Alloy - Definition, Examples, Types of Alloys with FAQs,

What is an alloy in chemistry?

Alloy definition: A substance created from the mixing of two or more metals is referred to as an alloy.
Combinations of metals and other elements can also be used to create alloys. The properties of alloys are frequently dissimilar to the qualities of their constituent components. When compared to pure metals, alloys frequently have greater strength and hardness. Red gold, which is made by combining copper and gold, is an example of an alloy. White gold, which is made by combining silver and gold, is another major gold alloy.

Alloys can be solid solutions of metallic elements, with all individual grains/crystals of the metals having the same composition, or combinations of metallic phases with at least two different solutions, resulting in microstructures including different types of crystals within the alloy. Alloys with well-defined crystal structures and stoichiometry are referred to as "intermetallic compounds." Additionally, in some situations, Zintl phases (results of chemical interactions between alkali metals or alkaline earth metals and post-transition metals or metalloids) can be classified as alloys.

Alloys are known to feature metallic bonding. For almost all practical applications, the constituents of an alloy are measured in terms of their mass percentage. However, for some scientific studies, the components of alloys are measured in terms of their atomic fractions. It is important to note that alloys can be classified into two categories based on the arrangements of atoms in their respective lattices: substitutional alloys and interstitial alloys. It can also be noted that alloys can be classified based on the total number of phases present. For example, homogeneous alloys feature only one phase and heterogeneous alloys feature two or more phases.

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Examples of alloys.

Babbitt metal, commonly known as bearing metal, is an alloy used primarily as a bearing surface in simple bearings. Isaac Babbitt, an American inventor, created this alloy in the year 1839. The following is a typical Babbitt metal composition:

90 percent tin (Sn)

7 percent antimony (Sb)

Copper (Cu) accounts for 3% of the total.

One of the most appealing properties of this alloy is it has minimal friction with steel.

The chemistry of alloys

A strong electron microscope can reveal the atoms inside a metal. Then the atoms are grouped in a regular arrangement called a crystalline lattice.

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Types of alloys

substitution Alloy

A replacement alloy is formed when the atoms of the alloying agent replace the atoms of the primary metal. Only if the atoms of the base metal and the alloying agent are nearly the same size can an alloy like this form. In most replacement alloys, the constituent elements are close in the periodic table to one another. Brass, for example, is a copper-based substitution alloy in which zinc atoms replace 10–35 percent of the copper atoms that are ordinarily present. Because copper and zinc are near in the periodic table and contain atoms that are roughly the same size, brass works well as an alloy.

Interstitial Alloy

Alloys with interstitial spaces

Alloys can also occur when the alloying agent or agents have atoms that are significantly smaller than the parent metals. The agent atoms then slide between the gaps of metal forming an interstitial alloy. One of the examples of an interstitial alloy is steel where a small number of carbon atoms slide between the massive atoms in an iron crystalline lattice.

Bell Metal

Bell metal is an alloy that is predominantly used in the manufacture of bells and other similar instruments (thus the name). It is a type of bronze that contains a significant quantity of tin in its composition. Bell metal is an alloy of copper and tin. Bell metal is often made up of the following elements:

Copper (Cu) accounts for 78 percent of the total.

Tin (Sn) accounts for 22% of the total.

Cooking and dining utensils are also made of this alloy. It can also be found in some styles of home decor.

Bronze

Bronze is a copper and tin alloy. Medals, coins, trophies, hefty gears and tools, and several types of electrical devices all employ it. Bronze is an alloy of elements copper and tin.

Bronze composition:

Copper (Cu) accounts for 75% of the total.

Tin (Sn) - contains up to 12%

Manganese, aluminium, zinc, nickel, silicon, phosphorus, and arsenic are examples of other elements.

It should be noted that the strength of the bronze varies depending on the components employed in the alloying process. It should be noted that bronze has a far higher hardness than pure copper. It's also more ductile and machinable than pure copper.

Nichrome

Nichrome is an alloy made mostly of nickel and chromium, as the name implies. It's not uncommon for nichrome alloys to contain iron and other elements as well. The following is a typical nichrome alloy composition:

Nickel (Ni) contains 80-85% chromium (Cr) Iron and other elements account for 15-20% of the total.

Resistance wires are the most common use of nichrome. Certain electrical equipment, such as space heaters and bread toasters, employ it as the heating element. It's also worth noting that nichrome alloys are used in certain types of dental fillings.

Steel

It is largely an iron and carbon alloy. Different varieties of steel, on the other hand, are known to have various levels of carbon, as well as other elements (such as chromium, manganese, sulphur, phosphorus, nickel, copper, and molybdenum). Iron makes up the majority of steel's composition (it typically accounts for at least 75% of the alloy's weight). Depending on the type of steel, it may also contain variable levels of carbon and other metals. Stainless steel, for example, is made up of the following elements:

Iron (Fe) content is between 85 and 88 percent

A chromium (Cr) content of at least 10.5 percent is required

Carbon (C) emissions are less than 1.2 percent

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NCERT Chemistry Notes:

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