An alloy is formed when a metal is mixed with other metals or with any of one or more chemical elements. They are made use of in a number of applications. Most of these combinations help to reduce the overall cost of the metal, while they continue to exhibit its properties. Some metal combinations impart other properties like higher mechanical strength or a resistance to corrosion.
Over 90 percent of the metals in use today comprise of alloys. They provide a number of products with useful properties. Once this combination takes place, the individual elements cannot be separated by any physical means. Alloys properties are distinct and depend on the various components in them. The main purpose of forming alloys is to create a metallic substance that has properties such as chemical, mechanical and physical, which are different from any of its component elements or metals. These properties can also change depending on how the alloy is formed or treated.
Mechanical working and treatments using heat can modify the chemical and physical properties of an alloy. As a rule, alloys are chemically more stable than any of its individual components. Alloys can be designed to have a specified resistance to various elements. These elements include temperature, fatigue, wear and corrosion or any other action that they may be subjected to. It is also possible to impart properties to alloys that increase their formability, their strength and add additional electrical or magnetic properties.
Steel is an alloy of iron that has the widest of uses and variations. It is formed by combining iron with chromium, nickel and other elements like carbon in small amounts. Each combination ensures that the steel so formed has some unique characteristics. Copper has high electrical conductivity, but low strength. The addition of beryllium makes the resulting alloy stronger and increases its electrical conductivity. Laser beam technology uses gallium arsenide to make an alloy that has superconducting properties.
Aircraft engines need alloys that have high resistance to heat and corrosion. And this is made possible by combining cobalt and nickel. On the other hand, beverage cans need to be strong and yet pliable. This is made possible by using the lightness of aluminium to combine with elements that include:
- Iron; and
Combining small amounts from each of these elements gives the resulting aluminium alloy the properties that beverage cans have. Brass is made from copper and zinc, while copper combined with tin makes for bronze. Both these alloys are very commonly used for plumbing fixtures, musical instruments and other things. On the other hand, tin with small amounts of copper and antimony produces the alloy known as pewter. Gold is another element which is very soft and not of much use in its original state. However, its combination with zinc, copper and nickel makes for 18 carat gold. This has 75% gold, durable and favoured for the making of ornaments.
Alloys are indeed a mixture of two or more elements of which one is a metal and makes for the primary or base metal. It is not necessary for the other constituents to be metals. However, they must be soluble into any mixture that is made during the process of melting the base metal. Once this combination of base metal and other elements crystallizes or solidifies, the mechanical property of the resultant alloy will be completely different from any that its individual constituents had.
So, a metal that is otherwise soft and malleable can be combined with other materials, to make it harder and stronger. In fact, very small amounts of carbon which is not a metal, produce the alloy steel when combined with iron. This gives it a strength and toughness that cannot be matched by the original iron. The properties of this alloy can be further modified by subjecting to varying forms of heat treatment, while addition of other elements can increase corrosion resistance.