# What makes some aluminium alloys so strong while remaining light?

Compared to cast iron, for example, certain alloys of aluminum have both strength and weight advantages. How can aluminum be so strong while being so light?

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Can you be more specific on the question. Each metal has its straights and weaknesses. –  Fortunato Jun 29 '11 at 22:04
Diamond is also very light and stronger than Aluminum. Lead is very heavy and soft. There is no connection between strength and density. –  fffred Aug 9 '13 at 23:27

However, aluminum is MUCH lighter (less dense) than steel: $2.8g/cm^3$ for Al as opposed to $7.8g/cm^3$ for steel, making Al a clear winner in the strength/weight arena.