Alloys + Properties

What is an alloy?

A mixture of a metal with other elements, often including other metals.

Why are alloys made?

To obtain properties more suitable for particular uses.

Why are pure metals often soft?

Their atoms are arranged in regular layers that can slide over one another.

Why are alloys generally harder than pure metals?

Different-sized atoms distort the regular arrangement and make layers harder to slide.

What is steel?

An alloy of iron and carbon, sometimes containing other elements.

Why is carbon added to iron to make steel?

It generally increases hardness and strength.

What is low-carbon steel?

Steel containing a relatively small proportion of carbon.

What are the properties of low-carbon steel?

It is generally more easily shaped and less brittle than high-carbon steel.

What is high-carbon steel?

Steel containing a higher proportion of carbon.

What are the properties of high-carbon steel?

It is generally harder but more brittle.

What is stainless steel?

Steel containing chromium, often with nickel and other elements.

Why is stainless steel resistant to corrosion?

Chromium forms a protective oxide layer.

What is brass?

An alloy of copper and zinc.

What is bronze?

An alloy of copper and tin.

What is an aluminium alloy?

Aluminium mixed with other elements to improve properties such as strength.

Why are aluminium alloys useful in aircraft?

They can combine low density with improved strength.

Why is gold alloyed for jewellery?

Pure gold is relatively soft, and alloying improves its durability.

Why are different alloys used for different applications?

They have different combinations of hardness, strength, corrosion resistance and other properties.