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...
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 ...
Molecular dynamics study of random and ordered metals and metal alloys
Kart, Hasan Hüseyin; Tomak, Mehmet; Department of Physics (2004)
The solid, liquid, and solidification properties of Pd, Ag pure metals and especially PdxAg1-x alloys are studied by using the molecular dynamics simulation. The effects of temperature and concentration on the physical properties of PdxÞAg1-x are analyzed. Sutton-Chen (SC) and Quantum Sutton-Chen (Q-SC) many-body potentials are used as interatomic interactions which enable one to investigate the thermodynamic, static, and dynamical properties of transition metals. The simulation results such as cohesive ene...
Mechanochemical and volume combustion synthesis of ZrB2
Akgun, Baris; ÇAMURLU, HASAN ERDEM; Topkaya, Yavuz Ali; SEVİNÇ, NACİ (Elsevier BV, 2011-09-01)
Formation of ZrB2 by volume combustion synthesis (VCS) and mechanochemical process (MCP) from ZrO2-Mg-B2O3 was studied. Production of ZrB2 by VCS in air occurred with the formation of side products, Zr2ON2 and Mg3B2O6 in addition to MgO and ZrB2. Zr2ON2 formation was prevented by conducting VCS experiments under argon. Wet ball milling was applied to the VCS products before leaching for easier removal of Mg3B2O6 phase. MgO and Mg3B2O6 were removed from wet ball-milled products by leaching in 5 M HCI for 2.5...
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.