Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

17.3 Some Common Solid Engineering Materials 561

17.3 Some Common Solid Engineering Materials

In this section, we will briefly examine the chemical composition and common application of

some solid materials. We will discuss light metals, copper and its alloys, iron and steel, concrete,

wood, plastics, silicon, glass, and composite materials. Most of you will take a semester-long

materials class during your sophomore or junior year and will learn more in depth about the

atomic structure of various materials. Here our intent is to introduce you to some common

materials and their applications.

Lightweight Metals

Aluminum, titanium, and magnesium, because of their small densities (relative to steel), are

commonly referred to aslightweight metals. Because of their relatively high strength-to-weight

ratios, lightweight metals are used in many structural and aerospace applications.

Aluminumand its alloys have densities that are approximately one-third the density of

steel. Pure aluminum is very soft, thus it is generally used in electronics applications and in

making reflectors and foils. Because pure aluminum is soft and has a relatively small tensile

strength, it is alloyed with other metals to make it stronger, easier to weld, and to increase its

resistance to corrosive environments. Aluminum is commonly alloyed with copper (Cu), zinc

(Zn), magnesium (Mg), manganese (Mn), silicon (Si), and lithium (Li). The American National

Standards Institute (ANSI) assigns designation numbers to specify aluminum alloys. Generally

speaking, aluminum and its alloys resist corrosion; they are easy to mill and cut and can be

brazed or welded. Aluminum parts can also be joined using adhesives. They are good conduc-

tors of electricity and heat and thus have relatively high thermal conductivity and low electri-

cal resistance values. Aluminum is fabricated in sheets, plates, foil, rods, and wire and is extruded

to make window frames or automotive parts. You are already familiar with everyday examples

of common aluminum products, including beverage cans, household aluminum foil, nonrust

staples in tea bags, building insulation, and so on.

Titaniumhas an excellent strength-to-weight-ratio. Titanium is used in applications where rel-

atively high temperatures, exceeding 400up to 600C, are expected. Titanium alloys are used in

the fan blades and the compressor blades of the gas turbine engines of commercial and military air-

planes. In fact, without the use of titanium alloys, the engines on commercial airplanes would not

Lightweight and durable,

aluminum alloys are used

to produce a wide range

of products—from high-

performance engines to

soda cans. Source:Courtesy of Carroll Shelby Enterprises Source:Steve Allen / Brand X Pictures /PictureQuest

Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).

圀圀圀⸀夀䄀娀䐀䄀一倀刀䔀匀匀⸀䌀伀䴀圀圀圀⸀夀䄀娀䐀䄀一倀刀䔀匀匀⸀䌀伀䴀