GTBL042-10 GTBL042-Callister-v2 August 13, 2007 18:16
358 • Chapter 10 / Phase Diagrams(Pb) Composition (wt% Sn) (Sn)Composition (at% Sn)Temperature (°F)Temperature (°C)0 1000 20 40 60 80 100500400300200100600
30020010020 40 60 80+Liquid183 °C
18.3 61.9 97.8+ L+ L327 °C232 °C0Figure 10.8 The lead–tin phase diagram. [Adapted fromBinary Alloy Phase Diagrams,2nd
edition, Vol. 3, T. B. Massalski (Editor-in-Chief), 1990. Reprinted by permission of ASM
International, Materials Park, OH.]Another common eutectic system is that for lead and tin; the phase diagram
(Figure 10.8) has a general shape similar to that for copper–silver. For the lead–
tin system the solid solution phases are also designated byαandβ; in this case,α
represents a solid solution of tin in lead and, forβ, tin is the solvent and lead is the
solute. The eutectic invariant point is located at 61.9 wt% Sn and 183◦C (361◦F).
Of course, maximum solid solubility compositions as well as component melting
temperatures will be different for the copper–silver and lead–tin systems, as may be
observed by comparing their phase diagrams.
On occasion, low-melting-temperature alloys are prepared having near-eutectic
compositions. A familiar example is the 60–40 solder, containing 60 wt% Sn and
40 wt% Pb. Figure 10.8 indicates that an alloy of this composition is completely
molten at about 185◦C (365◦F), which makes this material especially attractive as a
low-temperature solder, since it is easily melted.Concept Check 10.4
At 700◦C (1290◦F), what is the maximum solubility(a)of Cu in Ag?(b)Of Ag in
Cu?[The answer may be found at http://www.wiley.com/college/callister (Student Companion Site).]