Some predictions concerning the configurational characteristics of the vandium - cobalt sigma phase

A simple pair-wise interaction energy model has been used to examine the possible configurational characteristics of σ(V - Co) as a function of composition and temperature. Near-maximum order, essentially of classic sigma-phase form, with preferential occupation of sublattices I and IV by cobalt and II by vanadium, is predicted for all compositions at room temperature. The calculations indicate significant disordering on heating, with most rapid changes in the approximate temperature range 800 - 1000 K, but with some order remaining up to the melting point. The model results are compared with published experimental indications of transformation in this phase. (Author)