(3 of 3)
Pure magnesium is soft and weak but alloyed with small amounts of aluminum (forming Dowmetal) its tensile strength and hardness increase six times. A bar of such a magnesium-base alloy is stronger than three times its weight in ordinary steel. It is not as strong as the same weight of an aluminum-base alloy (using .5% magnesium and 95% aluminum, making duralumin). Consequently airplane parts, where strength is important, are principally made of aluminum-base alloys, and Dowmetal is used primarily for engine castings, doors, hatches, floors, seats, brake assemblies, etc. Aluminum is usually used with some percentage of magnesium—partly for greater strength and partly because magnesium makes aluminum easier to work. Wherever strength is not essential the lighter magnesium gets the call.
After the war, cheap magnesium will compete in many markets which were closed to the more expensive metal of 1939. For example:
> White Sewing Machine Co. has made a portable machine weighing only 13 lb. as compared with 65 1b. for cast iron.
>Giant motor busses and trailers have been built in the U.S. with a deadweight saving of four to five tons through magnesium alloys.
> The European auto industry (before World War II) used thousands of tons of magnesium alloys in cars, though the U.S. industry has so far used little. Often this purpose was not so much to save dead weight as to give moving parts reduced inertia and centrifugal force, prevent vibration, fatigue, etc.
> Many fabricators would prefer a lightweight metal, if it is as cheap as magnesium promises to be, to any plastic.