Figure 23 This ancient statue of horses from Venice, Italy, and this modern French horn are both made from copper alloys. The statue is made from bronze, an alloy of copper and tin. The French horn is made from brass, an alloy of copper and zinc.
Bronze is hard and durable enough to be used for propellers on ships and for statues, such as the statue of horses in Figure 23. A bronze bell has a clear, loud tone that lasts for several seconds.
A brass bell has a duller tone that dies away quickly. Brass is another alloy of copper that has been known for centuries. In its simplest form, brass contains only copper and zinc. Although both bronze and brass are alloys of copper, they have distinctly different properties. Brass is softer than bronze and is easier to shape into forms such as the French horn in Figure 23. Brass is shinier than bronze but is likely to weather more quickly.
Steel Alloys
The 1900s could be called the Age of Steel because of the skyscrapers, automobiles, and ships that were built from steel during the 1900s. Steel is an alloy of iron that contains small quantities of carbon, ranging from less than 0.2 percent to about 3 percent by mass. The smaller carbon atoms fit in the spaces between the larger iron atoms in the lattice. The carbon atoms form bonds with neighboring iron atoms. These bonds make the lattice harder and stronger than a lattice that contains only iron.
The properties of any particular type of steel depend on which elements other than iron and carbon are used and how much of those elements are included. Stainless steels contain more than 10 percent chromium by mass, but almost no carbon. Stainless steels are durable because chromium forms an oxide that protects the steel from rusting. But stainless steel is more brittle than steels that contain more carbon. The steel cables in the bridge in Figure 24 have to be strong enough to resist forces that might stretch the cables or cause them to break. The steel used contains sulfur, manganese, phosphorus, silicon, and 0.81 percent carbon.
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