Alloys of Tungsten

Tungsten enters into the composition of many useful alloys. Aluminium and tungsten readily unite. Several alloys, the percentage compositions of which correspond to the possible formulae Al₇W, Al₅W, Al₄W, Al₃W, and AlW₂, have been described. The alloy corresponding to the formula Al₅W forms large, thin, monoclinic crystals and is readily attacked by aqua regia, whereas that corresponding to the formula Al₇W forms hexagonal crystals which are insoluble in aqua regia and only sparingly attacked by a fused mixture of alkali carbonate and nitrate.

The preparation of alloys with chromium in all proportions has been described, together with that of alloys with chromium and iron and with chromium, copper, and iron. An alloy resembling stellite, but containing 20 per cent, tungsten, 15 per cent, chromium, and 65 per cent, cobalt, is very hard and is used for cutting tools and for surgical instruments, since it is unaffected by organic acids or ordinary antiseptics. A similar alloy, also used for the latter purpose, is known as amaloy and contains tungsten, chromium, and nickel. Certain alloys with copper and nickel are highly resistant to concentrated mineral acids and are used as substitutes for platinum.

An alloy of tungsten with gold has been described, as also have alloys of tungsten with copper and with lead.

Tungsten and antimony are stated to unite, but tungsten and bismuth probably do not alloy.

Alloys of tungsten with other elements are described in other volumes in this series.