3.4 Alloys
An alloy is a mixture of two elements, one of which is a metal. An alloy will often have different properties to the metals that they contain. Alloys are used because by adding another element, they become more useful. Iron that has come straight out of the blast furnace (cast iron) is only 96% iron. The other 4% is made up of impurities, which are mainly carbon. The impurities in cast iron make it brittle, meaning that cast iron has limited uses.
When all the impurities are removed from cast iron out of the blast furnace, the atoms in pure iron have a regular arrangement. This regular arrangement of atoms makes it easy for atoms to slide over each other, making cast iron easy to shape and bend. Pure iron is too bendy for most uses.
Most irons are converted into steel by adding other elements to pure iron. By adding other elements, steel has some more desirable properties. Carbon or other elements like chromium or nickel can be added to steel. We have a few different types of steel that are used for different purposes, such as:
Many metals that we use in our everyday lives are alloys. This is because by using a pure version of a metal it would be too soft for many uses and adding another element makes the metal stronger for everyday use and has the desired properties. For example, copper, gold, iron and aluminium are too soft for everyday uses. Copper can be mixed with nickel to create cupronickel, which is hard and corrosion resistant. It can also be mixed with tin to make bronze, which is harder than pure copper. Gold can have zinc, copper, nickel or any other substance added to it to make it harder.
The reason why adding another substance into the metal makes the alloy stronger than just the pure metal is because the added elements have different sized atoms that distort the regular arrangement of atoms (that would be seen in the pure substance). This distortion in regular layers makes it harder for the atoms to slide across each other, thus making the alloy harder than the pure metal.
We can also have smart alloys, such as nitinol, which is an alloy of nickel and titanium. Nitinol is able to be bent out of shape but when heat is applied or an electric current passed through it, nitinol will return back to its original shape. Scientists now have a better understanding about the properties of metals and are now able to design alloys with specific uses in mind. In the past scientists tended to use trial and error to come up with new alloys.
When all the impurities are removed from cast iron out of the blast furnace, the atoms in pure iron have a regular arrangement. This regular arrangement of atoms makes it easy for atoms to slide over each other, making cast iron easy to shape and bend. Pure iron is too bendy for most uses.
Most irons are converted into steel by adding other elements to pure iron. By adding other elements, steel has some more desirable properties. Carbon or other elements like chromium or nickel can be added to steel. We have a few different types of steel that are used for different purposes, such as:
- Low carbon steel (0.1% carbon) – Used in car bodies as it is easy to make into any shape
- High carbon steel (1.5% carbon) – Used in builds, bridges as it is very hard, strong and inflexible
- Stainless steel (chromium or nickel added) – Used in cutlery because of its corrosion-resistant properties
Many metals that we use in our everyday lives are alloys. This is because by using a pure version of a metal it would be too soft for many uses and adding another element makes the metal stronger for everyday use and has the desired properties. For example, copper, gold, iron and aluminium are too soft for everyday uses. Copper can be mixed with nickel to create cupronickel, which is hard and corrosion resistant. It can also be mixed with tin to make bronze, which is harder than pure copper. Gold can have zinc, copper, nickel or any other substance added to it to make it harder.
The reason why adding another substance into the metal makes the alloy stronger than just the pure metal is because the added elements have different sized atoms that distort the regular arrangement of atoms (that would be seen in the pure substance). This distortion in regular layers makes it harder for the atoms to slide across each other, thus making the alloy harder than the pure metal.
We can also have smart alloys, such as nitinol, which is an alloy of nickel and titanium. Nitinol is able to be bent out of shape but when heat is applied or an electric current passed through it, nitinol will return back to its original shape. Scientists now have a better understanding about the properties of metals and are now able to design alloys with specific uses in mind. In the past scientists tended to use trial and error to come up with new alloys.