Page 61 - Manufacturing Engineering and Technology - Kalpakjian, Serope : Schmid, Steven R.

The Structure

of Metals

l.l Introduction 40
l.2 Types of Atomic ° This chapter introduces the subject of the crystalline structure of metals and
Bonds 4| explains why it is important in determining their properties and behavior.
|.3 The Crystal Structure ° It begins with a review of the types of atomic bonds and explains the importance
of Metals 42
|.4 Deformation and Strength of ionic, covalent, and metallic bonds.
of Single Crystals 44 ° Metal structures and the arrangement of atoms within the structure are then
l.5 Grains and Grain examined, and the types of imperfections in the crystal structure and their
Boundaries 47
l.6 Plastic Deformation effects are presented.
of Polycrystalline * Recognizing that even a small metal pin contains thousands of crystals, or
Metals 50 grains, the effects of grains and grain boundaries are examined, followed by a
I.1 Recovery, discussion of strain hardening and anisotropy of metals.
Recrystallization, and
Grain Growth 5| ° All of these topics are examined Within the framework of their relevance to
l.8 Cold, Warm, and Hot manufacturing processes.
Working 52
EXAMPLE:
|.I Number of Grains in l.l Introduction
the Ball of a Ballpoint
Pen 49
Why are some metals hard and others soft? Why are some metals brittle, while
others are ductile and thus can be shaped easily without fracture? Why is it that
some metals can withstand high temperatures, while others cannot? Why is it that a
sheet metal may behave differently when stretched in one direction versus another?
These and numerous other questions can be answered by studying the atomic
structure of metals-that is, the arrangement of the atoms within the metals-because
atomic structure greatly influences the properties and behavior of those metals. This
knowledge then guides us in controlling and predicting the behavior and performance
of metals in various manufacturing processes. Understanding the structure of metals
also allows us to predict and evaluate their properties, thus allowing us to make
appropriate selections for specific applications under various conditions. In addition
to atomic structure, several other factors influence the properties and behavior of
metals. Among these are the composition of the metal, impurities and vacancies in the
atomic structure, grain size, grain boundaries, environment, size and surface condi-
tion of the metal, and the methods by which metals are made into products.
The topics described in this chapter and their sequence are outlined in Fig. 1.1.
The structure and general properties of materials other than metals are described in

40

CHAPTER