Alloys: Meaning, Properties and Uses

Alloys: The mechanical properties of pure metals are poor. As a result, they aren’t used in their purest form in the industry. The addition of other elements alters their properties. Alloys have properties that differ from the metal in which they are contained, such as strength, hardness, durability, ductility, tensile strength, and toughness. As a result, they are more useful than pure metals alone.

For example, bronze (copper and tin) is used to make bells, hammers, and other items. Steels derived from iron alloys are used to construct automobile bodies and railway lines.

In this article, we will study alloys’ meaning and properties and some of the common alloys used commercially.

What are Alloys?

An alloy is a chemical element mixture that produces an impure substance (admixture) with metal-like properties. An alloy differs from an impure metal in that the added elements in an alloy are well controlled to produce desirable properties. In contrast, impure metals such as wrought iron are less controlled but are frequently considered useful. Alloys are created by combining two or more elements, one of which must be a metal. This is commonly referred to as the primary metal or the base metal, and the name of the metal may also be the name of the alloy. The other constituents may or may not be metals, but they will be soluble and dissolve into the mixture when mixed with the molten base. The mechanical properties of alloys are frequently quite different from those of their constituents.

An alloy can be a solid solution of metal elements (a single phase with identical metallic grains (crystals)) or a mixture of metallic phases (two or more solutions, forming a microstructure of different crystals within the metal). Intermetallic compounds are alloys that have a specific stoichiometry and crystal structure. Furthermore, in some cases, Zintl phases (products of chemical reactions between alkali metals or alkaline earth metals and transition metals or metalloids) can be classified as alloys.

Alloys are distinguished by their metallic bonding properties. In practical applications, alloy constituents are typically measured by mass percentage, while in basic science studies, they are measured by an atomic fraction.  Based on their atomic arrangement, alloys are typically classified as substitutional or interstitial. They can also be homogeneous (consisting of a single-phase), heterogeneous (consisting of two or more phases), or intermetallic.

Alloying Process

Metals are alloyed by combining them with one or more other elements. The most common and oldest alloying process involves heating the base metal beyond its melting point and then dissolving the solutes into the molten liquid, which may be possible even if the solute’s melting point is much higher than the metal itself.

Some metals and solutes, such as iron and carbon, have extremely high melting points and are impossible to melt. As a result, alloying can also be done with one or more constituents in a gaseous state, such as in a blast furnace. It can also be done with one, more, or all of the constituents in the solid-state, as in ancient methods of pattern welding (solid-solid), shear steel production (solid-solid), or crucible steel production (solid-liquid), mixing the elements through solid-state diffusion.

Properties of Alloys

Since elements do not simply combine to form a sum of the parts, it is difficult to calculate the precise properties of new alloys. They form as a result of chemical interactions that are determined by the component parts and specifications.

Individual pure metals may have useful properties such as good electrical conductivity, high strength and hardness, or resistance to heat and corrosion. Commercial metal alloys attempt to combine these advantageous properties in order to produce metals that are more useful for specific applications than any of their constituent elements.

Alloys are harder and tougher than base metals, and they are corrosion resistant. They are inert to common chemicals, magnetisable, and ductile.

Examples of Alloys

Babbit Metal

Babbitt metal, also known as bearing metal, is an alloy that is primarily used as a bearing surface in plain bearings. Isaac Babbitt, an American inventor, invented this alloy in \(1839.\) Babbitt metal is typically composed of the following elements:

Tin \(\left({{\text{Sn}}} \right)\) is \({\rm{90\% }}\\) pure, antimony \(\left({{\text{Sb}}} \right)\) is \({\rm{7\% }}\) pure, and copper \(\left({{\text{Cu}}} \right)\) is \({\rm{3\% }}\) pure.
This alloy’s low coefficient of friction with steel is one of its most desirable properties.

Bell Metal

Bell metal is an alloy that is primarily used in the manufacture of bells and other related instruments (hence the name “Bell” metal). It is a type of bronze that contains a relatively high amount of tin in its composition. Bell metal is typically composed of \(78\% \) copper \(\left({{\text{Cu}}} \right)\) and \(72\% \) tin \(\left({{\text{Sn}}} \right).\)

This alloy is also used in the manufacture of cooking and eating utensils. It is also used in some types of home decor.

Bronze

Bronze was the first alloy discovered, and it is composed of \(85 – 88\% \) copper, \(12 – 12.5\% \) tin, and small amounts of other metals such as aluminium, manganese, zinc, or nickel. The purpose of this mixture is to improve the properties of copper.

Bronze is used in the production of sculptures, musical instruments, medals, and industrial applications.

Steel

Steel is an iron alloy with about \(1\% \) carbon and may contain other elements such as manganese. Steel is manufactured because it is tough, hard, and corrosion-resistant.

As a low-cost alloy, steel is widely used in the construction of roads, railways, airports, bridges, skyscrapers, and other structures, as well as in the manufacture of major appliances and various construction materials, household products, and so on.

Brass

The only difference between brass and bronze is that bronze is an alloy of copper and tin. In contrast, brass is an alloy of copper and zinc with other elements such as arsenic, lead, phosphorus, aluminium, manganese, and silicon. The purpose of this alloy is to improve its electrical and mechanical properties.

Brass is used in the production of ornamental items, locks, zippers, gears, doorknobs, musical instruments, and so on. It is also used in plumbing and electrical applications.

Solder

Solder is a fusible metal alloy that is used to permanently connect metal workpieces. It’s tin and leads alloy with traces of other metals.

This alloy is used to create a long-lasting connection between electrical components.

Wood’s Metal

Wood’s metal is an alloy made up of \(50\% \) bismuth, \(26.7\% \) lead, \(13.3\% \) tin, and \(10\% \) cadmium by weight. Barnabas Wood created the metal alloy from wood.

Wood’s metal is commonly used as a valve element in fire sprinkler systems installed in buildings. It is also used in machine shops, technical laboratories, antique restoration, and so on.

Nichrome

Nichrome is a group of nickel, chromium, and iron alloys. This alloy is commonly used to make resistance wire. It has a high melting point, low manufacturing cost, strength, ductility, electron flow resistance, and oxidation resistance. Because of all of these properties, nichrome is widely used in heating elements.

It is used in the explosives and fireworks industries and the production of heating elements.

Alloyed Gold

The purest form of gold, \(24\)- carat gold, is very soft and cannot be moulded into jewellery, and therefore, copper or silver is added to it to give it hardness and strength.

To convert \(24\)-carat gold to \(22\)-carat gold with a purity of approximately \(91.6\% ,\) approximately \(8.4\% \) copper or silver is added. The majority of jewellery is made of \(22\)-carat gold.

Summary

We can conclude that alloys are a homogeneous mixture of two or more metallic solutions. Alloys are harder and tougher than base metals, and they are corrosion resistant. They are inert to common chemicals, magnetisable, and ductile. Alloying can be done by one of the most common and oldest processes that involve heating the base metal beyond its melting point and then dissolving the solutes into the molten liquid. We also studied some of the common alloys like bronze, steel, nichrome, etc., and some of the common alloying elements include manganese, nickel, vanadium, chromium and molybdenum.

Now we know some of the important uses of alloys in our daily life- like in the making of cooking utensils, construction of railway tracks, parts of vehicles and many other things.

FAQs on Alloys

Q.1. What do you mean by alloys?
Ans: Alloys are two or more elemental mixtures that are homogeneous. Two metals or a metal and a nonmetal could be used. To make an alloy, first, melt the metal and then dissolve the other elements in it. Steel, for example, is an iron-carbon alloy.

Q.2. What is the example of alloys?
Ans: An alloy is a metallic-solid solution or a mixture of two or more elements. Alloys include metals like brass, pewter, phosphor bronze, amalgam, and steel.

Q.3. What are the five alloys?
Ans: Some of the important alloys include-
1. Steel
2. Nichrome
3. Bronze
4. Brass
5. Solder

Q.4. Which elements are commonly used for alloying?
Ans: Some of the common alloying elements include-
1. Manganese
2. Nickel
3. Vanadium
4. Chromium
5. Molybdenum

Q.5. How are alloys formed?
Ans: Metals are alloyed by combining them with one or more other elements. The most common and oldest alloying process involves heating the base metal beyond its melting point and then dissolving the solutes into the molten liquid, which may be possible even if the solute’s melting point is much higher than the metal itself.

Q.6. What are the three properties of alloys?
Ans: Alloys, in general, are stronger and harder, less malleable, less ductile, and more corrosion-resistant than the alloy’s main metal. An alloy mixture is stronger because it contains atoms of different sizes from different elements.

Learn Chemical Properties Of Metals Here

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