[Chemistry Class Notes] on What is an Alloy? Pdf for Exam

An alloy is a substance which is formed when two or more metals are combined. They can also be formed when metals are combined with other elements. However, the properties which alloys exhibit are different from the individual properties of these elements. When you compare it to the pure metals, alloys are stronger and harder. Alloy examples include red gold which is made by combining gold and copper together. Another example of alloy includes white gold which is an amalgamation of silver and gold. Today, we will learn about what is an alloy in chemistry, alloy definition and constituents of alloy.

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Alloy Definition

Let us now learn what alloy means in chemistry. 

An alloy refers to a combination of two or more metals, or a metal combined with one or more elements. The resulting alloy has different properties than the original elements altogether, like increased strength and hardness. For example, when elemental iron is combined with non-metallic silicon or carbon, it yields steel or silicone steel. 

Constituents of Alloy

Now that you have learned about what the meaning of alloy is, let us look at what the constituents of alloy are. An alloy consists of two or more elements, either as a compound or a solution. The components of alloys are generally metals. However, carbon is an exception to being a non-metal and an important constituent of steel. Alloys are usually produced when the mixture of its constituents is melted.

Properties of Alloy

When you have learnt about what is meant by alloy, learning the properties of alloy becomes easier.

An alloy is a substance that has metallic properties and is composed of two or more elements, out of which at least one is a metal. A metal, having metallic properties, is a material, which, when freshly made, fractured, or polished, demonstrates a lustrous appearance. It also conducts heat and electricity as well. 

Metals are generally malleable, which means that they can be easily hammered into thin sheets. They are also ductile, meaning that they can be drawn into wires as well. A metal can either be a chemical element like iron, or an alloy like stainless steel. Most of the pure metals are either very brittle, soft, chemically reactive to be practically used. When different ratios of metals are combined as alloys, it modifies the original properties of metals to give desirable characteristics. Alloys are generally made to keep them less brittle, corrosion-resistant, harder, or even have a more desirable luster and color.

Therefore, alloying of metal helps us to use the metal in daily life application. This process also helps in making different types of metals perfect for use (by modifying its properties ).

Alloy Examples

Let us now look at some of the alloy examples.

Steel

Steel is an alloy of carbon and iron. It is a popular alloy because of its low cost and higher tensile strength. However, many different types of steels consist of different amounts of carbon along with several other elements like manganese, phosphorus, sulfur, chromium, copper, nickel, and molybdenum. Primarily, the composition of iron is accounted for by iron, which is at least 75% of the total alloy’s weight. It also consists of different amounts of carbon and many other elements depending on the type of steel. Since steel has higher tensile strength and affordability, it is used in the infrastructure and construction of buildings, bodies of vehicles and electrical appliances.

Bronze

Bronze is known to be an alloy of tin and copper. It is commonly used in heavy tools and gears, coins, medals, trophies and even in different forms of electrical hardware. The strength of bronze varies depending on the alloys that are used in the alloying. You must know that bronze is much superior compared to pure copper when it comes to hardness. It is also more ductile and machineable compared to pure copper.

Nichrome

Nichrome is an alloy of chromium and nickel. However, it is also common for the nichrome alloys to consist of iron and other similar elements. Nichrome is primarily used in resistance wires. It also has its application in several electrical appliances like bread toasters and space heaters. Nichrome alloys are also used in dental fillings.

Brass

It is a very common and useful alloy of copper. In this, the quantity of zinc is kept at 45%. Along with zinc, metals such as Sn, Mn , Al , Fe,Pb etc are also added in a small amount to obtain some special properties. There are many types of brass. These all have varying compositions of copper. For example – muntz brass, naval brass, aluminum brass, german silver, ordinary brass, Cap copper etc. These alloys have great strength, durability and machinability as compared to normal copper. Also, their melting point is lower than copper and zinc. These alloys are also corrosion, water resistant and have a good lifespan. Brass is used in making jewelry , forgings, rivets, screws. The cartridge brass is mostly used for making sheets and tubes. These alloys are also used in making decorative articles and marine propeller shafts.

Types of Alloy

Alloys are classified as :

• On the Basis of Principle Metal in the Alloy : Examples are copper alloy, iron alloy, lead alloy. A copper alloy has copper as a major constituent, i.e, Bronze. 

• On the Basis of Phases : There can be single phase alloys (consist of a uniform face) and double phase alloys ( consist of  two different phases). Example of single phase alloy is brass which has 30% Zn + 70 % Cu. Example of Double  phase alloys is muntz metal which has 60% Cu + 40% Zn. 

• On the Basis of Iron Content : On the basis of iron content, Alloys are classified as ferrous alloys and non ferrous alloys. The alloys which contain Fe as a constituent are known as ferrous alloys whereas the non-ferrous alloys do not contain Fe as a constituent. Example of ferrous alloys is Stainless steel made of Fe + Cr. Example of non-ferrous alloys is Solder which has Pb + Sn.