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Naturally occurring tungsten consists of four stable isotopes (182 W, 183 W, 184 W, and 186 W) and one very long-lived radioisotope, 180 W. Theoretically, all five can decay into isotopes of element 72 by alpha emission, but only 180 W has been observed to do so, with a half-life of (1.8 ± 0.2) × 10 18 years; [36] [37] on average, this yields ...
Wolframite is highly valued as the main source of the metal tungsten, a strong and very dense material with a high melting temperature used for electric filaments and armor-piercing ammunition, as well as hard tungsten carbide machine tools. During World War II, wolframite mines were a strategic asset, due to its use in munitions and tools. [13]
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Tungsten steel is any steel that has tungsten as its alloying element with characteristics derived mostly from the presence of this element (as opposed to any other element in the alloy). Common alloys have between 2% and 18% tungsten by weight along with small amounts of molybdenum and vanadium which together create an alloy with exceptional ...
For the production of the tungsten heavy alloy, binder mixtures of nickel and iron or nickel and copper are widely used. The tungsten content of the alloy is normally above 90%. The diffusion of the binder elements into the tungsten grains is low even at the sintering temperatures and therefore the interior of the grains are pure tungsten. [18]
The discovery of superhard tungsten tetraboride is further evidence for the promising design approach of covalently bonding incompressible transition metals with boron. While WB 4 was first synthesized and identified as the highest boride of tungsten in 1966, [52] it was only recognized as an inexpensive superhard material in 2011. [53]
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Tungsten was used in hammer throw balls at least up to 1980; the minimum size of the ball was increased in 1981 to eliminate the need for what was, at that time, an expensive metal (triple the cost of other hammers) not generally available in all countries. [135] Tungsten hammers were so dense that they penetrated too deeply into the turf. [136]