1. Alloys
Noadswood Science, 2012

2. Alloys To know what alloys are, and how their properties are useful
Saturday, April 01, 2017
To know what alloys are, and how their properties are useful

3. Romans
Why were the Romans so successful at fighting?!

4. Romans
Apart from excellent tactics one clear advantage the Roman’s had over most of their enemies was technological excellence, specifically in their weapons
They originally used iron swords, but during the Republic period they advanced their manufacture – these new swords were still made from iron ores, but had bands of steel within their blades
The steels added superior strength and meant opposition soldiers often found their swords to be weaker, often shattering (leading to their death)!

5. Iron
Pure iron is soft and easily shaped because its atoms are arranged in a regular way that lets layers of atoms slide over each other
Pure iron is too soft for many uses
Layers of atoms slide over each other when metals are bent or stretched

6. Iron
Iron from the blast furnace is an alloy of about 96% iron with carbon and some other impurities – it is hard, but too brittle for most uses
So, most iron from the blast furnace is converted into steel by removing some of the carbon (adding just 1% impurities makes the iron much stronger)
Adding just 1% impurities makes
the iron much stronger

7. Steel
Carbon is removed by blowing oxygen into the molten metal – it reacts with the carbon producing carbon monoxide and carbon dioxide
These escape from the molten metal – enough oxygen is used to achieve steel with the desired carbon content
Other metals are often added, such as vanadium and chromium
There are many different types of steel, depending on the other elements mixed with the iron…

8. Resistant to corrosion
Steel
Type of steel
Iron alloyed with
Properties
Typical use
Low carbon steel
Around 0.25% carbon
Easily shaped
Car body panels
High carbon steel
Up to 2.5% carbon
Hard
Cutting tools
Stainless steel
Chromium and nickel
Resistant to corrosion
Cutlery and sinks

9. Making Steel
Different amounts of carbon (and other impurities) are added to make steel, stopping the atoms from sliding over one another as easily…
Strong
Strength
Hardness
Weak
0.5% 1% %
Amount of carbon added

10. Steel Steel with a low carbon content is easily shaped
Steel with a high carbon content is strong, but brittle
Stainless steel contains chronium and nickel

11. Alloys
Steel is an alloy – a mixture of two or more elements, where at least one element is a metal, is called an alloy
The properties of a metal are changed by including other elements, such as carbon
Alloys contain atoms of different sizes, which distort the regular arrangements of atoms making it more difficult for the layers to slide over each other, so alloys are harder than the pure metal
In alloys it is more difficult for the layers of atoms to slide over one another

12. Alloys
Copper, gold and aluminium are too soft for many uses, but they can be mixed with other metals to make them harder for everyday use…
Brass – used in electrical fittings is 70% copper and 30% zinc
18 carat gold – used in jewellery is 75% gold and 25% copper and other metals
Duralumin – used in aircraft manufacture is 96% aluminium and 4% copper and other metals

13. Smart Alloys
Smart alloys (shape memory alloy (SMAs)) can return to their original shape after being bent
They are useful for spectacle frames and dental braces (e.g. Nitinol)

14. Summary Questions
Complete the sentence below using the key words: aluminium; brass; bronze; smart; soft; and thousands
Copper has been used by people for ______ of years. Like pure iron, pure copper is too ______ to be very useful. Copper can be alloyed with tin to make ______, and with zinc to make ______.There are over 300 alloys of ______. Some alloys can ‘remember’ their shape when they are heated after they have been bent – they are called ______ alloys.
Explain the advantage of a dental brace made of a smart alloy over one made from a conventional alloy

15. Summary Questions
Copper has been used by people for thousands of years. Like pure iron, pure copper is too soft to be very useful. Copper can be alloyed with tin to make bronze, and with zinc to make brass. There are over 300 alloys of aluminium. Some alloys can ‘remember’ their shape when they are heated after they have been bent – they are called smart alloys.
The smart alloy can be cooled and shaped into the patient’s mouth. When the alloys warms up it will push the teeth into the correct position and hold them there!

16. Quiz