Page 36 - Materials Science and Engineering An Introduction

8 • Chapter 1 / Introduction

Figure 1.6
Bar chart of room- Metals
temperature strength Composites
(i.e., tensile strength) Steel Ceramics
Strength (tensile strength, in units of megapascals) (logarithmic scale) 100 Gold Glass PS Polymers Woods
values for various 1000 alloys N CFRC
metals, ceramics, Cu,Ti Si 3 4 GFRC
polymers, and alloys Al O SiC
composite materials. Aluminum 2 3
alloys
Nylon
PVC

10 PE PTFE

(Figure 1.8) and heat, and are not transparent to visible light; a polished metal surface
has a lustrous appearance. In addition, some of the metals (i.e., Fe, Co, and Ni) have
desirable magnetic properties.
Figure 1.9 shows several common and familiar objects that are made of metallic materials.
Furthermore, the types and applications of metals and their alloys are discussed in Chapter 11.

Ceramics
Ceramics are compounds between metallic and nonmetallic elements; they are most fre-
quently oxides, nitrides, and carbides. For example, common ceramic materials include
aluminum oxide (or alumina, Al 2 O 3 ), silicon dioxide (or silica, SiO 2 ), silicon carbide (SiC),
silicon nitride (Si 3 N 4 ), and, in addition, what some refer to as the traditional ceramics—those
composed of clay minerals (e.g., porcelain), as well as cement and glass. With regard to me-
chanical behavior, ceramic materials are relatively stiff and strong—stiffnesses and strengths
Tutorial Video:
Ceramics are comparable to those of the metals (Figures 1.5 and 1.6). In addition, they are typically
very hard. Historically, ceramics have exhibited extreme brittleness (lack of ductility) and are
highly susceptible to fracture (Figure 1.7). However, newer ceramics are being engineered
to have improved resistance to fracture; these materials are used for cookware, cutlery, and

Figure 1.7
Bar chart of Metals
room-temperature Steel
resistance to fracture 100 alloys Composites
(i.e., fracture tough- Titanium
alloys
ness) for various
metals, ceramics, Aluminum CFRC GFRC
alloys
polymers, and
composite materials. 10
(Reprinted from Resistance to Fracture (fracture toughness, in units of MPa m) (logarithmic scale) Ceramics Polymers
Engineering Materials Si N
3
1: An Introduction to Al O 4 Nylon
2 3
Properties, Applications SiC Polystyrene
and Design, third 1.0 Polyethylene
edition, M. F. Ashby and Wood
D. R. H. Jones, pages Polyester
177 and 178, Copyright Glass
2005, with permission Concrete
from Elsevier.)
0.1