Selection and Editing of Diagrams and Crystal Data
Although this resource includes diagrams critically evaluated under the international
program coordinated by the Alloy Phase Diagram International Commission (APDIC), the
vast majority of diagrams contained herein are not from the APDIC Program. The unevaluated
data from the literature, however, are not merely reproduced as presented in the source.
An element of judgment as to the value of the original publications was incorporated
into the final drawings and the data captured for each. Obvious errors in construction
by the original authors were corrected, if possible. Significant issues are noted in
the "Remarks" presented with each diagram.
Crystallographic data are included for the chemical elements and binary and ternary
phases. These data were critically evaluated, and for each phase, only the best data set
In addition to correction of errors, the presentation of the diagrams and associated data
have been standardized as described below.
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Naming of Diagrams
Diagrams names are constructed from the binary or ternary element system in which the
diagram appears, the year the source was published, and the last name and initials of
the first author listed in the source. For example, "Pb-Sn Phase Diagram
(1990 Karakaya I.)" is a binary diagram in the lead (Pb) and tin (Sn) system for which
the source document was published in 1990 by I. Karakaya and W.T. Thompson.
Elements are presented in alphabetical order by element designation. For example, all
"iron-carbon" phase diagrams are presented as "C-Fe" diagrams. However, on the
Explore tree, diagrams can be found by expanding any of the elements included;
for example, all C-Fe diagrams can be found by expanding either C (Carbon) or Fe (Iron).
Diagram names are not necessarily unique because the authors may have published multiple
diagrams with different composition ranges or temperature ranges in the same source or
in different sources published in the same year. A "Unique ID No." has been assigned to
each diagram to help differentiate among diagrams that may have the same name.
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Arrangement of Diagrams
Binary diagrams are presented in alphabetical order by element designation. For example,
an Al-Ni diagram is presented with Al at the bottom left and Ni at the bottom right of
the horizontal axis. The axis plots the composition of nickel. If the diagram presents
the full composition range of the system, then the bottom left would represent 100 at.%
Al and the bottom right 100 at.% Ni.
For triangular ternary diagrams (such as liquidus projections and isothermal sections),
component A is placed at the bottom left, B at the top, and C at the bottom right
(where component A is the element that comes first in alphabetical order, B second, and
C third). Additional information is provided in the section "Ternary Diagrams"
of the article "Introduction to Phase Diagrams," which can be accessed under
the Help tab.
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Unique Phase Label System
In place of the usual Greek letter designations, phases are identified according to a unique phase
label system that is consistent across all diagrams.
Terminal solid solutions are shown as the element in parentheses. Example: (Al)
For elements with an allotropic transformation, the room temperature allotrope is designated with "rt"
after the terminal solid solution name. The allotrope that is stable in the next highest temperature range
is designated "ht 1," the allotrope that is stable in the next highest temperature range is designated
"ht 2," and so on. When there is only one allotropic transformation, only "rt" and "ht" are used.
Examples: (Pu) rt, (Pu) ht 1, (Pu) ht 2, and so on.
In ternary diagrams, terminal solid solutions and intermediate phases involving an element that undergoes
an allotropic transformation show the allotrope that is present adjacent to the element. Examples: (Ti ht, Cr),
(Ag, Co ht, Pd), (Ag0.5 Cd0.5 ht1, Ag0.67 Al0.33),
and (AgCd rt, AuCd ht)
Intermediate phases are identified by their general composition, noted by whole number or decimal subscripts to the
elemental components. In cases where these phases have different high temperature and low temperature
structures, the "rt" and "ht" designations are used. Examples: Au4Al ht, Ag3CuS2 rt, Ag9GaTe6 ht,
and MgAg0.20Zn1.80 21R
Additional information is provided in the article "How to Interpret and Understand Villars Distinct Phase
Labels," which can be accessed under the Help tab.