| Pure metals are rarely used in manufacturing because they are too soft. Usually, other elements are added to the molten metal so that the resulting solid is harder and has other desirable properties. An exception to this is is in the manufacture of car bodies which are made from new steels that are nearly pure iron. Adding larger ions
In the alloy, some of the added ions may be larger than most of the ions making up the metal lattice. They disrupt the regular arrangement of ions and make it more difficult for the layers to slide over each other. This makes the alloy harder and less malleable and ductile than the pure metal (in which the layers slip over each other more easily). Adding smaller atoms
Smaller sized atoms can also have a significant effect on the alloy structure. In steel, for example, atoms of non-metals such as carbon and nitrogen can fit into holes between the iron atoms. This also distorts the metal lattice and makes it more difficult for the layers to move over each other. | 
