Fundamentals of Materials Science and Engineering: An Integrated Approach, 3e

GTBL042-13 GTBL042-Callister-v2 August 29, 2007 8:52

540 • Chapter 13 / Types and Applications of Materials

steel cans (tin cans) that are used for food containers; this coating inhibits chemical

reactions between the steel and the food products.

Unalloyed zinc also is a relatively soft metal having a low melting temperature

and a subambient recrystallization temperature. Chemically, it is reactive in a num-

ber of common environments and, therefore, susceptible to corrosion. Galvanized

steel is just plain carbon steel that has been coated with a thin zinc layer; the zinc

preferentially corrodes and protects the steel (Section 16.9). Typical applications of

galvanized steel are familiar (sheet metal, fences, screen, screws, etc.). Common ap-

plications of zinc alloys include padlocks, plumbing fixtures, automotive parts (door

handles and grilles), and office equipment.

Although zirconium is relatively abundant in the earth’s crust, it was not until

quite recent times that commercial refining techniques were developed. Zirconium

and its alloys are ductile and have other mechanical characteristics that are com-

parable to those of titanium alloys and the austenitic stainless steels. However, the

primary asset of these alloys is their resistance to corrosion in a host of corrosive me-

dia, including superheated water. Furthermore, zirconium is transparent to thermal

neutrons, so that its alloys have been used as cladding for uranium fuel in water-

cooled nuclear reactors. In terms of cost, these alloys are also often the materials

of choice for heat exchangers, reactor vessels, and piping systems for the chemical-

processing and nuclear industries. They are also used in incendiary ordnance and in

sealing devices for vacuum tubes.

In Appendix B is tabulated a wide variety of properties (e.g., density, elastic mod-

ulus, yield and tensile strengths, electrical resistivity, coefficient of thermal expansion,

etc.) for a large number of metals and alloys.

Types of Ceramics

The preceding discussions of the properties of materials have demonstrated that

there is a significant disparity between the physical characteristics of metals and

ceramics. Consequently, these materials are utilized in totally different kinds of ap-

plications and, in this regard, tend to complement each other and also the polymers.

Most ceramic materials fall into an application-classification scheme that includes

the following groups: glasses, structural clay products, whitewares, refractories, abra-

sives, cements, and the newly developed advanced ceramics. Figure 13.7 presents a

Ceramic materials

Glasses

Glasses Glass-

ceramics

Structural

clay products

Whitewares Fireclay Silica Basic Special

Clay products Refractories Abrasives Cements Advanced

ceramics

Figure 13.7 Classification of ceramic materials on the basis of application.