10 research outputs found
Relation of the thermodynamic parameter of disordering with the width of structure factor and defect concentration in a metallic glass
In this work, we show that above the glass transition there exists a strong
unique interrelationship between the thermodynamic parameter of disorder of a
metallic glass derived using its excess entropy, diffraction measure of
disorder given by the width of the X-ray structure factor and defect
concentration derived from shear modulus measurements. Below the glass
transition, this relationship is more complicated and depends on both
temperature and thermal prehistory.Comment: 6 pages, 2 Figure
Critical behavior of the fluctuation heat capacity near the glass transition of metallic glasses
The high-frequency shear modulus of five Zr-, Pd-, Cu-based conventional and
two high-entropy bulk metallic glasses was measured in a wide temperature range
up to the beginning of crystallization. Using these data and general
thermodynamic relations, the "fluctuation" heat capacity
determined by local structural fluctuations in the defect regions is introduced
and calculated. It is found that temperature dependence for all
metallic glasses has a large peak located slightly below or above the glass
transition temperature but clearly lower than the crystallization onset
temperature. The form of this peak resembles the characteristic -peak
typical for order-disorder phase transitions. It is suggested that this -peak reflects certain underlying critical phenomenon. The critical
temperature (peak temperature) and corresponding critical index
are determined. Averaged over all seven metallic glasses under investigation in
the initial and relaxed states, the critical index . The results
obtained indicate that the fluctuations of thermal energy near the glass
transition bear the marks of a continuous phase transition. However, the
derived critical index is between those corresponding to a second-order phase
transition () and a critical transition characterized by a
tricritical point ().Comment: 18 pages, 4 figure