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What is an alloy?

An alloy is a metallic substance formed by mixing at least one metal with one or more metals or non-metallic elements. Alloys are typical examples of solid solutions, in which the metal in the highest proportion acts as the solvent and the other components as solutes.

Alloys have been known for centuries. The first alloys discovered and used were brass and bronze. The first is a mixture of copper and zinc, while the second is made up of copper and tin.

Today, alloys can be found everywhere. From the structural tubes that form the skeleton of modern buildings, to the most advanced aircraft and spacecraft.

Alloy properties

Here are some important properties of alloys, along with some examples.

Melting point

Most metals are characterized by high melting points, and the same applies to the vast majority of alloys. However, there are some particular alloys that have much lower melting points than even any of their components alone. This is the case with fusible or low-melting alloys.

Some even have melting points so low that they are liquid at room temperature.

Electric conductivity

Like the metals that compose them, alloys have good electrical conductivity.

Thermal conductivity

Being made up mainly of metals, alloys also have good thermal conductivity.

Ductility

Ductility is another property that can be adjusted to taste through alloys. This property refers to the ability to transform a material into threads or wires without breaking. Many alloys have better ductility than separate metals.

Resistance to corrosion

The corrosion resistance of stainless steels and other alloys is one of their most important characteristics. This is especially useful for applications where the material is exposed to the environment or corrosive substances.

Tenacity

Toughness is the ability of a material to absorb impacts without breaking. Many alloys used to manufacture tool parts such as drill bits, hammers and nails have high toughness.

Hardness

Many pure metals are quite soft, but some of their alloys can be formulated to obtain materials with impressive hardnesses. Tungsten carbide alloys are a good example of extremely hard alloys.

Types of alloys

Alloys can be classified according to the number of components of which they are formed and also according to the type of elements of which they are composed.

According to the number of components:

  • Binary alloys – These are made up of just two components. One is the base metal that acts as a solid solvent, while the other is called an alloying agent.
  • Ternary alloys: are those that contain three components, that is, a base metal and two alloying components.
  • Quaternary alloys: as their name implies, these are made up of four components: a base metal and three alloys.
  • Complex alloys – All other alloys that contain more than five components are called complex alloys.

According to the type of components:

Depending on the class of metals that make them up, alloys can be ferrous or non-ferrous:

  • Ferrous alloys: are those that contain iron as a metal or main component. Ferrous alloys, in turn, are divided into carbon steels and steel alloys.
  • Non-ferrous alloys: these are the alloys that do not contain iron in any proportion. The fusible alloys that we mentioned above are normally non-ferrous alloys.

Examples of alloys

1. Tool steel

It is a ferrous alloy that has been used for decades to make tools or tool parts that must withstand many forces and friction.

2. Brass

This is an alloy between copper and zinc. This alloy has a pleasant golden color and is highly resistant to corrosion, even in the presence of salts, which is why it is widely used in taps and metal parts for boats.

3. White gold

It is a mixture of gold, zinc, copper and nickel that is often used as a less expensive substitute for pure gold in jewelry making.

4. Wood’s metal

This is a quaternary alloy that contains bismuth as the base metal and lead, tin, and cadmium as alloys. It is an alloy that melts at 70ºC so it is used in welding, also as fuse valves in fire safety systems and more.

5. Bronze

It is one of the oldest alloys. It is made up of copper and tin in different proportions. It has a slightly redder color than brass and is widely used in the manufacture of musical instruments, ornamental pieces and sculptures.

6. High speed steel (HSS)

This is an improved version of tool steel that contains alloys with tungsten, molybdenum, chromium, vanadium, and cobalt. They are extremely hard alloys that are often used in cutting bits and saws.

7. Electro

It is a natural binary alloy between gold and silver that was used very frequently in the manufacture of coins.

8. Ferrovanadium

It is an alloy of iron with vanadium that is very hard and highly resistant to corrosion. Despite its hardness, it is a very fragile material that tends to be ground into a fine powder that is added to other alloys as an alloying agent.

9. Pewter

This is an example of a quaternary alloy made up of tin, copper, lead, and antimony. It was used to make tableware and food containers.

10. Ferroaluminum

Ferroaluminum is a type of alloy that contains iron and 40-60% aluminum. This alloy is characterized by its resistance to tension, its hardness and by maintaining its strength at high temperatures.

11. Galinstano

It is a fusible alloy that melts at -19ºC. It is used in many applications mainly as a replacement for mercury in thermometers and in thermal baths.

12. SG iron

Also called spheroidal graphite iron. It is a type of alloy that contains small pearls (spheres) of graphite, which makes it more fluid when molten. It is widely used in the manufacture of molded parts.

13. Rose Metal

This is another example of fusible alloys that are used as low melting point solders.

14. Duralumin

It contains aluminum as the main element and magnesium, manganese, silicon and copper as alloys that provide superior hardness without compromising the lightness that characterizes aluminum.

15. Ferrotitanium

It is an alloy between iron and titanium that contains between 15% and 45% titanium. It is widely used as an alloying agent for the manufacture of different types of steel.

16. Stainless steel

It is an iron alloy with varying amounts of carbon and at least 10.5% chromium. It is a fairly hard material, very shiny and very resistant to corrosion.

17. Amalgam

Used for years by dentists as a wedge for teeth, this alloy is formed by dissolving metals such as copper, gold, zinc, and tin in liquid mercury.

18. Magnalium

This is a very light, hard and strong alloy formed between magnesium and aluminum that is often used in the manufacture of luxury automotive wheels.

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