Knowledge of materials have shaped the path of human history. In the past many discoveries have been accidental but have had huge consequences. One development, that had huge implications, was the use of Bronze alloys.
First of all what is Bronze? You may think of this as a colour. Bronze is actually an alloy of predominantly copper(~85%) with another element like tin, aluminium, manganese, nickel etc. The fact it is an alloy changes its properties and characteristics.
Brass is another alloy of copper, where zinc is added. This is a substitutional alloy as zinc can take place of copper in the crystal structure.
This is the picture of the micro structure of brass.
Copper alloys are harder and more durable than stone or pure copper. The difference in the size of the atoms disturbs the crystalline structure of the metal and prevents dislocations for moving through the material. Interestingly, tin is softer than copper but together they become harder.
Using the phrase ‘copper alloy’ is more useful historically as both bronze and brass had large importance. These alloys were first used thousands of years ago in the middle east. Copper alloys were used to make daggers, swords and arrow heads They were superior in battles as they could pierce armour of the time.
These stronger weapons allowed empires to expand and defeat enemies. As early bronze was made with arsenic, the fumes of its creation would be toxic. This led to demand for tin based alloys where fumes would not be toxic. In Europe in the past there were tin mines in Cornwall, England. It is thought one reason for the invasion of what is now Britian was in part to obtain tin for making bronze.
I’m aware this post is pretty short and bad. I realised iron is probably better to talk about in terms of historical importance.