APPLICATION OF STATISTICAL MECHANICS TO SOLID SOLUTIONS OF INTERSTITIAL IMPURITIES IN BINARY ALLOYS

摘要

A statistical mechanical model has been developed for ternary interstitial alloys in the frame- work of the canonical ensemble. Short-range repulsive interactions among interstitials have been taken into account assuming a hard-sphere pair interaction potential. Sites of different geometrical kind (octahedral, tetrahedral, etc.) have been considered and further distinguished on the basis of either the chemical compo- sition of their first shell of neighbouring metal atoms or of the distribution of the two metallic species within this shell. Analytical expressions for the thermodynamic functions of the system and for the occu- pancy probabilities of the different interstitial sites have been derived for a given alloy and assigned site energies. A general procedure for the evaluation of the blocking factors and the interstitial jump probabil- ities is proposed and applied to random f.c.c. and b.c.c. binary alloys containing H. The results are dis- cussed in relation to diffusivity and anelastic relaxations associated with the interstitial impurity.