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

Abstract

It has been shown that a plot of the Φ function, defined by - (G tr - Go)/Ttr where Gtr and G o are respectively the Gibb's free energies at the hcp → bcc allotropie transformation temperature (T tr ) and at absolute zero, vs the entropy (Str) of the hcp phase at Ttr is linear. This concept of the Φ function and its relation to S tr 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. © 1980 American Society for Metals and The Metallurgical Society of AIME.