Phase constitution of some intermetallics in continuous quaternary pillar phase diagrams

In order to express multicomponent phase relationships, a new type of phase diagram, named a “pillar phase diagram,” is proposed. The pillar phase diagram is a sort of quaternary and Brewertype phase diagram. A pillar phase diagram at a temperature is easily constructed by (1) composing three sides of Brewer-type ternary-phase diagrams along the periodic table and (2) piling triangles of general ternary phase diagrams along the periodic table. Using the pillar phase diagrams, systematic understandings of phase constitution and stability along the periodic table can be performed for (1) binary intermetallics containing ternary and quaternary additional elements and (2) ternary intermetallics containing quaternary elements. Thus, the diagrams are convenient in terms of alloy design of multiphase intermetallic alloys. In this paper, the concept and the construction method of the pillar phase diagrams are described, and some examples are shown for systems related with L1₂ Ni₃Al, B2 NiAl, L2₁ Ni₂AlTi, B2 NiTi, B2 FeTi, L1₀ TiAl, and L1₂ Al₃Ti alloys.