Despite its importance, a thermodynamic approach to determining the glass-forming ability (GFA) of bulk metallic glass (BMG) remains a goal to be achieved. We examined the GFA of water-quenched Pd-P-based and Pt 60Ni15P25 BMG's in which their molten alloys were sufficiently treated with a dehydrated B2O3 flux prior to and during quenching to room temperature. This allowed us to envisage the applicability of the classical steady-state homogeneous nucleation theory because the suppression of heterogeneous nucleation worked effectively. GFA was examined by comparing the critical cooling rate Rch for glass formation with the maximum diameter dmax of glass. To calculate Rch, the homogeneous nucleation rate Iss(T), and the growth rate uc(T) were estimated as functions of the undercooling temperature of molten alloys. Then, the free energy difference ΔGL-x(T) between the liquid and crystalline phases, and the viscosity η(T) of the liquid were experimentally determined while the surface energy σsL(T) at the liquid-nucleus interface was estimated by calculation. The dmax of rod BMG's correlated strongly to Rch through the relation Rch dmax-3/10 mm3 Ks-1.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2011 Feb 11|