THERMODYNAMIC ACTIVITIES OF ALLOYS

The concept of activity is discussed briefly. Emphasis is placed on th e principles of activity measurement and recent experimental developme nts as well as on temperature and concentration dependences, thermodyn amic modeling, and modern thermodynamic evaluation. The activities as well as mixing properties of all types of alloys, even including metal lic melts showing short-range ordering, can be represented algebraical ly by means of a simple concept. Using just one common set of paramete rs allows a straightforward description of combined temperature and co ncentration dependences. An extended temperature dependence of the exc ess Gibbs energy, as necessary for this purpose, has been derived. The presented concept makes possible putting together all activity measur ements of a multicomponent alloy system for performing one algebraic o verall best-fit. In connection with a personal computer this forms a v ery convenient, interactive evaluation tool yielding a considerable re duction of both, the experimental work and the time spent on evaluatio n. (C) 1998 Elsevier Science B.V.