Bulk Metallic Glassy Alloy Research Articles

Synthesizing of Novel Bulk (Zr67Cu33)100−xWx(x; 5–30 at%) Glassy Alloys by Spark Plasma Sintering of Mechanically Alloyed Powders

Metallic glassy alloys with their short-range order have received considerable attention since their discovery in 1960’s. The worldwide interest in metallic glassy alloys is attributed to their unique mechanical, physical, and chemical properties, which cannot be found together in long-range order alloys of the same compositions. Traditional preparation methods of metallic glasses, such as rapid solidification of melts, always restrict the formation of glassy alloys with large atomic fraction (above 3–5 at%) of high melting point metals (Ta, Mo, W). In this study, (Zr67Cu33)100−xWx(x; 5–30 at%) metallic glassy alloys were fabricated through a mechanical alloying approach, which starts from the elemental powders. This system shows excellent glass forming ability in a wide range of W (0 ≤ x ≥ 30 at%). We have proposed a spark plasma sintering technique to prepare nearly full-dense large sized (20 × 20 mm) bulk metallic glassy alloys. The as-consolidated bulk metallic glassy alloys were seen to possess high thermal stability when compared with the other metallic glassy systems. This is implied by their high glass transition temperature (722–735 K), wide range of supercooled liquid region (39 K to over 100 K), and high values of crystallization temperature (761 K to 823 K). In addition, the fabricated ternary systems have revealed high microhardness values.

Fatigue properties of a nanocrystalline titanium based bulk metallic glassy alloy

Abstract To obtain a better understanding of the fatigue properties and crack growth characteristics of a nanocrystalline titanium based bulk metal glasses (Ti-BMG) made by vacuumed casting process, the fatigue failure mechanisms of Ti-BMG have been investigated via S – N and da/dN – ΔK tests. For comparison, the crystalline Ti alloy Ti-Al6V4 was also employed. The fatigue strength in the early fatigue stage was high for Ti-BMG due to the high tensile strength. However, the fatigue strength decreased significantly in the late fatigue stage. The higher slope of S – N relation was detected for Ti-BMG, which crossed that for the Ti-Al6V4 sample around 5 × 103 cycles. In the higher Region II, the fatigue crack growth rate was of similar level for both Ti-BMG and Ti-Al6V4 due to their similar strain energy. In the lower Region II, however, the lower crack growth resistance was obtained for Ti-BMG, as compared to Ti-Al6V4. This was attributed to the high crack driving force for Ti-BMG, caused by the weak roughness-induced crack closure. Such crack closing characteristics of Ti-BMG were systematically investigated by various experimental techniques.

On the shear band velocity in metallic glasses: A high-speed imaging study

Development of localised shear bands (SB) in bulk metallic glassy (BMG) alloys was investigated by a high-speed microscopic imaging technique. The velocities of SBs propagating by a progressive mechanism were found to be in the m/s range. It has been shown that after rapid initiation, the mean SB velocity decays as a function of time t, exhibiting a scaling-like t−n behaviour with n close to 2 over several orders of magnitude.

Fabrication of new metallic glassy Ti40.6Cu15.4Ni8.5Al5.5W30 alloy powders by mechanical alloying and subsequent SPS consolidation

Mechanical alloying approach, using a low-energy ball milling technique was employed for synthesizing metallic glassy Ti40.6Cu15.4Ni8.5Al5.5W30 alloy powders. The powders of the product obtained after 200h of milling possessed high thermal stability, characterized by a wide supercooled liquid region of 90K and crystallization temperature began at 827K. The powders were successfully consolidated into full dense bulk metallic glass at temperature laid above its glass transition temperature, using spark plasma sintering technique. The as-consolidated bulk metallic glassy alloy possessed extraordinary mechanical properties, such as high values of microhardness (∼11.61GPa). Moreover, the measured friction coefficient of this new bulk metallic glassy alloy was 0.32.

Cladding of Mg alloy with Zr based BMG Alloy

In the present work, an attempt has been made to clad AZ31 magnesium alloy with Zr-based bulk metallic glassy alloy (Vit-1), by casting method. The interface studies conducted using SEM-EDS line scan indicate that a good bond is formed at the clad interface of Zr and Mg. And the mechanism involved is discussed herein.

Development of FeNiNbSiBP bulk metallic glassy alloys with excellent magnetic properties and high glass forming ability evaluated by different criterions

Fe38Ni38Nb2.5B21.5−x−yPxSiy (x, y = 1–8) bulk metallic glassy alloys with high glass forming ability and excellent magnetic properties were developed. Bulk samples with maximum diameters of 3 mm are fabricated by copper mold casting method. The glassy alloys have large ΔTx of 40–70 K. The alloys exhibit excellent magnetic properties like extremely low Hc of 0.5–0.8 A/m, high μe of 1.6–2.85 × 104 and comparatively high Bs of 0.6–0.8 T which changes regularly with the content variations of P, B and Si. By ascertaining applicability of the empirical GFA criterions, Trg, α, β and γ can be used in evaluating the GFA of FeNiBSiPNb system alloys.

Synthesizing and Characterizing of a Novel Zr90Ni6Pd4 Bulk Metallic Glassy Alloy Obtained by Spark Plasma Sintering of Mechanically Alloyed Powders

A single phase of metallic glassy Zr90Ni6Pd4 powders was synthesized by mechanical alloying approach of the elemental powders, using a low-energy ball mill. The solid-solution hcp-ZrNiPd phase obtained after 25 h of the milling time transformed into a single amorphous phase upon ball milling for 100 h to 150 h. This synthesized amorphous alloy transformed into a metallic-glass at a glass transition temperature of 552.8°C. A small volume fraction of this glassy phase transformed into a mixture of two metastable phases of i-phase + big-cube upon annealing at 649.1°C. The supercooled liquid region of the metallic glassy Zr90Ni6Pd4 alloy powders was 69.7°C. A complete crystallization was achieved at a temperature ranged from 649.1°C to 682.2°C through a sharp exothermic reaction with an enthalpy change of crystallization of -76.3 J/g. After this temperature, the formed metallic glassy phase was transformed to polycrystalline mixture of tetragonal Zr2Ni and Zr2Pd phases. The powders obtained after 150 h of milling were subsequently consolidated at 600°C, using spark plasma sintering technique. The sizes of the obtained bulk metallic glassy buttons ranged were 15 mm and 50 mm in diameter with different thicknesses in the range between 0.25 mm to 20 mm. This consolidation step led to the formation of full-dense buttons with relative densities laid in the range between 99.23% to 99.76% without precipitations of any medium- or long-range ordered phase (s). Nanoindentation approach was employed to identify the nanohardness and Young’s modulus that were in the range between 7.74 to 9.32 GPa, and 135.26 to 151.15 GPa, respectively.

Cu Particulates Dispersed Bulk Metallic Glass Composites with High Strength and High Electrical Conductivity Fabricated by Spark Plasma Sintering

Using the mixed powders containing gas-atomized powders of metallic glassy alloys (Cu50Zr45Al5, Fe73Si7B17Nb3, Ni52.5Nb10Zr15Ti15Pt7.5) blended with high-conductive Cu particulates, we produced bulk metallic glassy alloy composites with high strength and high electrical conductivity, as well as with enhanced plasticity and satisfying large size requirements by a spark plasma sintering process. In this paper we present and review our research results on the fabrication and properties of the bulk glassy alloy composites by the spark plasma sintering process.

The onset of plasticity of a Zr-based bulk metallic glass

The deformation behaviors of a Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glassy alloy under step-controlled tensile loads have been studied in situ and systematically using scanning electron microscopy and synchrotron X-ray diffraction. A circular hole, as a stress concentrator, was introduced in the middle of the gauge length of the sample to facilitate the creation of shear bands in a controllable way at the edge of the hole in situ imaging and diffraction studies could be carried out at the identical loads in a quasi-steady state manner. Pair distribution function was used to calculate the strains of different atomic coordination shells and the relative change of the bond lengths of different atomic pairs. The combined imaging and diffraction studies revealed that (1) the extension of solvent–solvent (Zr–Zr) atomic pairs under tension causes the nucleation of shear bands, and (2) the compressive stress field around the shear band tip effectively slows down the fast propagation of shear bands.

Cryogenic treatment induced hardening of Cu45Zr45Ag7Al3 bulk metallic glass

Little is known about the mechanical properties of bulk metallic glassy alloys (BMGs) after cryogenic treatment (CT). Cu45Zr45Ag7Al3 BMGs were treated in cryogenic temperatures for four chosen holding times. Compared with the as-cast sample, the compressive fracture strength of this BMG increased with increasing CT time. Furthermore, the CT changes the fracture mode from the ductile to the brittle. And CT brought about the precipitation of the AlCu2Zr and Cu5Zr phases which were accompanying with the morphology modification and contributed to the mechanical properties improvement of this BMG.

Cryogenic treatment induced hardening for Cu-Zr-Ag-Al bulk metallic glasses

Little is known about the mechanical properties of bulk metallic glassy alloys (BMGs) after cryogenic treatment. In this study, the effects of cryogenic treatment (CT) on the microstructural transition and the mechanical properties of Cu-based bulk metallic glass (BMG) were studied. The results showed that submicron AlCu2Zr and Cu5Zr phases can precipitate from the Cu-Zr-Ag-Al matrix after 192 h CT. The formation of these nanometer-sized crystalline phases substantially enhanced the mechanical properties of the bulk amorphous alloy. The micro-hardness and the compressive strength were found to increase respectively from 501 HV and 1510 MPa to 595 HV and 1910 MPa after cryogenic treatment. CT is a promising approach to strengthening metal glasses.

Influence of viscous flow on the deformation behavior of bulk metallic glassy alloys in supercooled liquid region

We present the investigation of the effect of viscosity on the deformation behavior of metallic glasses at supercooled liquid region during hot extrusion. Also the change of the specific surface area in porous Hf-based metallic glass and Ni-based metallic glass were compared. The homogeneously distributed ruggedness-shape surface of ligament was observed in the Hf-based metallic glass which has lower viscosity comparing to that of Ni-based metallic glass. For lower viscosity, it is very desirable to fabricate large surface area porous metallic glass due to a change of the surface morphology of the ligaments from smooth-like to rugged-like appearance, thus suggesting an optimum regime for increasing the specific surface area by controlling viscosity of metallic glass at a given processing condition.

Thermal and Electrical Transport Properties of Zr-Based Bulk Metallic Glassy Alloys with High Glass-Forming Ability

Thermal and electrical transport properties, such as thermal diffusivity, the electrical resistivity and thermopower of the Zr-based bulk metallic glassy (BMG) alloys of Zr42Cu42Ag8Al8 and Zr55Al10Cu35−xNix (x = 0, 5 and 10) with high glass-forming ability were investigated. Thermal diffusivity is comparatively low at about 2 × 10−6 m2 s−1, reflecting the aperiodic crystal structure of the BMG, whereas it becomes higher and depends on the alloy compositions after their crystallization. The phonon contribution to the thermal conductivity of the BMG alloys is thought to be small, based on a comparison with the estimated value of the electronic contribution to the thermal conductivity from the Wiedemann–Franz law. The thermopower of the present Zr-based BMG alloys shows a small positive value around room temperature, which is a general feature of nonmagnetic amorphous alloys.

Unique metallurgical microstructures and characteristics of nano-amorphous state bulk alloys formed under high gravity by very high speed centrifugal casting

ABSTRACTAn innovative “Rapid-Solidification Centrifugal Casting (RSCC) Process” was applied to manufacturing more high functional Fe-based magnetic alloys and some amorphous bulk metallic glassy alloys (BMGs) components. The molten alloys were poured into copper mold with rotation speed up to 6000rpm which can cause the maximum 4000 times as much centrifugal pressurization force as gravity. The bulk components of ring or very small three dimensional component samples of Fe and Zr alloy systems were successfully fabricated within only a few seconds at one process from melts with more cheap production cost. The molten raw BMG alloys (ZrAl system) and Fe-based soft-magnetic alloys(FeGaAl and FeSiB systems) by high frequency induction heating method were poured into copper mold. The fabricated BMG components of artificial tooth and ring of ZrAlNiCu alloy system are almost amorphous state by XRD profiles. Especially, the soft magnetic properties of two Fe-based alloys showed drastic change and were enhanced generally depending on the unique very fine, nano-scale columnar grains with strong texture toward radius direction for FeGaAl(Galfenol) alloy. The magnetization saturation Bs was enhanced up to1.97T in FeSiBPCu alloy. In consequence, according to synergistic effect of rapid solidification and high pressurization casting in this manufacturing process, RSCCP has the technical advantages of expansion of element composition, uniformity of the quality, reduction of internal defects and prevention of degradation at the time of secondary fabrication process of nano-crystalline-structured alloys and BMGs.

Effects of rare-earth elements on the glass-forming ability and mechanical properties of Cu46Zr47−x Al7M x (M = Ce, Pr, Tb, and Gd) bulk metallic glasses

Cu46Zr47−x Al7M x (M = Ce, Pr, Tb, and Gd) bulk metallic glassy (BMG) alloys were prepared by copper-mold vacuum suction casting. The effects of rare-earth elements on the glass-forming ability (GFA), thermal stability, and mechanical properties of Cu46Zr47−x Al7M x were investigated. The GFA of Cu46Zr47−x Al7M x (M = Ce, Pr) alloys is dependent on the content of Ce and Pr, and the optimal content is 4 at.%. Cu46Zr47−x Al7Tb x (x = 2, 4, and 5) amorphous alloys with a diameter of 5 mm can be prepared. The GFA of Cu46Zr47−x Al7Gd x (x = 2, 4, and 5) increases with increasing Gd. T x and T p of all decrease. T g is dependent on the rare-earth element and its content. ΔT x for most of these alloys decreases except the Cu46Zr42Al7Gd5 alloy. The activation energies ΔE g, ΔE x, and ΔE p for the Cu46Zr42Al7Gd5 BMG alloy with Kissinger equations are 340.7, 211.3, and 211.3 kJ/mol, respectively. These values with Ozawa equations are 334.8, 210.3, and 210.3 kJ/mol, respectively. The Cu46Zr45Al7Tb2 alloy presents the highest microhardness, Hv 590, while the Cu46Zr43Al7Pr4 alloy presents the least, Hv 479. The compressive strength (σ c.f.) of the Cu46Zr43Al7Gd4 BMG alloy is higher than that of the Cu46Zr43Al7Tb4 BMG alloy.

Mechanical behavior of metallic glasses Mg–Cu–Y using nano-indentation

The mechanical properties of amorphous bulk metallic glassy (BMG) alloy, Mg58Cu31Y11, are examined using nano-indentation scratching test. This study investigates the influences of different scratching conditions on the mechanical properties such as the friction force and the friction coefficient (μ) to understand the abrasive behavior of the BMG. The scratching conditions include applied normal load, depth of scratch, scratching velocity, and scratching temperature. The experimental results of the friction force, friction coefficient, hardness, and scratching morphology of BMG are characterized. The result shows that the friction force is nearly proportional to the normal load; and the friction force exhibits a slightly dependent on the scratching temperature. Then, regression analysis method is utilized to establish a formula to fit the scratching condition of BMGs. The regression analysis can be applied to model the mathematical relationship between the scratching parameters. The regression result shows a good agreement with experimental one.

Investigation of glass-forming ability, deformation and corrosion behavior of Ni-free Ti-based BMG alloys designed for application as dental implants

We developed new Ti-based bulk metallic glassy (BMG) alloys in Ti–Zr–Pd–Cu–Sn system without Ni element for application as biomaterials. These BMG alloys have a high potential to be applied as metallic biomaterials in various forms, such as melt-spun ribbons and cylindrical rods with a diameter of 4 mm. We also investigated of new Ti-based BMG alloys with higher glass-forming ability (GFA) for medical market as dental implants. These Ti-based BMG alloys do not contain Ni, Al and Be elements which are well known to be harmful for human body. In particular, a rod sample of the Ti 44.1Zr 9.8Pd 9.8Cu 30.38Sn 3.92Nb 2 BMG alloy with a diameter of 3 mm produced by copper mold casting exhibits a compressive strength of 1990 MPa and a Young's modulus of 99 GPa. In addition, the Ti 44.1Zr 9.8Pd 9.8Cu 30.38Sn 3.92Nb 2 BMG shows a large supercooled liquid region of 62 K and a reduced glass-transition temperature, T rg( = T g / T m) of 0.61. The high thermal stability of the supercooled liquid allowed the fabrication of cylindrical rod specimens up to 5 mm in diameter. Thus the studied alloy exhibits high glass-forming ability (GFA) and a large size enough to be used for dental implants. The Ti 44.1Zr 9.8Pd 9.8Cu 30.38Sn 3.92Nb 2 BMG alloy also has a high corrosion resistance and is passivated at the lower passive current density of approximately 10 − 2 A m − 2 , 10 − 3 A m − 2 and 10 − 2 A m − 2 , in 1 mass% lactic acid, PBS (phosphate-buffered saline without calcium and magnesium salts solution) and HBSS (Hank's balance salt solution without calcium, magnesium and phenol red), respectively, at 310 K, which are lower than those of pure Titanium and Ti–6Al–4V alloy.

Glass formability and fragility of Fe 61Co 9− xZr 8Mo 5W xB 17 ( x = 0 and 2) bulk metallic glassy alloys

The glass-forming ability (GFA) of Fe 61Co 9− x Zr 8Mo 5W x B 17 ( x = 0 and 2) alloys was investigated in terms of the temperature interval of the melting process Δ T m, the reduced glass transition temperature T rg, the modified GFA parameter γ m, as well as the packing density ρ meas/ ρ cal. The GFA parameters indicate that tungsten increases the glass formability of the alloys. The fragility of the alloys was discussed according to the Vogel–Fulcher–Tamman (VFT) equation, showing the fragility indexes of 47 and 39 for tungsten contents of 0 and 2 at.%, respectively. The role of the tungsten in the alloys has been discussed from the minor addition technological point of view.

Laser surface coating of Fe–Cr–Mo–Y–B–C bulk metallic glass composition on AISI 4140 steel

Fe-based bulk metallic glasses exhibit very high hardness, elastic modulus/limit and wear/corrosion resistance. In the present investigation, an attempt has been made to develop an amorphous coating with Fe 48Cr 15Mo 14Y 2C 15B 6 bulk metallic glass on AISI 4140 substrate by laser surface processing. Following coating, the microstructure and phase aggregate were analyzed by scanning electron microscope and X-ray diffraction, respectively. Microhardness and wear resistance were assessed using Vickers microhardness tester and ball-on-plate wear testing machine, respectively. The coating thickness varied directly with incident laser power and interaction time. Despite trials with wide range of process parameters, the present experiments were unable to retain complete amorphous surface microstructure after laser surface coating. Numerical prediction of the thermal profile and related parameters suggest that the cooling rate and thermal gradient experienced by the coated zone were fairly high. Yet failure to retain amorphous/glassy microstructure of an otherwise bulk metallic glassy alloy suggests that compositional changes (solute redistribution) within the coated zone and across the coating–substrate interface are responsible for nucleation and growth of crystalline phases from the melt. However, correlation between coating parameters and surface microstructure and properties allowed determination of the optimum conditions that ensured fine grained uniform microstructure with a significant improvement in hardness and wear resistance.

Fabrication of Ni-free Ti-based bulk-metallic glassy alloy having potential for application as biomaterial, and investigation of its mechanical properties, corrosion, and crystallization behavior

A new Ti-based bulk-metallic glassy (BMG) alloy without Ni was developed in various forms such as melt-spun ribbon and cylindrical rods. Ti metal and Ti-based alloys are well known as biomaterials because Ti has good biocompatibility with the human body. We examined mechanical and chemical properties of a newly developed Ti-based BMG alloy in comparison with pure Ti metal and Ti–6Al–4V alloy, which are used for biomaterials. The new Ti-based BMG (Ti45Zr10Pd10Cu31Sn4) alloy does not contain Ni, Al, and Be elements, which are known to be toxic. The Ti45Zr10Pd10Cu31Sn4 BMG alloy rod with a diameter of 3 mm, which is produced by copper mold casting, exhibits a compressive strength of 1970 MPa and a Young’s modulus of 95 GPa. In addition, the Ti45Zr10Pd10Cu31Sn4 BMG alloy shows a supercooled liquid region of 56 K and a reduced glass-transition temperature, Trg(=Tg/Tl), of 0.56. The high thermal stability of supercooled liquid has enabled the fabrication of a cylindrical rod specimen with a diameter of 4 mm. This alloy exhibits precipitation of a primary nanoscale icosahedral phase upon devitrification followed by the formation of a metastable unidentified phase. Ti2Cu and Ti3Sn are stable phases formed in this alloy. The Ti45Zr10Pd10Cu31Sn4 BMG alloy has a high corrosion resistance and is passivated at a lower passive current density of approximately 10−2 A/m2 compared to those of pure titanium and the Ti–6Al–4V alloy in 1 mass% lactic acid and phosphate-buffered saline solutions at 310 K.