An alloy is a just a blend of metals. It may be harder or softer than one of the pure metals, but the results aren't always obvious or predictable.
So a common alloys is gold and silver mix for jewellery. But have you made the gold harder by adding silver? Or made the silver softer by adding gold?
Also, adding a weaker metal to an alloy may make the resulting alloy stronger then either original metal. ~5% Aluminium added to Titanium actually creates an alloy stronger than pure Titanium, even though aluminium is weaker.