Quantifying the origin of metallic glass formation #MMPMID26786966
Johnson WL; Na JH; Demetriou MD
Nat Commun 2016[]; 7 (ä): ä PMID26786966show ga
The waiting time to form a crystal in a unit volume of homogeneous undercooled liquid exhibits a pronounced minimum ?X* at a ?nose temperature' T* located between the glass transition temperature Tg, and the crystal melting temperature, TL. Turnbull argued that ?X* should increase rapidly with the dimensionless ratio trg=Tg/TL. Angell introduced a dimensionless ?fragility parameter', m, to characterize the fall of atomic mobility with temperature above Tg. Both trg and m are widely thought to play a significant role in determining ?X*. Here we survey and assess reported data for TL, Tg, trg, m and ?X* for a broad range of metallic glasses with widely varying ?X*. By analysing this database, we derive a simple empirical expression for ?X*(trg, m) that depends exponentially on trg and m, and two fitting parameters. A statistical analysis shows that knowledge of trg and m alone is therefore sufficient to predict ?X* within estimated experimental errors. Surprisingly, the liquid/crystal interfacial free energy does not appear in this expression for ?X*.
free
free
free
Nat+Commun 2016 ; 7 (ä): ä
