Effects of fabrication method on initial powder characteristics and liquid phase sintering behaviour of tungsten

2018-12-01
Erol, Mahmut
Erdogan, Metehan
Karakaya, İshak
Direct electrochemical production of tungsten involves removal of oxygen in solid state from an important tungsten compound, calcium tungstate, in molten salts. A detailed experimental study was performed to characterize the liquid phase sintering behaviour of the tungsten powder (WE), which was produced by the direct electrochemical reduction technique. All of the tungsten heavy alloy (WHA) compositions covered in this study, contained four parts nickel, one part cobalt and over 90 wt% tungsten. The pellets were sintered at 1500 and 1550 degrees C under continuous flow of an equimolar hydrogen-argon gas mixture. A commercially available tungsten powder (W-C) was also used to prepare the same tungsten heavy alloy compositions as those prepared by the electrochemically produced tungsten powder to act as a control group. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF) and hardness measurements were employed for characterization. The analyses provided that; the tungsten powder as obtained from the direct electrochemical reduction process contained some unreduced CaWO4 particles and they limited the grain growth and mass transport in the liquid phase. Although calculated relative densities were a bit lower than desired, the tungsten heavy alloys produced by the electrochemical reduction technique was promising for use when average grain size, dissolved tungsten contents and general/matrix hardness values are considered.
INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS

Suggestions

Effect of swaging on microstructure and tensile properties of W-Ni-Fe alloys
DURLU, NURİ; Caliskan, N. Kaan; Bor, Sakir (Elsevier BV, 2014-01-01)
The objective of this study was to investigate the effect of swaging on the microstructure and tensile properties of high density two phase alloys 90W-7Ni-3Fe and 93W-4.9Ni-2.1Fe. Samples were liquid phase sintered under hydrogen and argon at 1480 degrees C for 30 min and then 15% cold rotary swaged. Measurement of microstructural parameters in the sintered and swaged samples showed that swaging slightly increased tungsten grain size in the longitudinal direction and slightly decreased tungsten grain size i...
Effects of synthesis, doping methods and metal content on thermoluminescence glow curves of lithium tetraborate
Kayhan, Mehmet; Yılmaz, Ayşen (Elsevier BV, 2011-07-28)
Lithium tetraborate: Li(2)B(4)O(7), (LTB) has been synthesized and doped with various Mn content by different methods, such as, high temperature solid state synthesis and solution assisted synthesis methods. Powder XRD results proved the formation of solid-solution by replacing Mn with Li ions in LTB lattice at lower amount of Mn doping, for example 0.1-3.0% Mn doping. In this research TL glow curves of Mn doped lithium tetraborate (LTB: Mn) produced by using different synthesis and doping methods and the e...
Effect of process parameters on mechanical properties of high pressure die cast magnesium AZ91 components
Okcu, Işık Yılmaz; Kalkanlı, Ali; Department of Metallurgical and Materials Engineering (2011)
Before beginning the experimental work of this study, a magnesium high pressure die casting facility is set up to manufacture magnesium cast parts for defence industry. In this thesis two components are cold chamber high pressure die casted using magnesium alloy AZ91 as raw material, and one component was manufactured using both aluminium alloy A.413, and magnesium alloy AZ91. Mechanical properties of high pressure die casting parts depend on various parameters such as, thickness of the cast part, position ...
Effect of Au on the crystallization of germanium thin films by electron-beam evaporation
EYGİ, ZEYNEP DENİZ; KULAKCI, MUSTAFA; Turan, Raşit (2014-11-01)
Metal induced crystallization is a widely used method to form crystalline/polycrystalline structures at low temperatures. In this work, Au was applied to enhance the crystallization of amorphous Ge films. Ge films with thicknesses of similar to 1.5 mu m were fabricated by electron beam evaporation on c-Si substrate with and without very thin Au layer. Crystallization properties of Ge films were analyzed for different growth and post annealing temperatures varied between 270 degrees C and 730 degrees C. The ...
Effect of lithium doping on the properties of Tl-based superconductors
Kayed, TS; Ozkan, H; Hasanlı, Nızamı (IOP Publishing, 2001-09-01)
The effects of lithium doping on the formation and properties of the T1-based superconductors have been studied. Lithium atoms up to around 3 mol.% have been added to the oxides of nominal composition Tl1.8Ba2Ca2.2Cu3Ox, and the usual solid-state reaction method has been applied. Lithium additions in the range 0.23-0.29 mol.% increase the fraction of the Tl-2223 phase and significantly improve the critical temperature of the samples. Higher amounts of lithium additions diminish the Tl-2223 phase, reduce the...
Citation Formats
M. Erol, M. Erdogan, and İ. Karakaya, “Effects of fabrication method on initial powder characteristics and liquid phase sintering behaviour of tungsten,” INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS, pp. 82–89, 2018, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/41985.