Entropy and free energy at the hcp-bcc transformation temperature in metals and alloys.

It has been shown that a plot of the Φ function, defined by - ( G - G)/T where G and G are respectively the Gibb's free energies at the hcp → bcc allotropie transformation temperature (T ) and at absolute zero, vs the entropy (S) of the hcp phase at T is linear. This concept of the Φ function and its relation to S can be extended to alloys with the aid of the 'central atoms' solution model. Its use has been demonstrated with respect to the Ti-Zr system where the estimated transformation temperatures are shown to be within the (hcp + bcc) phase field. [ABSTRACT FROM AUTHOR]