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Engineering Materials...What 'stuff' is made from

Engineering can be defined as the application of science and technology to create or produce something of use.


In order to ‘produce’ something, we need to process or 'form' some sort of material into a useful ‘shape’ or combination of shapes. In order to do this, we need to understand what materials are, and how they can be processed and shaped.

Broadly speaking, engineering materials can be broken down into 4 distinct groups.

  • Metals

  • Polymers

  • Ceramics

  • Composites


Metals

Metals are the largest group of materials, and are involved in the majority of engineering applications. Metals can be subdivided into two major families, ferrous and non-ferrous. Ferrous simply means that the material ’contains iron’, so a ferrous metal is one which contains iron in some way, whilst a non-ferrous metal does not.


The primary bonding method between metals is metallic bonding, and the structural arrangement of most metals can be grouped within one of several crystalline structures.




Example of a Ferrous Metals


Steel

At its most fundamental, steel is an alloy of iron and carbon. There are many different grades of steel depending on the levels of carbon added to the iron (it typically ranges from 0.3% up to 1.5%).


Additionally alloying other elements such as chromium, nickel or titanium can be used to manufacture steel with a range of properties, such as increased strength, or durability but without increasing its weight.


In general, increasing the levels of carbon added, subsequently increases the steels strength and hardness, whilst decreasing its ductility.



Examples of Non-Ferrous Metals


Aluminium Alloys

Pure aluminium is relatively weak and soft, not much use as an engineering material! However once it is mixed with other materials (i.e. an alloy) you can then start to increase its strength. The pure aluminium does have good corrosion resistance due to an oxide coating that forms over the material and prevents oxidation, this is a positive property that the aluminium brings, but you must be careful as alloying the aluminium tends to reduce its corrosion resistance.


Aluminium is a widely used material and particularly in the aerospace industry due to its light weight and corrosion resistance. Although aluminium alloys are generally not as strong as steels, they have a very good strength-to-weight ratio (in fact they will often exceed steel in a strength-to-weight ratio). Perfect for making large components such as aircraft wings or fuselages.


Titanium Alloys

Titanium alloys are light, strong, and have high corrosion resistance. Their density is much lower than steel, and their strength-to-weight ratio is excellent. In fact, Titanium has an excellent mixture of high strength, stiffness, toughness, lightness, and resistance to corrosion over a range of temperatures makes it an excellent choice for many aerospace structures.


Of course there is a downside! And that is the relatively high cost of titanium alloys compared to other materials.


Polymers

The term 'polymer' encompasses a vast range of biological and synthetic materials that are used in a wide range of applications. The market for polymers involves many large commercial organisations that compete with one another in different market sectors.