Topic
Tungsten
About: Tungsten is a research topic. Over the lifetime, 35225 publications have been published within this topic receiving 456213 citations. The topic is also known as: W & element 74.
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15 Apr 2001-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, gas tungsten arc (GTA) welds were performed on 4-mm thick plates, machined from as-cast magnesium AZ91D ingots, and the microstructure and defect formation was investigated by optical and scanning electron microscopy.
Abstract: Gas tungsten arc (GTA) welds were performed on 4-mm thick plates, machined from as-cast magnesium AZ91D ingots. The microstructure and defect formation was investigated by optical and scanning electron microscopy. Mechanical properties were determined by standard tensile tests on small-scale specimens. A wide heat affected zone (HAZ) (>3 mm) was created adjacent to the fusion line that consisted of two regions: (1) a partially melted zone (PMZ), created near the fusion line; and (2) a wide region, which was heat affected without melting. It was found that, after resolidification, a continuous Al12Mg17 phase existed along the PMZ grain boundaries that markedly reduced the joint strength to below that of fully annealed Mg-AZ91D alloys. In contrast, specimens machined from welded metal exhibited improved strength and ductility that resulted from the microstructural refinement caused by the rapid cooling during resolidification of the fusion zone. When the creation of a large PMZ was prevented, as in electron beam welding, the joint strength was comparable to that of the base metal.
165 citations
Patent•
04 Aug 2009
TL;DR: In this article, various methods of filling gaps or recessed features on substrates are provided, which involve bulk deposition of tungsten to partially fill the feature followed by a removing a top portion of the deposited tengsten.
Abstract: Methods of filling gaps or recessed features on substrates are provided. According to various embodiments, the methods involve bulk deposition of tungsten to partially fill the feature followed by a removing a top portion of the deposited tungsten. In particular embodiments, the top portion is removed by exposing the substrate to activated fluorine species. By selectively removing sharp and protruding peaks of the deposited tungsten grains, the removal operation polishes the tungsten along the feature sidewall. Multiple deposition-removal cycles can be used to close the feature. The filled feature is less prone to coring during CMP.
165 citations
TL;DR: In this article, three different tungsten alloys (pure W, a lanthanum-oxide dispersion strengthened W-alloy and a potassium doped Tungsten alloy) in different fabrication conditions (sintered and rolled rods) were tested to characterize their fracture behaviour at different temperatures (from −196 to 800 °C).
164 citations
TL;DR: In this article, the chemical state and thickness of tungsten oxide products were determined by ESCA, and it was found that the thickness of the oxide layer increases with increased humidity.
Abstract: Oxidation experiments were performed on pure tungsten and hot-pressed tungsten carbide. The chemical state and thickness of the oxide products were determined by ESCA. The oxidation of W and WC in dry atmosphere was performed in oxygen at temperatures ranging from 20 to 500 °C. The oxide formed is WO3. The thickness of the oxide layer increases slowly up to 200 °C, after which the oxide growth is rapid. The oxidation behaviour of W and WC in humid atmospheres was studied at room temperature in air at relative humidities of 60 and 95%. It was found that the thickness of the oxide layer increases with increased humidity. No formation of hydroxide was observed. Exposing W to water for one week results in a thick layer of WO2, WO3 and hydroxide. In the case of WC no oxide at all was visible after exposure to water. Furthermore, WC is resistant to further oxidation after exposure.
164 citations
TL;DR: In this article, the use of deux sequences spectroscopiques RMN a deux dimensions, of type COSY and INADEQUATE, was proposed to determiner sans ambiguite une attribution des liaisons tungstene-tungstenes dans les heteropolytungstates.
Abstract: Utilisation de deux sequences spectroscopiques RMN a deux dimensions, de type COSY, et INADEQUATE, pour determiner sans ambiguite une attribution des liaisons tungstene-tungstene dans les heteropolytungstates
164 citations