Time filter

Source Type

Ostrowiec Świętokrzyski, Poland

Bilovol V.,University of Buenos Aires | Ferrari S.,University of Buenos Aires | Derewnicka D.,Institute of Precision Mechanics | Saccone F.D.,University of Buenos Aires
Materials Chemistry and Physics

Electronic structure of rapidly quenched ribbons of nominal composition NdyFe(86-y-x)B14Tix (x = 0, 2, 4; y = 7, 8 at.%) was studied by X-ray absorption (Fe and Ti K-edge) and X-ray photoelectron spectroscopy. It was found by XANES that Ti addition promotes modifications of the electronic structure of Fe sub-band. From the analysis of differences in the pre-edges structure areas, coming from variations in the 3d density of states near the Fermi level, the evidences of acceptor nature of Ti and Fe atoms in NdFeB alloys are present. Using photoelectron spectroscopy, we found that neodymium, iron and titanium are in both, metallic and oxidized, states on the surface of the ribbons. A higher Ti0 content (at high vacuum) is characteristic of the annealed samples. The presence of oxidized titanium states was corroborated by XANES. © 2014 Elsevier B.V. All rights reserved. Source

Nasilowska B.,Military University of Technology | Bogdanowicz Z.,Military University of Technology | Wojucki M.,Institute of Precision Mechanics
Journal of Constructional Steel Research

Here we investigated the effect of shot peening on the corrosion resistance of 904 L austenitic stainless steel joints made by CO2 laser beam and GTAW welding. Corrosion tests on the fusion zone in welds made by each of these welding methods were performed on shot peened and non-peened specimens. The samples were placed in a salt chamber and inspected after 24, 48, 72, 120, 240, 480, 720 and 1000 h. Pitting corrosion on non-peened welds made by GTAW welding was visible in the heat-affected zone from the face of the weld and reached a depth of 40 μm. Shot peening of welded joints decreased corrosion by 75%. In the case of shot peened welds made by laser beam welding, pitting corrosion had not occurred after 1000 h of salt mist exposure. © 2015 Published by Elsevier Ltd. Source

Spyra M.,Warsaw University of Technology | Derewnicka D.,Institute of Precision Mechanics | Leonowicz M.,Warsaw University of Technology
Physica Status Solidi (A) Applications and Materials Science

The effect of titanium addition on the structure and magnetic properties was studied for the nanocomposite Nd 7Fe 79-xB 14Ti x and Nd 8Fe 78-xB 14Ti x systems. The alloys were rapidly solidified by melt-spinning with the roll speed 20 m/s. The overquenched, amorphous ribbons were subsequently crystallization annealed for 20 min at 953-973 K. It was found that the addition of 2 and 4 at% of Ti leads to a substantial increase of the coercivity and maximum energy product of the nanocomposite magnets while maintaining the remanence unchanged. The highest properties were obtained for the alloys containing 4 at% of Ti. The maximum energy product of 143 kJ/ m 3 was achieved for the Nd 8Fe 74B 14Ti 4 alloy. The TEMstudies showed substantial differences in the morphology of the alloys. The ternary alloys contain grains of various sizes of approximately 300 nm. The alloys containing 4 at% of Ti exhibit more homogeneous structure with the crystal sizes up to 30 and 50 nm for the Nd 8Fe 74B 14Ti 4 and Nd 7Fe 75B 14Ti 4 alloys, respectively. More detailed information on the phase constitution was obtained from the Mössbauer spectroscopy. Comparison of the Ti-free and 4 at% Ti alloys revealed that the amount of the hard magnetic Nd 2Fe 14B phase decreases from 84.53 to 69.88% for the Nd 7Fe 79-xB 14Ti x system and increased from 66.60 to 82.48% for Nd 8Fe 78-xB 14Ti x system. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Bilovol V.,CONICET | Ferrari S.,CONICET | Pampillo L.G.,CONICET | Derewnicka D.,Institute of Precision Mechanics | And 2 more authors.
IEEE Transactions on Magnetics

The influence of Nb doping was studied on ribbons of nominal composition NdyFe86-x-yB14 Nbx (y = 7, 8; x = 0, 2, 4). The alloys were prepared by melt-spinning and then annealed at 973 K for 20 minutes. The magnetic characterization revealed that niobium addition improves substantially the magnetic properties of the studied alloys. The structural characterization showed that, in most alloys, the magnetically hard phase Nd2Fe14B precipitated as the main phase. This was not the case for the ternaries (x = 0) and for the Nd7Fe77 B14Nb2 alloys. Furthermore, the addition of Nb inhibited the precipitation of α-Fe, independently of the Nd content. From the complete set of samples studied in this work, we found that the sample with nominal composition Nd8 Fe74B14Nb4 exhibited the highest coercive field HC = 575 kA/m while Nd 7Fe75B14 Nb4 showed the highest maximum energy product, (BH)max = 73 kJ/m3. © 1965-2012 IEEE. Source

Babul T.,Institute of Precision Mechanics
Archives of Metallurgy and Materials

The article compared the results of theoretical calculations with results of actual temperature measurements of detonation sprayed NiCrBSi powder heated by the impact of the detonation products stream. Theoretical distributions of temperature in the powder particle were calculated by the Finite Element Method FEM, using the COSMOS/M program algorithm. In the absence of the heat transfer equations in the solid state being in movement, which is influenced by dynamic heat wave, the conduction mechanism described by Fourier's law was adopted. Experimental temperature measurements as a function of the acceleration path length were conducted using an own construction two-channel pyrometric system. The obtained data confirmed good agreement between the results obtained using FEM calculations method and results of experimental measurements using the pyrometric devices. Source

Discover hidden collaborations