Bulk Glassy Alloys Research Articles

Formation and mechanical properties of Zr-Cu-Al bulk glassy alloys

Abstract We used highly purified elements (i.e. low-oxygen-content Zr metal) and a special arc melting and casting furnace to prepare Zr 50 Cu 40 Al 10 rod-shaped bulk glassy alloy over 10 mm in diameter. In the Zr-Cu-Al alloy system, we examined the glass-forming ability in the bulk glassy state by Δ T x , T g / T l , and the Hruby factor. The Hruby factor is appropriate for evaluating glass-forming ability in the cast Zr-Cu-Al bulk glassy alloy. In order to enhance the mechanical properties even in pre-oxidized Zr-Cu-Al (oxygen concentration 1000 ppm) bulk glassy alloy, we examined the effectiveness of a small addition of a fourth element. As a result, we found that the effect of adding the fourth element depends on the periodicity in the periodic table, i.e. the chemical interaction with Zr, Cu and Al elements.

Formation, thermal and mechanical properties of bulk glassy alloys in Zr–Al–Co and Zr–Al–Co–Cu systems

New Zr-based bulk glassy alloys in Zr–Al–Co and Zr–Al–Co–Cu systems were developed. The largest supercooled liquid region is upto 64 K for the Zr55Al20Co25 alloy and 80 K for the Zr55Al20Co20Cu5 alloy, respectively. Glassy rods with a diameter of 3 mm for the Zr55Al20Co25 alloy and 5 mm for the Zr55Al20Co20Cu5 alloy can be prepared by copper-mold casting. Glassy Zr55Al20Co20Cu5 sheet with a thickness of 2 mm was also formed by squeeze copper-mold casting. The bulk glassy Zr55Al20Co20Cu5 alloy exhibits Young’s modulus of 92 GPa, elastic limit of 2.1%, tensile strength of 1960 MPa, compressive fracture strength of 2200 MPa, and compressive plastic strain of 0.6%. The tensile strength value is considerably higher than those for the other Zr-based bulk glassy alloys reported upto date. The synthesis of the new Zr-based bulk glassy alloys with high glass-forming ability and high tensile strength approaching 2000 MPa is expected to result in a future extension of application fields as a high strength material.

Formation and mechanical properties of Zr$z.sbnd;Cu$z.sbnd;Al bulk glassy alloys

We used highly purified elements (i.e. low-oxygen-content Zr metal) and a special arc melting and casting furnace to prepare Zr 50 Cu 40 Al 10 rod-shaped bulk glassy alloy over 10 mm in diameter. In the Zr-Cu-Al alloy system, we examined the glass-forming ability in the bulk glassy state by Δ T x , T g / T l , and the Hruby factor. The Hruby factor is appropriate for evaluating glass-forming ability in the cast Zr-Cu-Al bulk glassy alloy. In order to enhance the mechanical properties even in pre-oxidized Zr-Cu-Al (oxygen concentration 1000 ppm) bulk glassy alloy, we examined the effectiveness of a small addition of a fourth element. As a result, we found that the effect of adding the fourth element depends on the periodicity in the periodic table, i.e. the chemical interaction with Zr, Cu and Al elements.

Electron-beam welding of Zr50Cu30Ni10Al10 bulk glassy alloys

By using a conventional electron-beam welding machine, an electron-beam welding of Zr 50 Cu 30 Ni 10 Al 10 bulk glassy plates has been achieved in the welding condition leading to the suppression of heat affected zone (HAZ). In order to obtain the cooling rate, which is sufficient for glass formation, the welding speed was controlled to be higher than 100 mm/s and the beam-radiated area should be limited to be smaller than 1 mm in diameter. The mean value of joint strength of the welded bulk glassy plate is about 1400 MPa, which is lower by 15% than the tensile strength (1650 MPa) of the glassy alloy. The fracture of the welded alloy plate occurs along shear slip plane across the welded area, reflecting good ductility in the welded area of the Zr 50 Cu 30 Ni 10 Al 10 bulk glassy alloy.

Glass transition and crystallization of Mg–Ni–Nd metallic glasses studied by temperature-modulated DSC

Glass transition and crystallization behavior of several Mg–Ni–Nd metallic glasses has been systematically studied by temperature-modulated differential scanning calorimetry (TMDSC). The glass transition transformation of alloys Mg 75Ni 10Nd 15 and Mg 77Ni 18Ni 5, which cannot be detected in conventional differential scanning calorimetry (DSC) heating scans, was observed through TMDSC measurements. It was concluded that the signal of the glass transition on the DSC scans overlapped with the relatively large heat release from the primary crystallization of either intermetallic Mg 3Nd phase in glassy Mg 75Ni 10Nd 15 alloy or Mg 2Ni phase in amorphous alloy Mg 77Ni 18Ni 5. Increasing the content of Ni in alloy Mg 75Ni 10Nd 15 can suppress the precipitation processes of Mg 3Nd, and results in the appearance of glass transition transformation on DSC heating curves. This confirmed and verified our TMDSC measurements. Clear observation of glass transition and understanding of crystallization micro-mechanism in such alloys can offer us new alloying and processing strategies for the preparation of bulk glassy alloys and development of new nanocrystalline/amorphous composite materials.

Formation of Ca–Mg–Zn bulk glassy alloy by casting into cone-shaped copper mold

Formation of Ca–Mg–Zn bulk glassy alloy by casting into cone-shaped copper mold

Formation of Ca–Mg–Zn bulk glassy alloy by casting into cone-shaped copper mold

A new Ca–Mg–Zn alloys having significantly improved glass-forming ability (GFA) has been developed. The ternary Ca65Mg15Zn20 bulk metallic glass with diameter of at least 15 mm is successfully fabricated by conventional copper-mold casting method in air atmosphere. The critical cooling rate for glass formation in the cone-shaped copper mold is less than 20 K/s. When compared with the GFA of Ca–Mg–M (M: Cu, Ni, and Ag) alloys, the significantly improved GFA of the Ca–Mg–Zn alloy cannot be represented by ΔTx, Trg, K, and γ parameters.

Recent progress in bulk glassy, nanoquasicrystalline and nanocrystalline alloys

This paper deals with recent progress in stabilized supercooled liquids (SLs) and the resulting bulk glassy, nanoquasicrystalline and nanocrystalline alloys which were mainly conducted by Sendai group in Japan. In this review, the following contents are focused on: bulk metallic glassy alloy systems, empirical rules for the achievement of high glass-forming ability (GFA), local atomic configurations, computational analyses, thermodynamic analysis, mechanical properties, soft magnetic properties, micro-forming ability, application, science and engineering importance and future trend of bulk glassy alloys including SL. As demonstrated in this review, the high stabilization of metallic SLs has already opened up new basic science and engineering application fields and its importance is strongly expected to increase more and more hereafter.

Bulk glassy Ni(Co–)Nb–Ti–Zr alloys with high corrosion resistance and high strength

Abstract Bulk glassy Ni 60− x Co x Nb 20 Ti 10 Zr 10 ( x =0–20 at.%) alloys with a large supercooled liquid region of more than 40 K were formed by copper-mold casting. The alloys with 5 and 10 at.% cobalt possess the highest glass-forming ability in the present alloy system and their critical diameter for glass formation is 1.5 mm. The bulk glassy alloys with different cobalt contents exhibit nearly the same corrosion behavior in HCl solutions. Their corrosion rates are less than 10 −3 mm per year in 1 N and 6 N HCl solutions. The bulk glassy alloys are spontaneously passivated with low passive current densities of around 10 −1 A m −2 in 1 N and 6 N HCl solutions. XPS analysis revealed the formation of a niobium-enriched passive film on the alloys by air-exposure or immersion in the acids, which could be responsible for the high corrosion resistance of the glassy Ni-based alloys. The Vickers hardness, Young’s modulus, compressive fracture strength and compressive fracture elongation of the 1.5 mm diameter bulk glassy alloys are 860, 160 GPa, 3050 MPa and 2% respectively. The facture surface exhibits a vein-like morphology.

Temperature dependence of heat capacity and electrical resistivity of Zr-based bulk glassy alloys

Abstract The specific heat at constant pressure ( C p ) and electrical resistivity ( ρ ) of Zr 55 Al 10 Cu 35 , Zr 55 Al 10 Cu 30 Ni 5 and Zr 55 Al 10 Cu 25 Ni 10 bulk glassy alloys were measured in the temperature range below 300 K. It was found that the measured C p of the Zr 55 Al 10 Cu (35− X ) Ni X ( X =0, 5 and 10 at.%) alloys are almost the same. The coefficient of electronic specific heat ( γ exp ) and the Debye temperature ( θ D ) of the Zr 55 Al 10 Cu 30 Ni 5 alloy were found to be 4.05 mJ mol −1 K −2 and 278 K, respectively. The ρ of the Zr 55 Al 10 Cu 35 Ni 5 alloy increased as the temperature decreased in the temperature range between approximately 2.8 and 300 K. The ρ of the alloy with the X =5 decreased abruptly below approximately 2.8 K. The ρ of the Zr 55 Al 10 Cu 35 and Zr 55 Al 10 Cu 25 Ni 10 alloys increased with decreasing temperature in the temperature range between 1.8 and 300 K.

Preparation of bulk amorphous Fe–Cr–Mo–Ga–P–C–B alloys by copper mold casting

The Fe 77.5− x − y − z Cr x Mo y Ga z P 12 C 5 B 5.5 bulk glassy alloy was prepared in the shape of rods and ribbons using copper mold casting and melt spinning, respectively. The structure was investigated by X-ray diffraction (XRD) and the thermal stability was checked by differential scanning calorimetry (DSC). It was found that the samples consist of an a single amorphous phase and exhibit a rather wide supercooled liquid region before crystallization. Some characteristic thermal properties of the amorphous samples as a function of the geometrical dimensions are discussed, as well as the dependence of the glass-forming ability on composition. Additionally, some magnetic data like coercivity H c , saturation polarization J s and Curie temperature T c are presented.

Ultra-high strength above 5000 MPa and soft magnetic properties of Co–Fe–Ta–B bulk glassy alloys

Glassy Co 43Fe 20Ta 5.5B 31.5 alloy rods with glass transition temperature of 910 K, followed by a large supercooled liquid region of 72 K were produced in the diameter range up to 2 mm by copper mold casting. The glassy alloy rods exhibit ultra-high fracture strength of 5185 MPa, high Young’s modulus of 268 GPa, high specific strength of 6.0 × 10 5 N m kg −1 and high specific Young’s modulus of 31 × 10 6 N m kg −1. The fracture strength, specific strength and specific Young’s modulus obtained by compression test are higher than all previous values reported for any crystalline and glassy alloys. The ultra-high strength of over 5000 MPa persists in the temperature range up to 698 K. The fracture occurred on one major shear band which was declined by 44° to the stress axis implying the slight deviation from the maximum shear stress plane. Excellent formability is manifested by large tensile elongation of 1400% and large reduction ratio in thickness above 90% in the supercooled liquid region. The ultra-high strength alloy exhibits simultaneously good soft magnetic properties: low coercivity of 0.25 A/m and an extremely high permeability of 550,000. The novel alloy is promising as a new ultra-high strength material with good deformability and soft magnetic properties.

Characterization of Crystalline Inclusions in Cast Bulk Zr-Cu-Ni-Al Glassy Alloy

In order to clarify intrinsic features of bulk glassy alloys, the structural control is the most significant factor. However, it is difficult to obtain a single glassy phase by conventional casting methods. Crystalline inclusions in Zr-based bulk glassy alloy are often seen on the fracture surface. Crystalline inclusions are easily formed in molten alloy state by inhomogeneous nucleation or impurities i.e. oxygen, magnesium dichloride and so on. In Zr 5 5 Cu 3 0 Ni 5 Al 1 0 bulk glassy alloy, most of the crystalline inclusions are probably considered as τ 3 type intermetallic compound with typical composition of Zr 5 1 Cu 2 8 Al 2 1 . The morphology of the crystalline inclusions is changed by the quantity of absorbed oxygen impurities in bulk glassy alloy.

Synthesis and Fundamental Properties of Cu-Based Bulk Glassy Alloys in Binary and Multi-component Systems

A glassy phase containing cubic phase particles with a size of 3-5 nm was formed in cast Cu 6 0 Zr 3 0 Ti 1 0 and Cu 6 0 Hf 3 0 Ti 1 0 bulk alloys. The cubic phase is in a metastable state and its lattice parameter (a 0 ) is 0.45 nm for the former alloy and 0.51 nm for the latter. These bulk alloys exhibit good mechanical properties of 2000-2130 MPa for tensile strength (σ 1 , f ), 2060-2160 MPa for compressive strength (σ c , f ) and 0.008-0.017 for compressive plastic strain (e c , p ). The temperature interval of the supercooled liquid (SL) region prior to crystallization is 37 K for Cu 6 0 Zr 3 0 Ti 1 0 and 67 K for Cu 6 0 Hf 3 0 Ti 1 0 . The primary crystallization occurred by precipitation of cubic CuZr (a 0 = 0.35 nm) in a diffusion-controlled growth mode of nuclei and an orthorhombic Cu 8 Hf 3 phase in an interface diffusion-controlled growth of nuclei with decreasing nucleation rate. The difference in the precipitation modes is interpreted to be the origin of the difference in the SL region. Furthermore, the addition of Al to Cu-Zr and Cu-Hf alloys caused the formation of a glassy single phase in the rod form with diameters up to at least 3 mm, though bulk glassy alloy rods with critical diameters up to 1.5 mm and σ c , f , of 1920-2260 MPa were formed in Cu-Zr and Cu-Hf binary systems. The ternary bulk glassy alloys exhibited high σ c , f of 2100-2370 MPa with e c , p of 0.002-0.006. The addition of Pd, Pt, Ag or Au increased ΔT x and a large ΔT x of 102-110 K was obtained for the Cu-Hf-Al-M (M=Pd or Ag) glassy alloys. The synthesis of Cu-based bulk glassy alloys with good mechanical properties and large ΔT x in glassy single, and mixed glassy and cubic phase states, is important for future applications of bulk glassy alloys.

New Cu-Zr-Al-Nb Bulk Glassy Alloys with High Corrosion Resistance

New Cu-based bulk glassy alloys with good mechanical properties were formed in Cu-Zr-Al-(Nb) system by copper mold casting. They exhibit a large supercooled liquid region (� Tx) of 50 K-74 K and high glass-forming ability with maximum diameters of 2.0 mm-3.0 mm. The addition of Nb to the glassy alloys is effective for improving the corrosion resistance in all the solutions. The corrosion rate of the 5 at% Nb alloy

Cu-Based Bulk Glass Formation in the Cu-Zr-Ga Alloy System and Their Mechanical Properties

The thermal stability, glass-forming ability (GFA) and mechanical properties of a new Cu-based glassy alloy in Cu-Zr-Ga ternary system have been investigated. The supercooled liquid region ΔT x (= T x - T g ) exceeding 40 Kand reduced glass transition temperature (T g /T l ) above 0.59 are obtained simultaneously in the composition range from 2.5 to 7.5%Ga and 37.5 to 42.5%Zr, and the highest T g /T l is 0.62 for Cu 5 2 . 5 Zr 4 2 . 5 Ga 5 and Cu 5 5 Zr 4 0 Ga 5 alloys. The Cu-based Cu-Zr-Ga glassy alloys are formed in a rod form with a diameter up to 2.0 mm by the copper mold casting. The bulk glassy alloys exhibit good mechanical properties of 550-580 for Vicker's hardness (H v ), 105-111 GPa for Young's modulus (E), 1910-2130 MPa for compressive fracture strength (σ c , f ), and 0.2-0.5% for plastic elongation. The GFA of Cu-based Cu-Zr-Ga glassy alloys is more closely related to T g /T l values rather than ΔT x . The present new Cu-based bulk glassy alloys are expected to be developed as another type of bulk structural material with higher strength combined with good ductility.

Formation of Porous Pd-based Bulk Glassy Alloys by a High Hydrogen Pressure Melting-Water Quenching Method and Their Mechanical Properties

Porous glassy Pd42.5Cu30Ni7.5P20 alloy rods of 7 mm in diameter and 50 mm in length were produced by melting the Pd-Cu-Ni-P alloy for 600 s at 853 K in a hydrogen pressure of 1.5 MPa and then water quenching. The pores have a nearly spherical shape and their average size is approximately 200 μm. The volume fraction of the pores was changed in the range of 0.36 to 0.64. The glass transition temperature and crystallization temperature of the porous alloy are 577 and 671 K, respectively, in agreement with those of the pore-free alloy. The porous alloy rod exhibits unique mechanical properties with the features of much higher ductility and flexibility which are significantly different from those for the pore-free alloy rod. The unique mechanical characteristics indicate the possibility of future uses as a new type of structural and functional materials.

Formation, Thermal Stability and Mechanical Properties of Aluminum-Based Glassy Alloys Containing Boron

Glassy type Al-based alloys, with a distinct glass transition and a supercooled liquid region before crystallization, were formed in (Al0.84Ni0.1Ce0.06)100−xBx (x = 0 to 10 at%) and (Al0.84Ni0.05Y0.09Co0.02)100−xBx (x = 0 to 3 at%) systems by melt spinning. The addition of an optimum amount of B was found to increase the temperature interval of supercooled liquid region from 18 K to 23 K at 6%B for the former system and from 28 K to 31 K at 1.5 and 2%B for the latter system. The similar increase with B content was also recognized for Vickers hardness (Hv) and tensile fracture strength (σf) and the highest values of Hv and σf are 400 and 1060 MPa, respectively, at 6%B and 375 and 1140 MPa, respectively, at 1.5%B. The maximum phenomena of temperature interval of supercooled liquid region (ΔTx = Tx — Tg), Hv and σf at optimum B contents can be interpreted in the framework of the three empirical component rules for the stabilization of supercooled liquid and the formation of bulk glassy alloys. The crystallization occurs through two stages of glass → Al + metastable phase → Al + Al3Ni + Al4Ce for the Al-Ni-Ce-6%B alloy and through three stages of glass → Al + glass → Al + metastable phase + glass → Al + Al9Co2 + Al3Y + Al4NiY + Al-Y-Ni-Co quaternary compound for the Al-Ni-Y-Co-2%B alloy. The finding of Al-based glassy alloys with large ΔTx values above 30 K is encouraging for future development of Al-based alloys as a high strength material with light weight.

Excellent Mechanical Properties of Cu-Hf-Ti-Ta Bulk Glassy Alloys Containing <i>In-Situ</i> Dendrite Ta-based BCC Phase

A glassy phase containing high volume fractions (Vf) of bcc Ta-based phase was formed in as-cast (Cu0.6Hf0.25Ti0.15)94Ta6 alloy rods with diameters up to 2 mm. Its Vf increased from 9.5 to 11% with increasing rod diameter from 1 to 2 mm. The in-situ bcc phase has a dendritic morphology with a size of about 10 μm and its size tends to increase with increasing Vf. The bcc phase has analytical compositions of 1.4 at% Cu, 7.6 at% Ti and 91.0 at% Ta. The lattice parameter of the bcc phase is 3.306 nm which approximates to that of Ta metal. The thermal stability of the remaining glassy matrix remains unchanged in coexistence with the bcc phase. The mixed structure is presumed to be formed by the primary precipitation of ductile dendritic bcc phase, followed by the solidification of the remaining liquid to glassy phase. The Young's modulus (E), yield strength (σy), true compressive fracture strength (σt,f) and true plastic strain (εp) were 104 GPa, 2125 MPa, 2100 MPa and 0.34, respectively, for the φ2 mm rod with 11% Vf. The σy and σt,f are higher than those (2010 MPa and 2005 MPa) for the Cu60Hf25Ti15 glassy alloy rod with a diameter of 2 mm. Especially, the εp for the (Cu0.6Hf0.25Ti0.15)94Ta6 mixed structure alloy is dramatically enhanced in comparison with that (εp = 0.016) for Cu60Hf25Ti15 single phase alloy. The enhancement of σy, σt,f and εp in the mixed structure of glassy and bcc phase for the new Cu-based system is promising for future uses as a new type of high-strength bulk glassy alloy.

Formation and Mechanical Strength of New Cu-Based Bulk Glassy Alloys with Large Supercooled Liquid Region

High-strength Cu-based bulk glassy alloys with a large supercooled liquid region in Cu-TM-Al (TM=Zr, Hf) ternary and quaternary systems were synthesized by copper mold casting. The maximum diameter was 3.0 mm for the Cu 5 0 Zr 4 5 Al 5 , Cu 5 2 . 5 Hf 4 0 Al 7 . 5 , Cu 5 0 Hf 4 2 . 5 Al 7 . 5 and Cu 5 0 Hf 2 2 . 5 Zr 2 2 . 5 Al 5 alloys. The glass transition temperature (Tg), temperature interval of supercooled liquid region ΔT x (=T x - T g ) and reduced glass transition temperature (T g /T l ) are in the range from 701-781 K, 54-91 K and 0.61-0.63, respectively. The Cu-based bulk glassy alloys exhibit good mechanical properties, i.e., 102-128 GPa for Young's modulus, 1885-2370 MPa for compressive fracture strength, up to about 0.6% for compressive plastic elongation, and 550-670 for Vickers hardness. The finding of the new Cu-based bulk glassy alloys with large supercooled liquid region above 54 K, high reduced glass transition temperature above 0.60, and high fracture strength above 1885 MPa is encouraging for future development as a new type of bulk alloys which can be used as structural materials.