Search results for "MAGNESIUM"
showing 10 items of 490 documents
The Annealing Behavior of the Subsurface Zone Induced by Friction in Bismuth Detected by Positron Lifetime Technique
2013
The annealing behavior of the subsurface zone (SZ) in pure bismuth induced by dry sliding was studied using the positron lifetime measurement. This measurement allows us to detect the SZ and its recovery, and recrystallization processes. The comparative measurements of the sample exposed to compression revealed the thermal stability of the SZ. The compressed sample rebuilt its structure due to the recovery and recrystallization processes at the temperature of 60 °C, whereas the sample exposed to dry sliding does it at higher temperature of 260 °C, which is close to the melting point. The isothermal annealing at the temperature of 100 °C confirmed these results. The defect depth profile indu…
Aggregative behavior of cohesive magnesium carbonate powders during fluidization and aerated discharge
2014
In this paper we studied the aerated discharge of two magnesium carbonate powders differing in their average diameter and particle size distribution. These samples were characterized by means of fluidization experiments and rheology shear tests carried out in a rotating shear cell. In the hopper discharge experiments, besides the discharge rates and the mass of residual solids as a function of the aeration rate, the aggregative behavior was observed by means of photographic techniques. Solids aggregates were actually visible within the aerated beds of solids during the fluidization experiments and in the streams of the discharging solids. Experimental data on the powder flow properties and …
Influence of magnesium content on the corrosion resistance of the cut-edges of Zn–Mg-coated steel
2015
Abstract The ability of Zn–Mg coatings (with magnesium content between 5.8 and 15.5 wt.%) to protect steel sheets has been evaluated with local electrochemical techniques (scanning vibrating electrode technique, microcapillary electrochemical cell) and rotating disk electrode, and compared with the corrosion protection afforded by a pure zinc coating. From immersion tests of coated steel cut-edges, it is observed that alloying zinc with magnesium leads to a decrease of the galvanic current between the coating and the steel surface, and to an improvement of the steel corrosion resistance after a drying period, due to the presence of magnesium in the corrosion products.
Process Mechanics in Friction Stir Welding of Magnesium Alloys: Experimental and Numerical Analysis
2012
Light weight construction is a major task within automotive and aircraft industry due to lower fuel consumption or increase the possible payload. Structural or exterior shell components are more and more manufactured out of aluminum alloys for this reason. A further weight reduction could be achieved by the substitution of aluminum alloys by magnesium alloys. Also the application of blanks with a varying thickness is a possibility to realize light weight design. To combine the advantages of weight reduction by the use of magnesium alloys and tailored welded blanks (TWBs), an effective joining technique is required. Friction Stir Welding can be used for difficult to be welded magnesium alloy…
The Effect of Technological Factors on the Synthesis of PbMg 1/3 Nb 2/3 O 3
2003
Conventional technique of solid phase reactions allows one to obtain PbMg 1/3 Nb 2/3 O 3 material with about 20 vol.% of the pyrochlore phase. The latter can be reduced to 5 vol.% by Swartz-Shrout two-stage solid state reaction via MgNb 2 O 6 having the columbite structure. A single-phase perovskite product can be obtained by by the two-stage columbite method from mixtures containing 0.2 mol. parts of overstoichiometric MgO. The best results are obtained by using magnesium carbonate hydroxide pentahydrate (MgCO 3 ) 4 ·Mg(OH) 2 ·5H 2 O as the magnesium source. The modified route yields stoichiometric single-phase PMN.
Formability of Friction Stir Welded AZ31 Magnesium Alloy Sheets
2010
The formability of friction stir welded AZ31 magnesium alloy sheets was investigated by means of uniaxial tensile and hemispherical punch tests performed under different process conditions. The results of the tensile tests were analysed in terms of flow stress and ductility at different temperature and strain rate; the hemispherical punch tests, carried out at different temperatures, provided the limiting dome height. The formability of FSW-ed blanks was compared to the one exhibited by the base material in order to evaluate the quality of the welded joints.
Tool Geometry in Friction Stir Welding of Magnesium Alloy Sheets
2009
Friction Stir Welding (FSW) has been arousing a continuously increasing interest among joining processes since its invention in 1991. Although mainly used for aluminum alloys, it can also be applied to other light alloys. In the present work, experimental and numerical campaigns have been performed with the aim to study the effect of the tool geometry on the mechanical properties of FSW-ed AZ31 magnesium alloy sheets. The results, presented in terms of tensile strength, ductility, micro-hardness values and numerical field variables distributions, allow to reach a deeper knowledge on the behaviour of such relatively new material when FSW-ed, and can be used for a full optimization of the joi…
Frequency dependence of the microwave surface resistance of MgB2 by coaxial cavity resonator
2014
Abstract We report on the microwave (mw) properties of a cylindrical MgB2 rod prepared by the reactive liquid Mg infiltration technology. The MgB2 rod, 94.3 mm long, is used as inner conductor of a coaxial cavity having a Cu tube as external conductor. By analyzing the resonance curves of the cavity in the different resonant modes and at different temperatures, we have determined the temperature dependence of the mw surface resistance, R s , of the MgB2 material, at fixed frequencies, and the frequency dependence of R s , at fixed temperatures. Our results show that the R s ( f ) curves follow a f n law, where n decreases on increasing the temperature, starting from n ≈ 2 , at T = 4.2 K , d…
<title>Raman scattering by phonons and magnons in Ni<formula><inf><roman>c</roman></inf></formula>Mg<for…
2003
ABSTRACT The Raman scattering by phonons and magnons was studied at room temperature in polycrystalline solid solutions NiMg1O and pure NiO. The experimental Raman spectrum of NiO consists of six well resolved bands, whose originis due to the disorder-induced one-phonon scattering (bands at 400 and 500 cm'), two-phonon scattering (bands at 750,900 and 1 100 cm) and two-magnon scattering (band at 1500 cm). In NiMg1O solid solutions, a relative increase ofone-phonon scattering is observed upon a dilution of nickel oxide by magnesium ions: at room temperature, the two-magnon band becomes invisible for c<O.7, whereas the two-phonon contribution disappears at c<O.5. Such behaviour isexplained by…
Structure and Phase Changes in Natural and Synthetic Magnesium Aluminum Spinel
2015
Natural spinel crystals from Ural and Pamir deposits and synthetic magnesium aluminium spinel single crystals with different stoichiometry (MgO.nAl2O3 ) grown by Verneuil method were used. The photoluminescence (PL), its excitation (PLE) and optical absorption of stoichiometric and nonstoichiometric magnesium aluminium spinel crystals containing the chromium and manganese ions and defects produced by fast neutron irradiation( fluence up to 1020cm-2, E&gt;0.1 MeV) are investigated. The broadening of R- and N-lines takes place in synthetic stoichiometric spinel. Structure of synthetic nonstoichiometric spinels (n&gt;1) has to be more disordered, since in addition to the site exchange …