Callister - An introduction - 8th edition

384 • Chapter 10 / Phase Transformations
10.13
r* 2 SL
¢G y
Critical radius for stable solid particle
(heterogeneous nucleation)
351
10.14
¢G* a 16p3 SL
b S1u2
3¢G 2 y
Activation free energy for formation of stable
solid particle (heterogeneous nucleation)
351
10.17 y 1exp 1kt n 2
Fraction of transformation (Avrami equation) 355
10.18 rate 1
Transformation rate 355
t 0.5
List of Symbols
Symbol
Meaning
Volume free energy
¢H f
Latent heat of fusion
k, n Time-independent constants
S( u) Nucleus shape function
T
Temperature (K)
T m
Equilibrium solidification temperature (K)
t 0.5 Time required for a transformation to proceed to 50%
completion
Surface free energy
IL Liquid-surface interfacial energy (Figure 10.5)
SL
Solid-liquid interfacial energy
SI
Solid-surface interfacial energy
u
Wetting angle (angle between SI and SL vectors) (Figure 10.5)
¢G y
Furthermore, reference to the heat treating of steels (as discussed in Chapter
Processing/Structure/Properties/Performance Summary
For iron–carbon alloys, in addition to discussions of the heat treatments that produce
the several microconstituents (fine/coarse pearlite, bainite, martensite, etc.)
and the mechanical properties of same, correlations were made between mechanical
properties and structural elements of these microconstituents.These correlations
are indicated in the following diagram.
Steel Alloys
(Structure)
Development of
microstructure in
iron–iron carbon
alloys
(Chapters 9 & 10)
Mechanical properties
of iron–iron carbide
alloys
(Chapter 10)
Steel Alloys
(Properties)
Pearlite (coarse and fine)
Bainite
Spheroidite
Martensite
Tempered martensite
11) normally means tempering of martensite to form tempered martensite. An
understanding of the conditions under which martensite forms is facilitated by
utilizing continuous cooling and isothermal transformation diagrams (Sections 10.5
and 10.6). In addition, these diagrams are just extensions of the iron–iron carbide
phase diagram (Section 9.18). The following diagram notes these relationships.