When you mix copper and tin, you make bronze. No chemical reaction occurs. What is bronze?
Bronze is an alloy.
An alloy is a mixture of two or more metals created by melting down the metals, to make the metal ions free to move, and mixing the molten metal together, to bunch up all the different ions.
The structure of an alloy:
The dark and light grey dots represent two different metal ions that have been mixed together in a liquid state, then cooled to a solid state to fix the metal ion mixture in place and restrict movement of metal ions.
Creation of an alloy is not a chemical process as all that is happening is that heat is being applied to the metals to liquify them, then mixng them together.