Bulk metallic glass formation from strong liquids

The kinetics and thermodynamics of supercooled bulk metallic glass forming liquids are studied by measuring the viscosity and the thermodynamic functions depending on temperature. Viscosity measurements are performed from the melting point down to the glass transition region. These investigations reveal that bulk metallic glass formers are "strong" liquids with a high melt viscosity that is three orders of of magnitude larger than in pure metals and most alloys. A thermodynamic analysis shows that these materials exibit small entropies of fusion yielding small driving forces far crystallization upon undercooling. Both, the sluggish kinetics and the favorable thermodynamics in these alloys lead to much smaller nucleation rates for crystallization compared to previous alloys that were more "fragile". The microscopic origin for the kinetic and thermodynamic behavior is a strong tendency to develop short range order in the liquid state.