DURALUMIN

a light alloy composed of 94 per cent aluminum with varying percentages of copper and magnesium. Its specific gravity ranges from 2.77 to 2.84, and it po e es the strength and hardne of mild steel. Its melting point is about 650° C and it can be rolled, forged and drawn when hot or cold. Its composition is modified, somewhat, according to the purpose for which it is req uired, and its properties can also be changed by heat treatment, so as to make it susceptible to rolling and drawing or to render it hard. The metal withstands atmospheric influences and is suitable for construction purposes where lightne combined with strength is required. It is commonly used for the framework of airships.