Ternary restricted-equilibrium phase diagrams—I. A first report: General principles and definitions

Abstract

The amounts of phases and microstructural constituents present in a ternary alloy after casting and solidification at some finite cooling rate will generally be different from those predicted by the equilibrium diagram. Deviations are particularly relevant in the composition range where a homogeneous solid solution of the two solute elements in the base metal exists under equilibrium conditions while actual solidification proceeds by precipitation of a binary eutectic mixture or a ternary eutectic, or both. After the solidification path of a large number of compositions in this range is assessed (e.g. by numerical simulation), the information on the phases and microstructural constituents can be graphically represented as a function of temperature and concentration. The principal features of the resulting diagrams (restricted-equilibrium phase diagram and restricted-equilibrium microstructure diagram) are discussed in the first part while a practical application is shown in the second part of this work.