Callister - An introduction - 8th edition

336 • Chapter 9 / Phase Diagrams
Composition Solidus Liquidus
(wt% Si) Temperature ( C) Temperature ( C)
0 938 938
10 1005 1147
20 1065 1226
30 1123 1278
40 1178 1315
50 1232 1346
60 1282 1367
70 1326 1385
80 1359 1397
90 1390 1408
100 1414 1414
Interpretation of Phase Diagrams
9.8 Cite the phases that are present and the phase
compositions for the following alloys:
(a) 90 wt% Zn–10 wt% Cu at 400C (750F)
(b) 75 wt% Sn–25 wt% Pb at 175C (345F)
(c) 55 wt% Ag–45 wt% Cu at 900C (1650F)
(d) 30 wt% Pb–70 wt% Mg at 425C (795F)
(e) 2.12 kg Zn and 1.88 kg Cu at 500C (930F)
(f) 37 lb m Pb and 6.5 lb m Mg at 400C (750F)
(g) 8.2 mol Ni and 4.3 mol Cu at 1250C
(2280F)
(h) 4.5 mol Sn and 0.45 mol Pb at 200C
(390F)
9.9 Is it possible to have a copper–nickel alloy
that, at equilibrium, consists of a liquid phase
of composition 20 wt% Ni–80 wt% Cu and
also an phase of composition 37 wt% Ni–63
wt% Cu? If so, what will be the approximate
temperature of the alloy? If this is not possible,
explain why.
9.10 Is it possible to have a copper–zinc alloy that,
at equilibrium, consists of an phase of composition
80 wt% Zn–20 wt% Cu, and also a
liquid phase of composition 95 wt% Zn–5
wt% Cu? If so, what will be the approximate
temperature of the alloy? If this is not possible,
explain why.
9.11 A copper–nickel alloy of composition 70 wt%
Ni–30 wt% Cu is slowly heated from a temperature
of 1300C (2370F).
(a) At what temperature does the first liquid
phase form?
(b) What is the composition of this liquid
phase?
(c) At what temperature does complete melting
of the alloy occur?
(d) What is the composition of the last solid
remaining prior to complete melting?
9.12 A 50 wt% Pb–50 wt% Mg alloy is slowly
cooled from 700C (1290F) to 400C (750F).
(a) At what temperature does the first solid
phase form?
(b) What is the composition of this solid phase?
(c) At what temperature does the liquid
solidify?
(d) What is the composition of this last remaining
liquid phase?
9.13 For an alloy of composition 74 wt% Zn–26
wt% Cu, cite the phases present and their
compositions at the following temperatures:
850C, 750C, 680C, 600C, and 500C.
9.14 Determine the relative amounts (in terms of
mass fractions) of the phases for the alloys
and temperatures given in Problem 9.8.
9.15 A 1.5-kg specimen of a 90 wt% Pb–10 wt%
Sn alloy is heated to 250C (480F); at this
temperature it is entirely an -phase solid
solution (Figure 9.8).The alloy is to be melted
to the extent that 50% of the specimen is
liquid, the remainder being the phase. This
may be accomplished either by heating the
alloy or changing its composition while holding
the temperature constant.
(a) To what temperature must the specimen
be heated?
(b) How much tin must be added to the 1.5-kg
specimen at 250C to achieve this state?
9.16 A magnesium–lead alloy of mass 5.5 kg consists
of a solid phase that has a composition
just slightly below the solubility limit at 200C
(390F).
(a) What mass of lead is in the alloy?
(b) If the alloy is heated to 350C (660F),
how much more lead may be dissolved in the
phase without exceeding the solubility limit
of this phase?
9.17 A 90 wt% Ag–10 wt% Cu alloy is heated to
a temperature within the liquid phase
region. If the composition of the liquid phase
is 85 wt% Ag, determine:
(a) The temperature of the alloy