Page 162 - Materials Science and Engineering An Introduction

134 • Chapter 4 / Imperfections in Solids

Processing/Structure/Properties/Performance Summary

In this chapter, we discussed several schemes used to specify concentration of one ele-
ment in another; equations were also provided to convert from one scheme to another.
During the processing of silicon to form integrated circuit components (Chapters 5
and 18), it is imperative that specification and control of impurity concentration be
extremely precise. These relationships are represented in the following concept map:

Silicon Specification of Diffusion in Fabrication of
Semiconductors composition semiconductors integrated circuits
(Processing) (Chapter 4) (Chapter 5) (Chapter 18)
4 m
m 1
C 1 = * 100
m 1 + m 2

The concept of a solid solution was also discussed. One form of solid solution in
an iron–carbon alloy, or steel (martensite), derives its high strength and hardness from
the formation of an interstitial solid solution (carbon dissolved in iron). The following
concept map represents this relationship:

Concept of Solid solution
Iron–Carbon Alloys solid solution strengthening
(Steels) (Processing)
(Chapter 4) (Chapters 7 & 10)
Tensile strength (MPa) 400

300

200
0 10 20 30 40 50
Nickel content (wt%)

With a knowledge of the characteristics of dislocation defects, we are able to un-
derstand the mechanisms by which metals [i.e., iron–carbon alloys (steels)] permanently
deform (Chapter 7), and, in addition, techniques that are used to improve the mechani-
cal properties of these materials. The following concept map notes this relationship:

Concept of Strengthening
Iron–Carbon Alloys
dislocation defects mechanisms
(Steels) (Properties)
(Chapter 4) (Chapters 7 & 10)