The Collaborative International Dictionary of English v.0.48:

Duralumin \Duralumin\ prop. n. [a trademark.]
   an aluminum-based alloy which is both light and strong,
   containing 4 per cent of copper and 0.5 per cent of magnesium
   and smaller amounts of iron, manganese, and silicon. It
   hardens with aging at room temperature.
   [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

Duralumin
    n 1: an aluminum-based alloy