Impact of Sulfur on the melt dynamics of glass forming Ti75Ni25−xSx

Abstract

Substitution of Nickel by Sulfur leads to bulk metallic glass formation in eutectic Ti75Ni25. In order to understand the improved glass forming ability, a detailed analysis of the melt dynamics was performed. We measured the density, the viscosity, and the self-diffusion of Ti75Ni25−xSx (x = 0, 5, 8) melts as a function of temperature. Moreover, the viscosity was measured under reduced gravity conditions to benchmark ground-based data. The self-diffusion coefficients were probed by incoherent, quasi-elastic neutron scattering. All measurements were combined with electrostatic or electromagnetic levitation, in order to process these highly reactive Titanium-based melts. From the measured density, the packing fraction was calculated as a function of temperature. In contrast to other bulk metallic glasses, the decrease in melt dynamics comes along with the decrease in packing density.