Through high-energy x-ray diffraction and atomic pair density function analysis we find that Zr-based metallic alloy, heated to the supercooled liquid state under hydrostatic pressure and then quenched to room temperature, exhibits a distinct glassy structure. The PDF indicates that the Zr-Zr distances in this glass are significantly reduced compared to those quenched without pressure. Annealing at the glass transition temperature at ambient pressure reverses structural changes and the initial glassy state is recovered. This result suggests that pressure causes a liquid-to-liquid phase transition in this metallic alloy supercooled melt. Such a pressure induced transition is known for covalent liquids, but has not been observed for metallic liquids. The High Pressure Quenched glasses are stable in ambient conditions after decompression.

Even though the viscosity is one of the most fundamental properties of liquids, the connection with the atomic structure of the liquid has proven elusive. By combining inelastic neutron scattering with the electrostatic levitation technique the time-dependent pair-distribution function (i.e. the Van Hove function) has been determined for liquid Zr 80 Pt 20 . We show that the decay-time of the first peak of the Van Hove function is directly related to the Maxwell relaxation time of the liquid, which is proportional to the shear viscosity. This result demonstrates that the local dynamics for increasing or decreasing the coordination number of local clusters by one determines the viscosity at high temperature, supporting earlier predictions from molecular dynamics simulations.

Using high energy X-ray diffraction, we study the phase transition from α to ω in Zr via high-pressure torsion. We examine the evolution of the texture and establish the crystallographic orientation relationship between the α and ω phases. The orientation relationship supports the Silcock/Rabinkim direct transformation pathway and excludes the possibility of transition through the intermediate β phase, the Usikov/Zilbershtein pathway. The texture development in both α and ω phases of Zr during high-pressure torsion is quantified and explained in terms of the dominant slip system and the orientation relationship during martensitic transformation.

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