Pure metals are usually never used in industries for manufacturing purposes. Usually, we observe that a combination of metals is used to enhance the properties of a single metal.
We know that your metals have certain important physical properties such as density, malleability, ductility, conductivity, boiling point, melting point etc. However, these properties can be slightly changed and also enhanced by mixing two or more metals together as per the need.
This combination of metals is known as an alloy. An alloy is a homogeneous mixture of two or more metals. It may also contain metal and non-metal. Alloys give more strength and last for a longer time as compared to metals.
Alloys have certain advantages over metals. Some of them are as follows.
An alloy has more tensile strength than its constituent elements. We can increase the hardness of a metal by mixing it with another metal or nonmetal.
Metals melt at very high temperatures. When a pure metal is alloyed with another metal or nonmetal, its melting point reduces.
Metals are extremely susceptible to chemical and weather attacks. Alloys, on the other hand, are more resistant to corrosion. When a metal is alloyed, it becomes inert, thereby enhancing its corrosion resistance.
Alloying can be used to change the colour of the base metal. By mixing another metal or nonmetal, the alloy so formed will have a different colour.
When pure metals are solidified after melting, they tend to contract a little. However, when they are alloyed, they tend to expand on solidification. This helps to obtain good castings.
Bronze was the first to be discovered; it is a mixture of copper (88%) and tin (12%). Very small quantities of zinc, nickel or manganese may be added to improve the overall properties.
Steel is made by mixing iron and carbon (1%). It is harder and resistant to corrosion.
Brass is made by mixing copper (60-85%) and zinc (15-40%). Other elements may be added in smaller proportions. Brass is made to enhance the electrical properties of copper.
Alnico is an alloy formed by mixing iron with nickel, cobalt and aluminium (Al-Ni-Co). It is a ferromagnetic substance and is used in permanent magnets.
Solder is an alloy of tin and lead. It has a low melting point and is used to repair or join two pieces of metals.
Cast iron is formed by mixing iron (96-98%) with carbon (2-4%). Some traces of silicon may also be found. This alloy has a good castability, doesn't get deformed and has a low melting point.
Sterling silver is formed by mixing 92.5% silver with 7.5% of another metal, usually copper. Silver gets corroded and turns black if the air contains sulphur compounds. In order to reduce the tarnishing of silver, copper or other metals can be mixed to form this alloy.
Nichrome is an alloy formed using nickel, chromium and iron. It has a very high resistance, a high melting point, ductility etc. It offers resistance to the flow of electrons and does not get oxidized easily.
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Alloys have wide ranging applications in our everyday life. Some of the most common uses of alloys are as follows:
Mini sculptures, medals and some musical instruments are made from bronze.
Steel is used for construction of railways, bridges, roads, airports etc. It is also used for making household utensils and other products.
Locks, door handles, door knobs, electrical appliances, zippers, musical instruments, decoration and gifting items are made from brass.
Permanent magnets are made from alnico.
Solder is used to permanently join electrical components.
Sterling silver is used to make surgical instruments, musical instruments, cutlery and pieces of jewellery.
Alloys of aluminium are lightweight, therefore used for making bodies of aircrafts and their parts.
Alloys of titanium are extensively used in the aerospace industry because of their high temperature strength and superplastic behaviour.
Amalgam which is an alloy of mercury, is used for medical activities. It is also used to fill tooth cavities.
Certain alloys of gold such as rose gold, are used for jewellery making purposes.
Many alloys that contain silver in their name usually do not contain silver as one of their constituent elements. They are called 'silver' only because of their colour. Examples of this are Tibetan silver and German silver.
Stainless steel, which is formed by mixing iron, small quantities of carbon and chromium is called 'stainless' because chromium gives it resistance from any kind of stain or iron rust. The chromium reacts with oxygen to form a thin layer of chromium oxide, which acts as the protective layer against any further corrosion.
Question 1: Explain the Difference Between Steel and Stainless Physics.
Solution: Steel is formed when carbon is added to iron to increase its hardness. Steel has a higher carbon content and a low melting point. Stainless steel contains a higher amount of chromium. This chromium forms a layer of chromium oxide that acts as a barrier against corrosion. It does not allow any stains or marks to appear on the surface. This is why stainless steel does not get rusted or corroded.
So, containing higher carbon content has more strength as compared to stainless steel. Steel is used for manufacturing bridges, railways and buildings. Stainless steel on the other hand, is mostly used for making utensils and household items.
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Question 2: What is the Application of Alloys in the Aerospace Industry?
Solution: Aluminium is a lightweight metal and its alloys are widely used in the aerospace industry. Specially designed alloys allow the aircraft industry to manufacture high strength parts for jet engines. These parts have to deal with the extremities of pressure, temperature and vibration. Stainless steel, nickel, copper, titanium and their alloys are used for making engine blocks. They also provide high strength and the ability to function at very high temperatures. These alloys are designed to have extreme strength, corrosion resistance and efficiency at unusually high temperatures.