8.12: Alloys

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What are the best guitar strings to use?

Many guitar players are very meticulous when it comes to their guitar strings. There is a variety to select from, dependent on the type of guitar and the style of music. Electric guitars need steel strings so that the magnetic pick-up will detect the string vibrations. Acoustic guitar players have several choices; bronze strings (mixed with different amounts of copper and zinc) have perhaps the brightest tone. There are several combinations of bronze alloys to choose from. For those with a high budget, titanium strings are available. Gold coating also helps string life and makes its unique contribution to tone. Alloy chemistry has contributed greatly to the strength, durability, and tonal quality of guitar strings.

Alloys

An alloy is a mixture composed of two or more elements, at least one of which is a metal. You are probably familiar with some alloys such as brass and bronze. Brass is an alloy of copper and zinc. Bronze is an alloy of copper and tin. Alloys are commonly used in manufactured items because the properties of these metal mixtures are often superior to a pure metal. Bronze is harder than copper and more easily cast. Brass is very malleable and its acoustic properties make it useful for musical instruments.

Figure \(\PageIndex{2}\): Bronze, an alloy of copper and tin, has been in use since ancient times. The Bronze Age saw the increased use of metals rather than stone for weapons, tools, and decorative objects. Brass, an alloy of copper and zinc, is widely used in musical instruments like the trumpet and trombone. (Credit: (A) Davide Ferro; (B) Guillaume Piolle; Source: (A) http://commons.wikimedia.org/wiki/File:Ancient_bronze_greek_helmet_-South_Italy.jpg(opens in new window); (B) http://commons.wikimedia.org/wiki/File:Trompette_piccolo_-_pavillon.jpg(opens in new window); License: CC by 2.0(opens in new window))

Steels are a very important class of alloys. The many types of steels are primarily composed of iron, with various amounts of the elements carbon, chromium, manganese, nickel, molybdenum, and boron. Steels are widely used in building construction because of their strength, hardness, and resistance to corrosion. Most large modern structures like skyscrapers and stadiums are supported by a steel skeleton (see figure below).

Figure \(\PageIndex{3}\): The Willis Tower (formerly called the Sears Tower) in Chicago was once the tallest building in the world, and is still the tallest in the Western Hemisphere. The use of steel columns makes it possible to build taller, stronger, and lighter buildings. (Credit: User:Soakologist/Wikipedia; Source: http://commons.wikimedia.org/wiki/File:Sears_Tower_ss.jpg(opens in new window); License: The copyright holder of this work allows anyone to use it for any purpose including unrestricted redistribution, commercial use, and modification)

Alloys can be one of two general types. In one type, called a substitutional alloy, the various atoms simply replace each other in the crystal structure. In another type, called an interstitial alloy, the smaller atoms such as carbon fit in between the larger atoms in the crystal packing arrangement.

Summary

Alloys are mixtures of materials, at least one of which is a metal.
Bronze alloys were widely used in weapons.
Brass alloys have long been employed in musical instruments.
Steel alloys are strong and durable.

Review

What is brass made of?
What is bronze made of?
Why is steel widely used in construction?
What is a substitutional alloy?