We present the results of large scale computer simulations to discuss the structural and dynamic properties of silicate melts with the compositions (Na2O)(2·SiO2), (Na2O)(20·SiO2) and (Al2O3)(2·SiO2). We show that these systems exhibit additional intermediate range order as compared to silica (SiO2) where the characteristic intermediate length scales stem from the tetrahedral network structure. Furthermore we show that the sodium dynamics in the sodium silicate systems exhibits a very peculiar feature: the long–time decay of the incoherent intermediate scattering function can be described by a Kohlrausch law with a constant exponent β for q > qth whereby qth is smaller than the location of the main peak in the static structure factor for the Na–Na correlations.

We report about the preparation and properties of a Be-free Zr66.4Nb6.4Cu10.5Ni8.7Al8.0 alloy with a glassy or a nanocrystalline matrix and ductile bcc precipitates, which were developed with the aim to improve the mechanical properties. The samples were prepared in form of rods by injection casting into a copper mold. The phase formation as well as the resulting microstructure and the mechanical properties of the different samples have been investigated upon cooling from the melt at different quenching rates. The formation of the bcc phase embedded in a glassy matrix is strongly governed by the alloy composition and the actual cooling rate during solidification, because the glass forming ability is much lower compared to Zr-based alloys containing Be. Already small reductions in cooling rate lead to precipitation of additional crystalline phases. Compression tests reveal that the in-situ glassmatrix composite undergoes work hardening and plastic deformation prior to failure. Surprisingly, also a nanocrystalline matrix leads to high elastic strain values. These features significantly improve the mechanical behavior of the composites compared to the monolithic glass.

Melt-spun Zr64Al7Cu17Ni10Fe2 amorphous ribbons were milled under nitrogen atmosphere for different times. The resulting nitrided powders were studied by x-ray diffraction, Mössbauer spectroscopy and differential scanning calorimetry. The formation of nanosized crystalline particles, with cubic δ-ZrN structure, dispersed in the amorphous matrix was observed along with a change in the composition of the amorphous phase. Prolonged milling leads to the additional precipitation of late transition metals (Fe,Ni,Cu). The nitride particles affect the crystallization behavior and modify the thermal stability of the amorphous alloy.

Results of computer simulations of diffusion and relaxation in the liquid and the glassy state are presented for model systems and Cu33Zr67 and Se. The diffusion constant and the intermediate self scattering function show the typical behavior upon quenching from the liquid to the glass. The diffusion constant in the undercooled liquid can be fitted both with a Vogel-Fulcher or a mode coupling law. However, its pressure derivative, the activation volume, clearly follows the prediction of the mode coupling theory. From the diffusional isotope effect in the liquid we conclude that collectivity increases upon quenching to the glass transition. Checking the relaxations in the glass we find collective hopping of chains of atoms as elementary process. Both in the glassy state and in the undercooled liquid we observe an increase oc ∝√ι ofthe non-Gaussianity of the self correlation function, which measures the dynamic heterogeneity. This can be understood from the collective jump mechanism.

We applied the locally self-consistent multiple scattering (LSMS) method to the study Fe-based bulk amorphous metals. The LSMS method is an order-N approach to the electronic structure calculation for solid state materials based on density functional theory and local density approximation. Using LSMS method, we performed electronic structure calculations for the supercell samples generated by ab-initio molecular dynamics simulation. The equilibrium atomic volume and the bulk modulus are calculated based on the energy versus volume curve. The magnetic moment distribution in the samples is determined for both collinear and noncollinear cases. A comparison with the experimental results is also made.

The great number of different local environments in amorphous alloys leads to the evolution of complicated non collinear magnetic structures. Alloy additions can affect the magnetic structure in surprising ways. For example, replacement of a small amount of Fe with Co increases the saturation magnetization even though Co has a much smaller moment than Fe. The calculated behavior of the magnetic structure of (Fe(1-x)Mx) 0.8B0.2 with M=Co, Cr, Zr, and Mn2Zr are presented.

Alloys of composition (Hfx,Zr1-x)57Ti5Cu20Ni8Al10 and (Hfx,Zr1-x)52.5Ti5Cu17.9Ni14.6Al10, where x = 0, 0.2, 0.4. 0.6, 0.8, and 1.0, were evaluated for glass-forming ability, and the devitrification behavior on heating of the (Hfx,Zr1-x)52.5Ti5Cu17.9Ni14.6Al10 glasses was examined. Glass-forming ability was determined by suction casting 3-mm-diameter rods, followed by neutron diffraction examination. Results show that substitution of Hf for Zr in these alloys degrades glass-forming ability, and that this effect is more pronounced in compositions of the (Hfx,Zr1-x)57Ti5Cu20Ni8Al10 type. To examine devitrification behavior, thermal analysis was used to identify temperatures at which exothermic events occurred on heating in the (Hfx,Zr1-x)52.5Ti5Cu17.9Ni14.6Al10 series. The amorphous alloys were then subjected to annealing treatments corresponding to the exothermic events. Crystal structures formed during annealing were probedby neutron diffraction, and the size scale of features developed examined by small-angle neutron scattering. Results show that the initial decomposition produces a structure witha characteristic length scale, but it is not yet possible to comment on the mechanism.

The elastic properties of Pd39Ni10Cu10P21 bulk metallic glass (BMG) have been analysed using measurements of sound velocities. Different states of the Pd39Ni10Cu10P21 system (glassy state, supercooled liquid (SCL) and polycrystalline state) were obtained by annealing the samples near the glass transition and crystallization onset temperature. The microacoustical technique has been applied to measure local values of longitudinal and transverse elastic wave velocities and their distribution over a specimen. Finally sound velocities VL and VT, density ρ, bulk K and shear G elastic moduli were measured for different states. The values of ρ, VL and K decrease as temperature increases and the transition from glass to SCL takes place. In the crystalline state ultrasonic measurements were performed by the standard pulse ultrasonic technique with low-frequency flat transducer because of high ultrasonic attenuation in this state. Acoustic images (C-scans) demonstrate coarse-grained microstructure in this state. This is assumed to be characteristic of the microstructure obtained by crystallizing BMG.

Glass forming liquids exhibit their strong or fragile behaviour as a function of temperature, featuring a smaller or greater deviation from a simple Arrhenius law. The size of such deviation on a typical time scale of 10-6 s characterizes the ‘kinetic fragility’ F1/2 of a given material. Ultrasonic experiments in the MHz region are then suitable to show how the relaxational properties are influenced by the ‘fragile’ character of the liquid investigated. On this basis, measurements of acoustic attenuation at fixed frequency (15 MHz) have been performed on glass forming liquid ethylbenzene in the temperature range 100 K-300 K and compared with previous results on simple supercooled liquids derived from benzene. To prevent crystallization each temperature point below 190 K was reached by cooling the sample directly from 300 K and using also different cooling rates. Measurements have given evidence of a mechanical relaxation process: below the melting temperature the acoustic attenuation exhibits a peak and correspondingly the sound velocity increases from liquid-like to solid-like values. A stretched response function is required to reproduce the observed behaviour. The values of the Kohlrausch-Williams-Watts stretching parameter βkww which describe the experimental data are very low, if compared to those obtained for other glass-forming liquids.

Vickers micro-hardness indentations have been performed on a number of amorphous metals. The effects of changes in indentation load on the hardness and appearance of indents will be discussed for amorphous Al87Ni7Gd6. In addition, the effects of changes in test temperature on the micro-hardness and appearance of indentations in Vitreloy I are presented. A transition in deformation/flow character was detected with increasing test temperature for the Vitreloy I specimens. In addition, preliminary hardness data obtained at room temperature on an iron based metallic glass exhibited values in excess of 12 GPa without cracking.