Fundamentals of Materials Science and Engineering: An Integrated Approach, 3e

GTBL042-11 GTBL042-Callister-v3 October 4, 2007 11:59

2nd Revised Pages

452 • Chapter 11 / Phase Transformations

Concept Check 11.9

For each of the following two polymers, plot and label a schematic specific volume-

versus-temperature curve (include both curves on the same graph):

• Spherulitic polypropylene, of 25% crystallinity, and having a weight-average
  molecular weight of 75,000 g/mol


• Spherulitic polystyrene, of 25% crystallinity, and having a weight-average molec-
  ular weight of 100,000 g/mol.

[The answer may be found at http://www.wiley.com/college/callister (Student Companion Site).]

Concept Check 11.10

For the two polymers described below, do the following: (1) state whether or not it is

possible to determine whether one polymer has a higher melting temperature than

the other; (2) if it is possible, note which has the higher melting temperature and

then cite reason(s) for your choice; and (3) if it is not possible to decide, then state

why not.

• Isotactic polystyrene that has a density of 1.12 g/cm^3 and a weight-average molec-
  ular weight of 150,000 g/mol


• Syndiotactic polystyrene that has a density of 1.10 g/cm^3 and a weight-average
  molecular weight of 125,000 g/mol.

[The answer may be found at http://www.wiley.com/college/callister (Student Companion Site).]

SUMMARY

Basic Concepts

The Kinetics of Phase Transformations

The first set of discussion topics for this chapter included phase transformations in

metals—modifications in the phase structure or microstructure—and how they affect

mechanical properties. Nucleation and growth processes, which are involved in the

production of a new phase, were discussed, in addition to the temperature depen-

dence of phase transformation rate. Other kinetic principles were treated, including,

for solid-state transformations, the dependence of fraction of transformation on time.

Metastable Versus Equilibrium States

Isothermal Transformation Diagrams

Continuous Cooling Transformation Diagrams

Mechanical Behavior of Iron–Carbon Alloys

Tempered Martensite

As a practical matter, phase diagrams are severely restricted relative to transforma-

tions in multiphase alloys, because they provide no information on phase transfor-

mation rates. The element of time is incorporated into both isothermal transforma-

tion and continuous cooling transformation diagrams; transformation progress as a