Why use Alloys?

Why do we Alloy Metals?

 

One of the first alloys used by mankind was Bronze (1). Copper had been worked in the years preceding this by some cultures. However the softness of this metal meant that’s its uses beyond the decorative were very limited. Bronze, an alloy of copper and tin, was the answer.

An alloy is a mixture of two or more metals that together produce a mixture where the desired characteristics are improved (3). For example if tin and lead are alloyed, as we will demonstrate in our experiment, they produce an alloy that will scratch both of its constituents demonstrating its increased hardness.

Why are they harder?

The different types of atoms within an alloy disrupt the usual pattern of its structure. ‘Smaller’ atoms fit between the arrangements of ‘larger’ atoms to create a closely locking pattern (2). This makes it more difficult for the layers of atoms to slide over one another increasing hardness (2).

The change in the structure of metals also changes melting point, density and magnetism, corrosion resistance and many other characteristics. As such an Alloy can be tailor made to the exact specifications required for each use.

What else do we use Alloys for?

Alloys are all around us, we use them for thousands of different uses sometimes without even knowing it. Some examples of hidden alloys include.

• Silver jewellery. Think that necklace is pure silver? Unlikely, silver is extremely soft in its natural state, mixed with copper it becomes ‘Sterling silver’ (4).
• Everyone knows Airliners are made from Aluminium, but have you heard of Duralumin? Manganese, Magnesium and Copper combine with Aluminium to increase its strength, making you safer in the air (5)

Some Alloys have amazing properties. Nitinol, an alloy of Nickel and Titanium possesses the ability to be bent out of shape, only to return to its original shape when heated or an electrical current is passed through it. This makes it useful for things like reading glasses. Can you think of any more possible uses?

 

These Nitinol tubes are used by Doctors to keep your cardio vascular system working (6).

 Alloys have thousands of uses within our society, in fact many things would not be possible without them, try to imagine a world without satelites, computers, or even a stainless steel spoon.

Rob Jones

 

1: http://www.ancient.eu.com/Bronze_Age/

2: Http://www.bbc.co.uk/schools/gcsebitesize/science/

3: Concise oxford dictionary 1964.

4: http://www.buzzle.com/articles/types-of-alloys-and-their-uses.html

5: http://www.britannica.com/EBchecked/topic/174106/duralumin

6: http://www.saesgetters.com/applications/superelastic-medical-devices