GTBL042-10 GTBL042-Callister-v2 August 13, 2007 18:16
10.16 Ceramic Phase Diagrams • 373composition. Examples of congruent transformations include allotropic transforma-
tions (Section 3.10) and melting of pure materials. Eutectic and eutectoid reactions,
as well as the melting of an alloy that belongs to an isomorphous system, all represent
incongruent transformations.
Intermediate phases are sometimes classified on the basis of whether they melt
congruently or incongruently. The intermetallic compound Mg 2 Pb melts congruently
at the point designatedMon the magnesium–lead phase diagram, Figure 10.20. Also,
for the nickel–titanium system, Figure 10.22, there is a congruent melting point for
theγsolid solution that corresponds to the point of tangency for the pairs of liquidus
and solidus lines, at 1310◦C and 44.9 wt% Ti. Furthermore, the peritectic reaction is
an example of incongruent melting for an intermediate phase.Concept Check 10.6The figure below is the hafnium–vanadium phase diagram, for which only single-
phase regions are labeled. Specify temperature–composition points at which all eu-
tectics, eutectoids, peritectics, and congruent phase transformations occur. Also, for
each, write the reaction upon cooling. [Phase diagram fromASM Handbook,Vol. 3,
Alloy Phase Diagrams,H. Baker (Editor), 1992, p. 2.244. Reprinted by permission
of ASM International, Materials Park, OH.]2200200018001600140012001000Hf
LHfV 2VHf0 2 0406080100
(Hf) Composition (wt % V) (V)Temperature (°C)[The answer may be found at http://www.wiley.com/college/callister (Student Companion Site).]10.16 CERAMIC PHASE DIAGRAMS
It need not be assumed that phase diagrams exist only for metal–metal systems; in
fact, phase diagrams that are very useful in the design and processing of ceramic
systems have been experimentally determined for quite a number of these mate-
rials. For binary or two-component phase diagrams, it is frequently the case that