0.5Ni0.5)71Nb6B23 alloy exhibits an enhanced plastic strain of ∼4.2%, together with high strength and distinct strain hardeninglike characteristics, when compared with the Ni-free Fe71Nb6B23 glass. The improved mechanical properties are ascribed to the control of the intrinsic elastic properties, followed by favorably tuning the interatomic interaction.

Microstructure and mechanical properties of crystalline particulates dispersed Ni-based metallic glassy composites fabricated by spark plasma sintering

Using the mixed powders of the gas-atomized Ni-based metallic glassy alloy powder blended with metal W or ceramic SiC particulates, we fabricated large-size bulk glassy alloy composites (GACs) by a spark plasma sintering (SPS) process. The microstructure and mechanical properties of the prepared GAC specimens were investigated, and the effect of addition amount of the crystalline particulates on the properties of the sintered GAC specimens was discussed. The Ni-based bulk GACs with ultrahigh strength and enhanced plasticity were produced. The improvement of plasticity of the fabricated bulk GACs is attributed to the structural inhomogeneity caused by the addition particulates inclusion. The optimum content of the crystalline particulates is about 5–10 vol.%.

Synthesis and Mechanical Properties of New Cu-Based Cu-Zr-Al Glassy Alloys with Critical Diameters up to Centimeter Order

A new Cu-based Cu-Zr-Al glassy alloy has been found to exhibit very high glass-forming ability, wide supercooled liquid region and high fracture strength. The addition of Al to a binary eutectic Cu55Zr45 alloy significantly increases the stabilization of supercooled liquid as well as glass-forming ability in Cu55 xZr45Alx (x 1⁄4 0 to 10) alloy series. The largest supercooled liquid region of 80K, reduced glass transition temperature of 0.60 and value of 0.417 are simultaneously obtained for a ternary eutectic Cu47Zr45Al8 alloy, which can fabricate fully glassy sample with critical diameters up to 15mm by copper mold casting. The bulk glassy alloy also exhibits high compressive fracture strength of over 1900MPa and the high Young’s modulus above 100GPa. [doi:10.2320/matertrans.MBW200928]

Formation, Structure, and Crystallization Behavior of Cu-Based Bulk Glass-Forming Alloys

We studied Cu-Zr–based alloys having exceptionally high glass-forming ability (GFA) and investigated the influence of Ag and Al addition on their structure and crystallization behavior. Most of the bulk glassy alloys (BGAs) do not contain any crystals, while some samples studied by high-resolution transmission electron microscopy (HRTEM) were found to contain well-developed medium-range order zones and nanoparticles in a bulk form. The crystallization kinetics of Cu55Zr45, Cu50Zr50, Cu55–xZr45Agx (x = 0, 10, 20), Cu45Zr45Al5Ag5, Cu44Ag15Zr36Ti5, and Cu36Zr48Al8Ag8 glassy alloys was analyzed. An influence of the cooling rate on the formation of glassy phase and thermal stability of the Cu-based glassy alloys on heating was also studied. The crystallization kinetics and phase composition of the ribbon-shape and bulk glassy samples of Cu36Zr48Al8Ag8 alloys were also analyzed. The results also indicate that the best glass-forming compositions are possibly located at slightly off-eutectic area, owing to the shift of the eutectic point due to the nonequilibrium processing conditions.

Effect of germanium addition on the physical properties of Se–Te glassy semiconductors

The effect of germanium addition on the physical properties, i.e. density, molar volume, compactness, number of lone-pair electrons, average coordination number, heat of atomization, mean bond energy, cohesive energy and glass-transition temperature, of (Se80Te20)100− x Ge x (x = 0, 2, 4, 6) bulk glassy alloys was investigated. The density of the glassy alloys is found to decrease with increasing Ge content. The molar volume and compactness of the structure of the glass were determined from the measured density. The mean bond energy is proportional to the glass-transition temperature. The cohesive energy of the samples has been calculated using a chemical bond approach and is correlated with an increase in the optical energy gap with increase in the Ge content. The heat of atomization was also calculated and correlated with the optical energy gap. The glass-transition temperature has been estimated using different methods and is found to increase with an increase of Ge content.