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Matsc 503  Kinetics of Materials Processes
Sample Final Exam Questions
1.
Discuss the three regimes of grain boundary diffusion, A, B and C,
as classified by Harrison:
(a)
(10 points ) Give the conditions for each regime in terms of the spacing between grain
boundaries, grain boundary thickness, grain boundary diffusion coefficient, lattice
diffusion coefficient, diffusion time, etc.
.
(b) (10 points) Discuss the possibility of measuring the grain boundary diffusion coefficient
in each regime.
2.
A solidsolid transformation produces cubic precipitates.
The surface energies are
γ
coh
= 0.04
J m
2
for coherent precipitates and
γ
incoh
= 0.40 J m
2
for incoherent precipitates.
∆
G
v
=
2
×
10
8
∆
T
T
eq
Jm

3
,
T
eq
=
1000
K
and strain energy/unit volume of precipitates
∆
G
ε
=
5
×
10
6
Jm

3
;
∆
G
=
0 for incoherent precipitates
(a) Calculate the temperature below which both coherent and incoherent precipitation are
thermodynamically possible.
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 Spring '02
 CHEN

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