Use of thermodynamics and phase equilibria to predict the behavior of the rare earth elements in steel

Examination of the standard free energy of formation data for the various rare earth (RE) compounds makes it possible to make predictions about the reactions of rare earths with oxygen, sulfur, and white metals. Most results are compatible with the theoretical predictions, whereas other predictions appear to be erroneous, and finally some of the reactions that are observed can not be explained by examination of the standard free energies of formation alone. From the phase diagrams of some of the rare earths and the ''white metals'' which include lead, arsenic, etc. it is possible to predict that rare earths should be able to obviate the deleterious effect of some of these elements on the mechanical properties of steel. (U.S.)