In this article, you will learn the complete overview of alloys such as their definition, types, properties, purpose of alloying, uses, and many more.
In our previous article, we learned about the different types of metals and their uses.
Metal can be classified into three categories which are: Ferrous Metal, Non-Ferrous Metal, and Alloys.
Here we will discuss only alloy.
So without wasting time let's get started.
What is an Alloy?
A Substance that is composed of two or more chemical elements such that metallic atoms Predominate in composition and the metallic bond Predominates is called an "alloy".
The homogeneous mixture of two or more metals, or a metal and a non-metal is called an alloy.
Generally, alloys are prepared by fusing together the different ingredients (metals) in a furnace. The alloys exhibit different properties when compared with the properties of metals in them.
Properties of Alloy
Alloys have some well-known properties:
- It has more tensile strength.
- It has more toughness.
- It is corrosion-resistant.
- It is harder than metal which is soft.
- It has high durability.
- It has more ductility.
Purpose of Alloying
The following are the purposes of alloying:
- To Improve Hardness
- To lower the Melting point
- To Increase the Corrosion Resistance
- To Increase Tensile Strength
- To Improve Casting Property
- To Modify the Colour
- To Modify the Chemical Activity
To Improve Hardness
When the metal is alloyed by metal or non-metal it becomes hard
For example, pure iron is generally soft and has become hard when carbon is added to them.
To lower the Melting point
When alloying metal is added to base metal it acts as impurities in the base metal and the melting point of base metal is lowered thus, alloying makes the metal easily fusible. So, this property of metal is used in making useful low-melting alloys.
For example, wood metal alloy (Pb + Bi + Cd + Sn) has a melting point of 71°c which is lower than component metal.
To Increase the Corrosion Resistance
To Increase the corrosion resistance cu is mixed with Sn and fe is mixed with cr.
For example bronze (cu-sn), brass (cu-zn), stainless steel (fe-c-cr-ni)
To Increase Tensile Strength
When metal is alloyed by pure or proper elements such as Ni, Cr, V, etc. Then the tensile strength will increase.
For example, if carbon is added to pure iron then its tensile strength will increase ten times.
To Improve Casting Property
To improve the castability by 5% Sn (Tin) is an alloy with 2% (sb) antimony.
For example duralumin (an alloy of Al - Cu - Mg-Mn) and Bronze (an alloy of cu-sn).
To Modify the Colour
Red gold (95% Au and 25% cu)
Rose gold (75% gold and 22.25% cu)
To Modify the Chemical Activity
When the metal is alloyed by a different metal then the chemical property will change as per their alloying.
For example, the chemical activity of sodium reduces on alloying with mercury while the activity of aluminum increases an alloying with mercury.
Types of Alloy
Alloy can be classified into two types:
- Ferrous Alloy
- Non-Ferrous Alloy
Show in the figure different types of alloys which are described below in detail.
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| Alloy |
Ferrous Alloy
Those alloys which contain iron as the main (major) constituent are called ferrous alloys.
Types of Ferrous Alloy
Ferrous Alloy can be classified into the following types:
- High-Speed Steel
- Nickel Steel
- Nickel Cobalt Steel
- Nickel Chromium Steel
- Vanadium Steel
- Manganese Steel
- Silicon Steel
- Cobalt Steel
- Molybdenum Steel
- Stainless Steel
All these ferrous alloys also come under the type of alloy steel.
High-Speed Steel
High-speed steel is made by adding tungsten to steel, hence it is also known as tungsten steel.
Tungsten steel is very hard and maintains its hardness even at high temperatures.
It is used in making cutting tools, drill bits, hex blades, cutters, reamers, etc.
According to the amount of tungsten, it is of three types:
- Super High-Speed Steel
- Medium-High Speed Steel
- Low High-Speed Steel
Super High-Speed Steel
It contains 22% tungsten, chromium 4%, and vanadium up to 1%.
Medium-High Speed Steel
It contains tungsten 18%, chromium 4%, and vanadium 1%.
Low High-Speed Steel
It contains tungsten 14%, chromium 4%, and vanadium 1%.
Nickel Steel
It contains up to 4% nickel metal.
Its hardness, elastic limit, and tensile strength are high and it does not rust easily.
It is used in making rivets, pipes, axles, and parts of aircraft and engines.
Nickel Cobalt Steel
If 30% to 35% nickel and 5% cobalt are added to the steel, it is called nickel-cobalt steel.
It is also called Invar steel.
Its coefficient of expansion is very less that's why it is used as a precision instrument.
Nickel Chrome Steel
The steel in which 0.5% to 1% carbon, 0.3% to 0.8% manganese, 3% to 5% nickel, and 0.5% to 1.8% chromium are mixed is called nickel chrome steel.
This increases the elastic limit, reduces wear, and also increases hardness and tensile strength.
It is used in making cutlery, automobile parts, cutting tools, etc.
Vanadium Steel
The steel in which 1.5% carbon, 12.5% tungsten, 4.5% chromium, 5% cobalt, and 5% vanadium is added is called vanadium steel.
Due to this, its elastic limit and tensile strength increase, and the ability to tolerate strong shocks arise.
It is mostly used for making tools and cutters.
Manganese Steel
The steel in which 1.0% to 1.9% manganese, and 0.4% to 0.8% carbon are mixed is called manganese steel.
It is also called special high alloy steel.
It wears less.
It is used in making rail lines, grinders, etc.
Silicon Steel
Silicon is mixed in this steel in varying amounts from 1% to 14% according to the work.
It is heat resistant.
It does not rust.
Cobalt Steel
The steel which contains 0.5% to 1.5% high carbon and 5% to 35% cobalt is called cobalt steel.
It has more toughness, tensile strength, and magnetic properties, so it is mostly used for making permanent magnets and more sharp tools.
Molybdenum Steel
The amount of molybdenum in it is very heavy.
It contains molybdenum 4.5% to 9%, carbon 0.8 to 1.5%, chromium 4%, and vanadium 1 to 5%.
On mixing these metals in it, a lot of hardness and toughness come.
It is used to make bearings, motor vehicles, airplanes, etc.
Stainless Steel
If nickel 8%, chromium 18%, molybdenum 2%, and carbon 0.2 to 0.6% are mixed in steel, then it is called stainless steel.
Stainless steels generally contain more than 10% chromium as the main alloying element and are valued for high corrosion resistance. It does not stain, corrode or rust as easily as ordinary steel that's why it is called stainless steel.
Stainless steels have a sufficient amount of chromium present so that a passive film of chromium oxide forms which adheres to the metal surface very tightly and prevents further corrosion.
It is very hard, tough, acid-resistant, and corrosion-resistant.
It does not rust.
It cannot be hardened.
It is often used to make household utensils, watch parts, automobile parts, cars, knives, and airplanes.
These stainless steels can be divided into three groups based on their crystalline structure:
- Austenitic Stainless Steel
- Ferritic Stainless Steel
- Martensitic Stainless Steel
Austenitic Stainless Steel
It contains 18-26% chromium (Cr) and 8-22% nickel (Ni) and less than 0.8% carbon.
It is non-magnetic and non-heat-treatable.
Ferritic Stainless Steel
It contains trace amounts of nickel, 12-17% chromium, and less than 0.2% carbon, along with other alloying elements, such as molybdenum, aluminum, or titanium.
These magnetic steels cannot be hardened by heat treatment but can be strengthened by cold working.
Martensitic Stainless Steel
It contains 11-17% chromium, less than 0.4% nickel, and up to 1.2% carbon.
These are magnetic and are similar in composition to the ferritic group but contain higher carbon and lower chromium to permit hardening by heat treatment.
Non-Ferrous Alloy
Those alloys which do not contain iron as the main constituent are called non-ferrous alloys.
Types of Non-Ferrous Alloy
Non-Ferrous Alloys can be classified into the following types:
- Nichrome
- Dutch Metal
- German Silver
- Gun Metal
- Brass
- Bronze
- Solder
- Duralumin
- Babbitt Metal
- Y Alloy
- Magnelium
Nichrome
It contains 60% nickel, 12% chromium, 2% manganese, and 26% iron.
It is used in making resistance coils, heating elements in stoves, electric irons, water heaters, toasters, etc.
Dutch Metal
It contains 80% copper and 20% zinc.
It is used for making cheap jewelry, musical instruments, battery caps, and flexible hoses.
German Silver
It contains 50% copper, 30% nickel, and 20% zinc.
It is used for making coins, ornaments, and decorative materials.
Gun Metal
It contains 88% copper, 10% tin, and 2 % zink.
It is used for making bearings, coins, hydraulic fittings, etc.
Brass
Copper in this metal is 60 to 80%, and zinc is 20 to 40%.
The machinability of this alloy is improved by adding a small amount of lead.
It is ductile and impact resistant.
It is used for making utensils, tubes, and sheets.
Bronze
It contains 90% copper and 10% tin.
It is used for making decorative items, medals, artwork, pots, pans, etc.
Solder
It contains tin 35% to 50%, leads 50% to 63%, and antimony in some quantity.
It is a shiny and soft metal that melts quickly.
It is used for soldering.
Duralumin
It contains aluminum 95%, copper 4%, magnesium 0.5%, and manganese 0.5%.
It is strong, light, and corrosion-resistant.
Airplanes are made from it.
Babbitt Metal
It contains 88% tin, 4% copper, and 8% antimony.
It is a soft and less wearable metal.
It is also used to make good-quality bearings.
Y Alloy
It is also called copper-aluminum alloy. The addition of copper to pure aluminum increases its strength and machinability.
This alloy contains 92.5% aluminum and 4% Cu 2% Ni and 1.5% Mg.
Its strength at 200° C is better than aluminum. It retains its high strength and hardness at high temperatures.
It is used for the piston cylinder head, crankcases of the IC engine, etc.
It is much used in aircraft engines.
Magnelium
It is made by melting the aluminum with magnesium in a vacuum and then cooling it in a vacuum or under a pressure of 100 to 200 atmospheres.
It is an alloy of aluminum, magnesium, copper, nickel, tin, etc.
Magnalium is an aluminum alloy with 5% magnesium and 95% aluminum with a small amount of Mg, Ni, sn, Fe, Mn, and Si.
It is mostly used in the aircraft and automobile industries.
It is also used in making ornamental fixtures.
So here you have to know all aspects related to alloy.
If you have any doubts then you are free to ask me by mail or on the contact us page.
Thank You.
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