Cracking the formation of metallic glasses

Metallic glasses are useful materials for extreme environments due to their high hardness, strong elasticity, and excellent corrosion resistance. They are produced by making alloys of metals like zirconium, titanium, and iron at high temperatures, then rapidly cooling the substance so that its atoms solidify in a messy glass structure rather than an ordered crystalline one. But details at the atomic level of the glass-forming process are not well understood, limiting how the materials can be synthesized and applied.

Dong et al. studied a key step of metallic glass synthesis, the liquid-to-liquid phase transition (LLPT), to assess how it influenced the glass-forming ability of materials. They found that good glass formers had a more pronounced LLPT compared to average glass formers.

“For materials science, there is a long-standing problem of why some liquids can easily form glass and other liquids cannot,” said author Zhenduo Wu.

To find out, the team aimed to directly probe the structural change from the high-temperature liquid to the glass state.

They used a custom furnace to melt together different formulas of zirconium, copper, and aluminum at more than 1300 degrees Kelvin. Then they rapidly cooled the materials to measure their structural evolution, density changes, and phase transitions using X-ray diffraction and electrostatic techniques. Zr₄₆Cu₄₆Al₈, with a strong LLPT characterized by a higher entropy post-transition structure, was a better glass former than Zr₅₆Cu₃₆Al₈.

Now that they know LLPT is important in metallic glasses’ structural formation, the authors plan to use this knowledge to design better performing materials.

“I think we can tune the structure of metallic glasses to figure out how we can get excellent mechanical properties,” said author Weixia Dong.

Source: “Evidence of liquid-liquid phase transition in Zr-Cu-Al melts and its link to glass-forming ability,” by Weixia Dong, Sinan Liu, Zhenduo Wu, Jiale Ma, Yang Ren, Xun-Li Wang, and Si Lan, Applied Physics Letters (2025). The article can be accessed at https://doi.org/10.1063/5.0299273 .