Kinetics and thermodynamics of thermally induced structural transformations of amorphous Fe _(75)Ni _2Si _8B _(13)C _2 alloy

摘要

Thermally induced structural transformations of amorphous Fe _(75)Ni _2Si_ 8B _(13)C _2 alloy have been characterized in terms of both thermodynamic and kinetic parameters of individual processes. The crystallization of the alloy occurs in temperature region around 500°C with primary crystallization of stable α-Fe(Si) and Fe 2B and metastable Fe 3B phase, followed by transformation of Fe 3B to Fe 2B. The latter process exhibits the lowest values of apparent activation energy and change in Gibbs free energy of activated complex, as well as negative value of change in entropy of activated complex, indicating that this corresponds to transformation of one crystalline phase to another, making it the least complex of the four processes. Another set of transformations occurs around 700°C, where two consecutive processes are observed: phase transformation of α-Fe(Si) to α _1-Fe(Si) and subsequent transformation of a portion of α _1-Fe(Si) to Fe _2B. The consecutive nature of these processes is indicated by the fact that the first process exhibits significantly higher values of apparent activation energy and changes in Gibbs free energy and entropy of activated complex.