Bulk Zr-Al-Cu-Ni alloys were produced by die casting into a copper mold under Aratmosphere. The microstructure of fully amorphous as well as partially crystalline samples was analyzed by X-ray diffraction (XRD), scanning (SEM) and transmission electron microscopy (TEM), and chemical analysis with special emphasis on the size and composition of the crystallites. The mechanical behavior of the different samples was investigated by constant compression rate tests. At room temperature the samples show inhomogeneous deformation and, independent of the chosen composition, relatively low Young's moduli of about 70 GPa, flow stresses around 2 GPa and elastic strains of up to 3 %. Fully amorphous samples show microplasticity of up to 2 % strain without significant work hardening while specimens with a fairly high volume fraction of crystalline phases are extremely brittle. In contrast, at high temperatures around the glass transition temperature T8 both amorphous and partially crystalline specimens exhibit at low strain rates homogeneous deformation with an initial stress overshoot followed by an extended region of plastic flow. As compared to room temperature, the peak stresses are much lower and are hardly influenced by the presence of small volume fractions of crystalline phases. The observed thermal stability against crystallization provides a promising possibility for easy shaping of complex parts at temperatures around Tg.

Bulk nanocrystalline alloys with good ductility and high tensile strength (σ f) in Zr-Al-Cu- Pd and Zr-Al-Cu-Ni-Ti systems were formed by partial crystallization of cast bulk amorphous alloys. The nanostructure alloys consist of Zr2(Cu, Pd) or (Zr, Ti)2Al surrounded by the remaining amorphous phase. The particle size and interparticle spacing of their compounds are less than 10 and 2 nm, respectively. The crystallization of a Zr60Al10Cu30 amorphous alloy occurs by the simultaneous precipitation of Zr2Al and Zr2Cu with a large particle size of 500 nm and hence the addition of Pd or Ti is effective for formation of the nanostructure. The Pd or Ti has much larger negative heats of mixing against Zr or Al, respectively, and the Zr-Pd or Ti-Al atomic pair seems to act as preferential nucleation sites leading to the primary precipitation of Zr2(Cu, Pd) or (Zr, Ti) 2Al. The nanostructure alloy cylinders of 2 to 3 mm in diameter keep good ductility in the volume fraction (Vf) range of the compounds below 40 %. The σ f and Young's modulus (E) increase from 1760 MPa and 81.5 GPa, respectively, at Vf=40 % to 1880 MPa and 89.5 Gpa, respectively, at Vf =40 % for the Zr60Al10Cu20Pd10 alloy and from 1830 MPa and 89.0 GPa, respectively, at Vf =0 % to 1940 MPa and 95.2 GPa, respectively, at Vf =28 % for the Zr53Al12Cu20Ni10Ti5 alloy. The formation of the bulk nanostructure alloys with high σ f is presumably due to the reentrance of free volumes into the remaining amorphous phase caused by quenching from the supercooled liquid region.

The samples of Zr56Al9Cu5Ni30 alloy were prepared by liquid-quenching. The mechanical properties depend on the cooling condition. The Hv value (25g load) is 580 for slow cooled rate sample, whereas the Hv value is over 800 for fast cooled sample. Since the fast cooling enhances the sample hardness, these samples become brittle. The brittleness is evaluated by the critical deformation energy (Ec) of collapse.

Structure, glass forming ability and soft magnetic properties for Fe-Al-Ga-P-C-B glassy alloy system were investigated in the compositional range of Fe from 69 to 78 at%, (Al+Ga) from 2 to 12 and (P+C+B) from 17 to 28. The saturation magnetization (σ5) rises gradually with increase of Fe concentration. The maximum value of 70K for supercooled liquid region (ΔTx=Tx-Tg, Tx: crystallization temperature, Tg: glass transition temperature:) and the maximum thickness of 180 μm for glass formation (tmax,) are found in the composition range around Fe=70at% and (Al+Ga)=7at%. The highest permeability (μc) of 20,000 at 1kHz and the lowest coercive force (Hc) of 2 A/m at the sample thickness of 30 μm can be also obtained at this composition. It was ascertained that the composition regions to yield the maximum glass forming ability and lowest magnetostriction were in agreement with that in which the most excellent soft magnetic properties were yielded. This results allow us to assume that the excellent soft magnetic properties for this glassy alloy system in the limited composition range are presumably due to high structural homogeneity resulting from significantly high glass-forming ability.

The passivation behavior of bulk glassy Zr55Al10Cu30Ni5 alloy samples in weakly alkaline sulphate solution (pH = 8) is investigated in comparison to the arc-melted crystalline alloy, to the main alloying component zirconium and to aluminium. Results of potentiodynamic and potentiostatic polarization measurements reveal the formation of a stable passivating surface film on the glassy alloy grown by a high-field mechanism. Auger electron spectroscopic investigations of anodized sample surfaces show that the films formed on the glassy Zr-Al-Cu-Ni alloys exhibit a composition gradient in cross-sectional direction. In 0.001M NaCl electrolytes bulk glassy Zr-Al- Cu-Ni samples are susceptible to pitting corrosion, which is due to the existence of crystalline inclusions.

In this investigation depth profiling by Ar+ ion sputtering in combination with x-ray photoelectron spectroscopy was used to determine the thickness and the chemical composition of the oxide layers formed on the bulk metallic glass Zr46.75Tig8.25Cu7.5Ni10Be27.5 (V4) under different preparation conditions. The thickness of the oxide layer was in the range between 4 nm and 30 nm for samples oxidized in air at room temperature and annealed in air at 573 K for 15 hours, respectively. The oxide layers showed an enrichment of Be at the outermost surface followed by a Be, Zr and Ti rich phase. Cu and Ni are depleted within the whole oxide layer. BeO, ZrO2 and various Ti oxides were detected in the oxide layer, whereas Cu and Ni occurred only in a non-oxidized zerovalent state. Our data indicate that the oxidation is controlled by the inward and outward diffusion of the metallic components.

Binary Zr-(Cu, Ni, Al) alloys were mechanically intermixed by cold-rolling stacks of elemental foils. The results indicate that solid-state amorphization is initiated if the grain size of the Zr-Cu and Zr-Ni alloys falls below a critical value. Amorphization was not observed for the Zr-Al alloy. These results are in accordance to the predictions of a model for solid-state amorphization. The comparison with the results on a quaternary Zr-Cu-Ni-Al alloy indicate the influence of multicomponent alloying on the glass-forming ability of Zr-rich alloys by mechanical working.

We have measured the shear modulus and its temperature dependence of Pd40Ni40P20 using an EMAT technique. The room temperature value of 3.92(1011) d/cm2 is in fair agreement with that of 3.66(1011) d/cm2 given earlier by He and Schwarz, using a resonant ultrasound spectroscopy technique. The relative change with temperature coefficient for T << Tg is 3.4(10−4) K−1. For the heating rate of ∼1 K/min used here, Tg = 565 K compared with a value of 575 K reported earlier. The shear modulus is continuous at Tg , but its temperature coefficient is larger by a factor of 6.5 for T >> Tg. During temperature cycling near but below Tg , irreversible aging effects are found showing that the amorphous state is not an equilibrium state. Near but above Tg, the cycling effects are reversible for time scales of the order of hours but not for time scales of the order of days, showing that metastable equilibrium states have not yet been fully attained. The results are in overall agreement with the predictions of the Interstitialcy Theory.

The fracture behavior of a Zr-based bulk amorphous alloy, Zr-10 Al-5 Ti-17.9 Cu-14.6Ni (at.%), was examined by transmission electron microscopy (TEM) and x-ray diffraction forany evidence of crystallization preceding crack propagation. No evidence for crystallizationwas found in shear bands in compression specimens or at the fracture surface in tensile specimens.In- situ TEM deformation experiments were performed to more closely examine actualcrack tip regions. During the in-situ deformation experiment, controlled crack growth occurredto the point where the specimen was approximately 20 μm thick at which point uncontrolledcrack growth occurred. No evidence of any crystallization was found at the crack tips or thecrack flanks. Subsequent scanning microscope examination showed that the uncontrolledcrack growth region exhibited ridges and veins that appeared to have resulted from melting. Performing the deformations, both bulk and in-situ TEM, at liquid nitrogen temperatures (LN2) resulted in an increase in the amount of controlled crack growth. The surface roughness of the bulk regions fractured at LN2 temperatures corresponded with the roughness of the crack propagation observed during the in-situ TEM experiment, suggesting that the smooth-appearing room temperature fracture surfaces may also be a result of localized melting.

Light emitted during rupture of Zr41.2Ti13.8Cu12.5 Ni10Be22.5 (at%) bulk metallic glass has been investigated. Charpy V-notch specimens fractured in a pendulum impact apparatus were used to excite light emission. Spectra acquired from rupture in air exhibited a single broad peak and were fit to a blackbody temperature of ∼3175 K. In nitrogen, however, light emission was no longer visible to the eye. In this case, the captured light was at least four orders of magnitude less intense, and spectra were shifted to the red with an effective blackbody temperature of ∼1400 K. Fracture surfaces generated in both air and nitrogen exhibited local melting, providing further evidence of intense heating during fracture. Based on these observations we argue that the intense light emission in air is associated with pyrolysis of fresh material exposed during rupture. Results were compared to preliminary observations of light emission from ribbons of a Zr57Nb5Ni12.6Cu15.4Al10 (at%) glass.

The advent of multi-component metallic alloys, which exhibit relatively good glass forming ability, has opened opportunities for processing metallic glasses into thick cross section components. The relatively good glass forming ability is important because conventional processing techniques (e.g., casting, extrusion and rolling) may be used to fabricate useful shapes while retaining the excellent engineering properties of an amorphous structure. In particular, the favorable processing characteristics of bulk amorphous alloys are the low cooling rates which can be exercised to yield an amorphous structure and the operating temperature range between the glass transition temperature (Tg) and the crystallization temperature (Tx). Current work is focused on developing a processing strategy that will allow us to fabricate even larger cross section amorphous alloys than are currently achievable by casting methods. The technique involves producing high pressure gas atomized (HPGA) Cu48Ti34Zr10Ni8 powders and consolidating them at temperatures above Tg, but below Tx. Thermal analysis of atomized powders by DSC provides details of the influence of powder particle size, which is related to cooling rate during atomization. The results of experiments characterizing the thermal and kinetic behavior of Cu48Ti34Zr10Ni8 powders indicate that short processing times are required to retain the amorphous structure during consolidation in the temperature regime between Tg and Tx.

Using a newly developed temperature modulated differential scanning calorimetry (TMDSC), glass transition has been detected in several RE-Fe-Al (RE = ND, Pr, Sm and Y) metallic glasses, which can not be observed by a conventional DSC. Our results show that the glass transition occurred together with a small fraction crystallization in the as-spun samples, the final main crystallization transition occurred at higher temperature (over 720K) in these rare-earth based alloys. Large undercooled liquid regions up to 200K at a underlying heating rate of 5K/min have been observed in these glasses.

When a eutectic alloy melt is undercooled well below its liquidus T1, liquid state phase separation occurs. The liquid morphologies can be frozen by subsequent crystallization. It was found that for Pd82Si18 when rapid quenching is also employed, ore of the phase-separated liquids after solidification is amorphous. The undercooled specimen is in bulk form with a diameter of ∼ 5 mm.

The enthalpy, entropy, specific heat, specific volume and the equilibrium shear viscosity of the deeply undercooled melt of the bulk glass forming alloy Pd40Ni40P20 have been determined as functions of temperature. The concept of limiting fictive temperature was applied to the entire set of measurements in order to allow for a valid comparison of the data based upon the respective equilibrium values. The comparison of the equilibrium properties shows that a proposed hierarchy of stability limits does not apply for this alloy. The results also indicate that the glass temperature as defined by the limiting fictive temperature does not depend on the property under observation.

The high thermal stability of bulk metallic glass (BMG) forming liquids in the undercooled state allows for measurements of thermophysical properties in a large time and temperature window. In this contribution, results on viscous flow, relaxation and crystallization of Zr-Ti-Cu- Ni-Be BMG forming alloys are presented. The data are compared with the kinetics of other metallic and non-metallic liquids. BMG formers are relatively strong liquids with melt viscosities that are about three orders of magnitude larger than in pure metals and other alloys. The strong liquid behavior of these alloys is also reflected by a small entropy of fusion and a weak temperature dependence of the thermodynamic functions upon undercooling. The high viscosity and small driving force for crystallization are major contributing factors to the high glass forming ability and low critical cooling rate. The upper portions of experimental timetemperature- transformation diagrams down to the crystallization nose can be described well using the kinetics deduced from the viscosity data. For lower temperature the viscosity can not describe the crystallization kinetics. The time scale for structural relaxation becomes larger than for diffusive hopping processes. Diffusion stays relatively fast, whereas viscosity and structural relaxation time upon undercooling follow a Vogel-Fulcher-Tammann relation.

The aim of the present paper is to analyse the glass formation and stability of bulk metallic glasses. Attention is focused to metallic alloys as systems which may develop a large glassforming ability. Glass formation when quenching from the liquid state is discussed in terms of the thermodynamics and kinetics of the stable/metastable competing phases. Thermodynamics is required to relate glass transition temperature, Tg, to the energetics of the supercooled liquid. Kinetic destabilisation of equilibrium solidification and, consequently, glass forming ability are favoured by the high viscosity values achieved under continuous cooling. The relative thermal stability of the supercooled liquid depends on the thermodynamic driving force and interfacial energy between each competing nucleating phase and the molten alloy. It is shown that the quantities representative of the process, once scaled, have a temperature dependence that is mostly fixed by the reduced glass transition temperature, Tgr= Tg/Tm, Tm being the melting temperature. Based on the classical models of nucleation and crystal growth, the reduced critical cooling rate is shown to follow master curves when plotted against Tgr. Experimental trends for specific systems are compared to predicted values from these master curves.

Results of calorimetric, differential thermal analysis, and structural measurements are presented for a series of bulk metallic glass forming compositions in the Zr-Ti-Cu-Ni-Be alloy system. The structural data identify the competing crystalline phases, formed on cooling from the liquid state, for various compositions in the Zr-Ti-X quasi-ternary phase diagram; with the Cu-Ni-Be ratio given by X = Be9Cu5Ni4. For this region of the ndimensional phase space (n=5), the bulk glass forming range is extensive and the calorimetric data exhibit thermal features associated with the occurrence of phase separation in the undercooled liquid state prior to primary crystallization. The topology of the composition manifold is complex; manifest by dramatic changes in crystallization behavior for small changes in the Zr-Ti-X ratio. Alloys with large supercooled liquid regions, Δ, are observed; ΔT≈ 135 K. Zr-Ti-Cu-Ni-Be alloy compositions with eutectic temperatures less than that of pure Al (Tm = 933 K) were also synthesized.

Since an amorphous phase in Au-Si system was synthesized for the first time by rapid solidification in 1960[1], a large number of amorphous alloys have been prepared by various rapid solidification techniques. As the main amorphous alloy systems, one can list up the noble metal-, Fe-, Co-, Ni-, Ti-, Zr-, Nb-, Mo-, lanthanide(Ln)-, Al- and Mg-based alloys. Among these alloy systems, Fe-[2], Co-[2] and Al-[3]based amorphous alloys have been used in application fields of magnetic and high specific-strength materials. Thus, Fe- and Co-based amorphous alloys have gained the most important position as engineering amorphous alloys. When special attention is paid to Fe-based amorphous alloys, Fe-P-C alloys were synthesized in 1967[4] as the first Febased amorphous alloy. Subsequently, engineering important (Fe,Co)-Si-B amorphous alloys have been developed in 1974[5][6], followed by the formation of (Fe,Co,Ni)-(Cr,Mo,W)-C in 1978[7], (Fe,Co,Ni)-(Zr,Hf) in 1980[8] and then (Fe,Co,Ni)-(Zr,HfNb)-B amorphous alloys in 1981[9]. The (Fe,Co)-Si-B amorphous alloys have been used in many application fields as soft magnetic materials[2]. However, after 1981, nobody have succeeded in finding a new amorphous alloy in Fe- and Co-based systems by rapid solidification from liquid phase. Besides, all these amorphous alloys have serious disadvantages that high cooling rates above 105 K/s are required for glass formation and the resulting sample thickness is limited to less than about 50 μm[ 10]. Great efforts have been devoted to find Fe- and Co-based amorphous alloys with a high thermal stability of supercooled liquid against crystallization and a high glass-forming ability (GFA). Very recently, we have succeeded in finding new ferromagnetic bulk amorphous alloys with critical sample thicknesses ranging from I to 15 mm in Fe-(AI,Ga)-(P,C,B,Si)[11]-[14], (Fe,Co,Ni)-(Zr,IHf,Nb)- B[15]-[17], (Fe,Co)-(Zr,Hf)-(Nb,Ta)-(Mo,W)-B[18], (Fe,Co)-Ln-B[19] (Ln=lanthanide metal) and (Nd,Pr)-Fe-Al[20]-[22] systems. In this review, we present the formation, thermal stability, mechanical strength and magnetic properties of these new ferromagnetic bulk amorphous alloys.

The crystallization behavior of the bulk glass forming Zr41Ti14Cu12Ni10Be23 liquid was studied under different heating and cooling rates. Investigations were performed in high purity graphite crucibles since heterogeneous surface nucleation at the container walls does not effect the crystallization of the bulk sample. A rate of about 1 K/s is sufficient to circumvent crystallization of the melt while cooling from the equilibrium melt. In contrast, upon heating a rate of more than 150 K/s is necessary to avoid crystallization of Zr41Ti14Cu12Ni10Be23 samples. The difference between the critical heating and cooling rate is discussed within classical nucleation theory and diffusion limited crystal growth. The calculated difference of the critical heating and cooling rate can be explained by the fact that nuclei formed during cooling and heating are expose to different growth rates.

We have studied self-diffusion in the bulk metallic glasses Zr46.75Ti8.25Cu7.5Ni10Be27.5 and Zr65Cu17.5Ni10A17.5 by means of the radiotracer method. Diffusion of 63Ni has been investigated as a function of temperature in both alloys and also as a function of hydrostatic pressure in Zr46.75Ti8.25Cu7.5Ni10Be27.5. With the isotope 95Zr diffusion studies of the major component Zr were performed in Zr46.75Ti8.25Cu7.5Ni10Be27.5. The diffusivity of 95Zr is much smaller than that of 63Ni. The temperature dependence of 63Ni self-diffusion into Zr46.75Ti8.25Cu7.5Ni10Be27.5 and into Zr65Cu17.5Ni10A17.5 cannot be described by a single set of Arrhenius parameters, breaks in the Arrhenius curves are observed. We attribute the non-linear Arrhenius behaviour to the transition from the glassy to the supercooled liquid state. For the first time activation volumes of diffusion in a supercooled melt have been determined. From the pressure dependence of 63Ni diffusion in Zr46.75Ti8.25Cu7.5 Ni10Be27.5 we get activation volumes around one mean atomic volume favouring a diffusion mechanism via vacancy-like defects.