Open AccessMultistep Crystallization and Melting Pathways in the Free‐Energy Landscape of a Au–Si Eutectic Alloy
Author(s) -
Kurtuldu Güven,
Löffler Jörg F.
Publication year - 2020
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.201903544
Subject(s) - eutectic system , nucleation , materials science , metastability , crystallization , differential scanning calorimetry , melting point , alloy , phase diagram , thermodynamics , enthalpy of fusion , melting point depression , phase (matter) , enthalpy , chemical physics , crystallography , metallurgy , chemistry , composite material , physics , organic chemistry
Crystals do eventually melt if they are heated to their characteristic melting point. However, this is practically only the case for high‐temperature stable crystals, whereas low‐temperature metastable crystals generally transform, before melting, into a more stable solid during heating. Here, it is illustrated that low‐temperature crystals can, however, be melted via fast differential scanning calorimetry (FDSC), even in metallic systems where nucleation and growth kinetics are rapid. For a Au–Si eutectic alloy, various metastable and stable solid states, i.e., (Au–α), (Au–β), γ, and (Au–Si), which form under well‐controlled conditions and melt at high heating rates by preventing the metastable‐to‐stable solid phase transition, are isolated. It is demonstrated that Au 81.4 Si 18.6 can fully melt at various temperatures, i.e., 294 °C, 312 °C, 352 °C, and 363 °C, with differing melting enthalpies ranging from 6.52 to 9.83 kJ mol −1 . The melting and crystallization paths of the metastable solids are determined by constructing an energy−temperature diagram. This approach advances the general understanding of nucleation in metallic and other systems, and is expected to contribute to the detailed understanding of thermophysical phenomena that occur at spatially reduced dimensions and/or short time scales, for example in thin‐film deposition, nanomaterials production, or additive manufacturing.