GTBL042-11 GTBL042-Callister-v3 October 4, 2007 11:59
2nd Revised PagesQuestions and Problems • 457Time (s)Temperature (°C)0.1 10AA
PAFM103 105 10702004006008001000 Figure 11.50 Continuous cooling transformation
diagram for a 0.35 wt% C iron–carbon alloy.11.19Rank the following iron–carbon alloys and
associated microstructures from the hardest
to the softest:(a)0.25 wt% C with coarse
pearlite,(b)0.80 wt% C with spheroidite,(c)
0.25 wt% C with spheroidite, and(d)0.80
wt% C with fine pearlite. Justify this rank-
ing.
11.20Briefly describe the simplest heat treatment
procedure that would be used in converting
a 0.76 wt% C steel from one microstructure
to the other, as follows:
(a)Spheroidite to martensite
(b)Pearlite to bainite
(c)Pearlite to spheroidite
(d)Bainite to spheroidite
11.21Estimate the Rockwell hardnesses for spec-
imens of an iron–carbon alloy of eutectoid
composition that have been subjected to the
heat treatments described in parts (b) and (c)
of Problem 11.10.
11.22Estimate the Brinell hardnesses for speci-
mens of a 1.13 wt% C iron–carbon alloy that
have been subjected to the heat treatments
described in parts (b) and (d) of Problem
11.11.11.23For a eutectoid steel, describe isothermal
heat treatments that would be required to
yield specimens having the following Brinell
hardnesses:
(a)180 HB,
(b)220 HB,
(c)500 HB.Crystallization (Polymers)
11.24Determine values for the constantsnand
k(Equation 11.17) for the crystallization of
polypropylene (Figure 11.46) at 150◦C.Melting and Glass Transition Temperatures
11.25Of those polymers listed in Table 11.3, which
polymer(s) would be best suited for use as ice
cube trays? Why?Factors That Influence Melting and
Glass Transition Temperatures
11.26For each of the following pairs of polymers,
do the following: (1) state whether or not it
is possible to determine whether one poly-
mer has a higher melting temperature than
the other; (2) if it is possible, note which has