The composition of gun metal bronze is given below:īy substituting some of the copper atoms for tin in the lattice, we make an alloy, bronze, which is harder than copper and has a lower density and melting point than copper which makes it easier to cast. In the bronze solid solution, copper is the solvent and tin is the solute.īronze is an alloy made up of 70-90% copper and 30-10% tin.
In the diagram on the right, copper atoms are represented by the black circles while the red circles represent atoms of tin which have substituted for some of the copper atoms. This means that the volume of space occupied by an atom of tin is also slightly more (1.5 times) more than the volume of space occupied by an atom of copperīecause atoms of tin and copper are of a similar size, tin atoms can substitute for some of the copper atoms in the metal lattice. In other words, every 100 g of carbon steel contains 1 g of carbon and 99 g of iron.įrom the table we can see that the radius of an atom of tin is 1.15 times the radius of an atom of copper, that is, the radius of an atom of tin is only slightly larger than the radius of an atom of copper. In the carbon steel solid solution, iron is the solvent and carbon is the solute.Ĭarbon steel is made by adding about 1% by mass of carbon to iron.
The carbon atoms are referred to as interstitial atoms, in this case, interstitial carbon atoms, and are shown as red circles in the diagram on the right with the iron atoms shown as the larger black circles. Since an atom of carbon is much smaller than an atom of iron, carbon atoms can occupy the "holes", the interstices, in the lattice of iron atoms.
This means that the volume of space occupied by a carbon atom is only 20% of the volume of space occupied by an atom of iron. The radius of a carbon atom is only 60% that of an iron atom, that is, the radius of a carbon atom is just a bit more than half the radius of an iron atom.