State Of Bulk Metallic Glass Research Articles

The effects of high magnetic field on crystallization of Fe71(Nb0.8Zr0.2)6B23 bulk metallic glass

We report that the high magnetic field (HMF) retards crystallization, i.e. helps to keep a fully amorphous state of bulk metallic glass (BMG) upon isothermal annealing in the supercooled liquid region. Particularly, the application of HMF during an annealing process can effectively suppress the crystallization of boride (e.g. Fe23B6-type phase, or even a hard magnetic Fe2B phase) from the amorphous matrix of Fe71(Nb0.8Zr0.2)6B23 BMG. Thus by delaying crystallization, HMF can enhance the soft magnetic properties of high B content Fe-based bulk amorphous and nanocrystalline materials.

Elastic Constants, Equation of State and Mechanical Relaxations of some Metallic Glasses at High Pressure

One of the fundamental physical quantities necessary to describe the mechanical properties of the materials is the bulk modulus. In the present report, a simple method to estimate the values of the bulk modulus and its pressure derivative of metallic glasses is presented. The method which is based on a jellium model of metals provides a good agreement with measured data. The estimated values of the elastic constants have been used to determine the equation of state of bulk metallic glasses. It is found that the usual Murnaghan equation of state deviates considerably from the experimental results at high pressures. The deviation has been interpreted to arise from the structural relaxations. The effect of pressure on the fragility of bulk metallic glasses is discussed briefly.

Equation of state of bulk metallic glasses studied by an ultrasonic method

The acoustic velocities and their pressure dependence of various Zr- and Pd-based bulk metallic glasses (BMGs) have been measured by using a pulse echo overlap method. The elastic constants as well as their pressure dependence of the BMGs have been determined, and the equation of state of these BMGs was obtained and compared to that of other glasses and crystalline solids. The structural characteristic of the BMGs is discussed.

Isotope effect of diffusion in the supercooled liquid state of bulk metallic glasses

The isotope effect, E=(Dα/Dβ−1)/(mβ/mα−1), of cobalt diffusion in the deeply supercooled liquid state of the bulk metallic glass formers Zr46.7Ti8.3Cu7.5Ni10Be27.5 and Zr65Cu17.5Ni10Al7.5 has been measured employing the radiotracers 57Co and 60Co in conjunction with serial sectioning by means of ion-beam depth profiling. In both alloys a small mass dependence with E≈0.10 is observed. This dependence has no temperature dependence in a range of 120 K in the supercooled liquid state encompassing four orders of magnitude in the diffusivity. We suggest that these results show that long-range diffusion in a deeply supercooled liquid is not mediated by viscous flow but proceeds by collective hopping processes involving about 10 atoms.