In 1907, a low-nickel tungsten alloy was developed by machining, but the severe brittleness hampered its application. Until 1909, W. D. Coolidge from General Electric Co. prepared tungsten bar by powder metallurgy and produced tungsten filament with ductility at room temperature, which laid the foundation of tungsten processing and powder metallurgy.
However, this ductile tungsten alloy shows obvious brittleness after the bulb is ignited. In 1913, Pintsch invented thorium tungsten filament (ThO2 contains 1% ~ 2%), which greatly reduced the brittleness of incandescent filament. At first, the sag of the filament was not a problem because the filament was straight. But after 1913, Langmuir switched from straight to spiral so that the high working temperature and weight of the bulb caused the filament to sag. Therefore, both pure tungsten and thorium tungsten are difficult to meet the use requirements.
To solve the problems of droop of tungsten and short life, A. Pacz has developed a tungsten alloy that does not deform at high temperatures in 1917. At first, when he prepared pure tungsten, he used a refractory crucible to roast WO3. Unexpectedly, he found that the tungsten filament spiral made of the tungsten powder reduced by WO3 did not droop mysteriously after recrystallization. Then, after 218 times of repeated experiments, he finally found that silicate containing potassium and sodium was added to WO3•H2O, and the tungsten filament made by reduction, pressing, sintering and processing was recrystallized to form a rather coarse grain structure that is neither soft nor anti-droop. This is the earliest non-drooping tungsten filament. Pacz's discovery laid the foundation for the production of non-drooping tungsten wire, which is still called "218 Tungsten Wire" in the United States to commemorate this important discovery.
At present, various types of tungsten alloys are made for use in all walks of life in modern industry.
Mo-W alloy
Molybdenum tungsten alloy is an alloy containing molybdenum and tungsten elements, it includes molybdenum based molybdenum alloy and tungsten-based molybdenum alloy series. The alloy can be formed in any proportion and is a completely solid solution alloy at all temperatures.
Niobium tungsten alloy
Niobium tungsten alloy is a niobium alloy formed by adding a certain amount of tungsten and other elements. Tungsten is an effective strengthening element of niobium, but with the increase of the amount of tungsten, the plastic-brittle transition temperature of the alloy will rise and the grain will grow significantly. Therefore, to obtain high strength niobium tungsten alloy, the amount of tungsten should be controlled appropriately, and the elements such as zirconium and hafnium should be added in appropriate amounts to refine grains and reduce the temperature of plastic-brittle transition.
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