Relations between Structure, Phase Formation and Phase Transitions in Supercooled Metallic Liquids and Glasses

Kenneth F. Kelton, Washington University, DMR 0856199

Metallic glasses have an amorphous structure that is inherited from the liquid. The nature of the liquid structure, how it changes with temperature, and how it is related to glass formation and glass structure are poorly understood. Correlating structural and physical property measurements obtained from a wide-range of glass-forming liquids using an electrostatic levitation facility (ESL) constructed at Washington University, we are gaining new insight into these questions.

1. We have shown that the thermal expansivity, , in Cu-Zr liquids is largest for the best glass-forming compositions. The larger at high temperatures indicates a decreased liquid fragility.

2. In all of the liquids we have studied (in excess of 100) the location of the first peak in S(q) at q1 is proportional to v-1/3, where v is the specific volume of the liquid. This suggests a faster method for obtaining

3. The slope of a plot of 1/q1 as a function of temperature (see figure) is proportional to . is greater in the Ni62Nb38 liquid (the better glass former) than in Ni59.5Nb40.5 (a eutectic liquid), in agreement with the observation in Cu-Zr liquids.

4. The liquid data do not extrapolate to those of the glass at the glass transition temperature, Tg, indicating that structural change accelerates near Tg, a behavior characteristic of more fragile liquids.

Broader Impacts of the Relations between Structure, Phase Formation and Phase Transitions in Supercooled Metallic Liquids and Glasses

Kenneth F. Kelton, Washington University, DMR 0856199

Education - Graduate and undergraduate students actively participate in this research, using novel equipment and learning and helping to develop new techniques.

Practical Applications - Metallic glasses are some of the most intensely studied modern materials. The list of applications is rapidly growing as new metallic glasses are discovered. The results from this research are pointing the way to gain a deeper understanding of the role of liquid structure in glass formation and are providing new approaches to identify promising alloy systems for glass formation.

Left – Undergraduate Corrie Miller preparing the arc-melting facility for sample preparation.

Top Right – Graduate student Matt Blodgett (sitting) explaining to undergraduate Zack Markow how to use the electrostatic levitation facility.

Bottom Right – Graduate student, Chris Pueblo making differential scanning calorimetry measurements of metallic glasses to determine their fragility index.