Papers by Luzinete Barbosa
Materials Science Forum, Sep 1, 2018
Pre-sintering for removal of lubricants is one of the most important steps in processing of powde... more Pre-sintering for removal of lubricants is one of the most important steps in processing of powder metallurgy materials to achieve corrosion resistance. This is often the most neglected step in the sintering process. Incomplete removal of these organic compounds may result in sensitization of sintered parts. The aim of this study is to investigate the effect of lubricant removal process on the corrosion resistance of sintered AISI 304 L stainless steel filters. Pre-sintering was carried out at 450° C and sintering at 1150° C. As lubricant, 1% wax was used. The corrosion resistance of sintered samples was evaluated by polarization and tests, optical and scanning electron microscopy. The results showed that lubricant removal was not complete and during sintering sensitization of the stainless steel occurred decreasing the localized corrosion resistance of the stainless steel.
Recycling process viability from zirconium alloys scraps of lathe melted in the vacuum arc remelt... more Recycling process viability from zirconium alloys scraps of lathe melted in the vacuum arc remelting (VAR) furnace Reis, L.A.M.(1); Alencar, M.C.(1); Gomes, M.P.(1); Pereira, L.A.T.(1); Barbosa, L.P.(1); Mucsi, C.S.(1); Rossi, J.L.(1); Instituto de Pesquisas Energéticas e Nucleares(1); Instituto de Pesquisas Energéticas e Nucleares(2); Instituto de Pesquisas Energéticas e Nucleares(3); Instituto de Pesquisas Energéticas e Nucleares(4); Instituto de Pesquisas Energéticas e Nucleares(5); Instituto de Pesquisas Energéticas e Nucleares(6); Instituto de Pesquisas Energéticas e Nucleares(7);
SAE Technical Paper Series, 2018
Materials Science Forum, 2012
In this work, the effect of sintering atmosphere on the corrosion resistance of sintered titanium... more In this work, the effect of sintering atmosphere on the corrosion resistance of sintered titanium has been evaluated in 0.9 % aqueous NaCl solution to simulate physiological environment. Corrosion tests were performed on titanium porous sintered under vacuum and vacuum plus dynamic argon. The results showed better passive properties associated to the titanium sintered under argon plus vacuum atmosphere than to the vacuum sintered titanium. The better corrosion resistance of the argon plus vacuum sintered titanium was attributed to the formation of a thin passive film on the titanium surface during sintering due the low oxygen content present in this atmosphere.
Materials Science Forum, 2010
Several materials have been used as surgical implants since the 16th century. Materials can be im... more Several materials have been used as surgical implants since the 16th century. Materials can be implanted in the human body; however, the choice of the appropriate material is based on the required mechanical, physical, chemical, and biological properties. Until now two classes of metals namely stainless steel and cobalt-chromium-molybdenum alloys became known as materials for implant applications. They were considered suitable for surgical implant procedures but many researchers and surgeons were not completely satisfied with their performance. The main problem of the modern science is to find a material that perfectly restores tissues damaged after accidents or diseases. The trend of the current research in orthopedic prosthesis is based on the development of titanium alloys composed of non-toxic elements with low modulus of elasticity. Powder metallurgy techniques have beenused to produce controlled porous structures such as the porous coating applied for dental and orthopedic sur...
Materials Science Forum, 2010
Stainless steel (SS) powders are used in the preparation of sintered SS products. One of the appl... more Stainless steel (SS) powders are used in the preparation of sintered SS products. One of the applications of sintered SS products is as filters in the petrochemical and food processing industries. In these industries, the SS filters are subject to severe conditions associated with the removal of solid particles from the fluid. Hence, SS filters should have adequate mechanical strength and high corrosion resistance. Welding can be used to manufacture SS filters. In this study, sintered AISI 316L specimens were welded using the TIG (Tungsten Inert Gas) process. The weld joints were examined by optical microscopy and by scanning electron microscopy. Electrochemical polarization measurements were carried out to evaluate the influence of welding on the corrosion resistance of sintered filters.
Materials Science Forum, 2008
The hydrogenation decrepitation process was employed to produce sintered magnets using a mixture ... more The hydrogenation decrepitation process was employed to produce sintered magnets using a mixture of two alloys. The effect of niobium and boron content on the magnetic properties of Pr14FebalCo16BxNby-type sintered magnets was studied. Niobium and boron have a significant effect on the magnetic behavior of these permanent magnets. The optimum amount of boron was 6 at% and niobium should be kept below to 0.50 at%. The squareness factor (0.90) has been improved considerably and good overall magnetic properties (Br=1320 mT, iHc=700 kAm-1 and (BH)max=315 kJm-3) have been achieved for the sintered magnets prepared from the Pr14Fe63.85Co16B6Nb0.15 alloy.
Journal of Magnetism and Magnetic Materials, 2004
This paper reports the results of investigations carried out to determine the microstructure and ... more This paper reports the results of investigations carried out to determine the microstructure and magnetic properties of some Pr-based magnets represented by the formula Pr x Fe 77.9Àx Co 16 B 6 Nb 0.1. Bonded magnets were prepared from cast and homogenized alloys using the hydrogenation, disproportionation, desorption and recombination process. The influence of Pr content on the magnetic properties of these magnets was studied. Praseodymium content has a significant influence on the magnetic behaviour of these magnets. Examination of the microstructures of the magnets revealed that the shape of the magnetic grains (o1 mm) changed with praseodymium content.
Materials Science Forum, 2006
This paper reports the results of investigations carried out to determine the Curie temperature (... more This paper reports the results of investigations carried out to determine the Curie temperature (Tc) of some annealed praseodymium-based alloys represented by the formula Pr14Fe79.9-xCoxB6Nb0.1. The Curie temperature of these permanent magnet alloys increase linearly with the cobalt content at about (10.2±0.3) oC/at%. Pr14Fe80B6 and Pr14Fe79.9B6Nb0.1 magnetic alloys with a Tc of 290oC have been used as a standard reference. Magnets were prepared from the alloys using the hydrogenation, disproportionation, desorption and recombination (HDDR) process.
Materials Science Forum, 2010
The use of pressed and sintered aluminum, obtained by the powder metallurgy route, to produce lar... more The use of pressed and sintered aluminum, obtained by the powder metallurgy route, to produce large quantities of near-net-shaped components is increasing rapidly in the automobile industry. The production of lightweight pieces of Al by powder metallurgy has attracted increasing attention due to its unique properties. Sintering helps develop mechanical strength and other properties in commercial alloys obtained by powder metallurgy. Sintering of Al can be achieved only upon formation of a liquid phase capable of destroying the extremely stable oxide layer on the surface of the Al particles. The aim of this investigation was to analyze the effect of compaction pressure on sintering of atomized ASTM 2124 type alloy. Powder characterization was carried out using scanning electron microscopy (SEM). The specimens were axially compacted at pressures of 500, 600 and 700 MPa. Differential scanning calorimetry (DSC) was carried out to determine the sintering temperature of the alloy powder. ...
Abstract This study reports the results of investigations carried out to determine the Curie temp... more Abstract This study reports the results of investigations carried out to determine the Curie temperature (Tc) of various homogenized praseodymium-based alloys represented by the formula: Pr14Fe79. 9-xCo16B6Nbx (where x= 0, 0.01, 0.05, 0.1, 0.15, 0.50). The influence ...
Permanent magnets were produced from annealed alloys using the hydrogenation, disproportionation,... more Permanent magnets were produced from annealed alloys using the hydrogenation, disproportionation, desorption and recombination (HDDR) process. The influence of Pr concentration on the magnetic properties of these magnets was studied. Under the present processing conditions Pr has a significant influence on the magnetic behaviour of these magnetic materials. Microstructural examinations revealed that free iron was completed eliminated from all studied alloys with annealing and the grain size changed somewhat with praseodymium content. It has also been shown that to obtain bonded magnets with optimum magnetic properties the praseodymium content in these alloys should be around 13.5 at%.
Materials Research, Jun 1, 2005
In this investigation, the corrosion resistance of AISI 316 SS filters prepared with powders in t... more In this investigation, the corrosion resistance of AISI 316 SS filters prepared with powders in the size ranges 74-44 µm and 210-105 m and compacted with pressures of 300 MPa and 400 MPa has been evaluated in naturally aerated 0.5 M H 2 SO 4 solution at 25 °C. Weight loss of filters manufactured with compacting pressure of 400 MPa were significantly higher than that of filters compacted at 300 MPa. The filter compacted at 400 MPa had higher carbon and nitrogen contents compared to those compacted at 300 MPa. The former also had chromium rich precipitates and oxides in the grain boundaries. The pores in filters compacted at 400 MPa were smaller than in filters compacted at 300 MPa. Smaller pores favor the formation of concentration cells and consequently, increased crevice corrosion.
In this present work Ti-13Nb-13Zr alloy was produced by PM using planetary ball mill with zirconi... more In this present work Ti-13Nb-13Zr alloy was produced by PM using planetary ball mill with zirconium oxide grinding bowl and balls to reduce contamination. The effect of milling time upon microstructure and microhardness was studied. Powders have been produced by hydrogenation of Ti, Nb and Zr at 1MPa. Milling speed was 200 rpm during 90 to 360 min. Sintering was carried out at 1150°C during 10h. Powder size distribution was analyzed using CILAS equipment and chemically characterized by X-Ray Fluorescence (XRF). Microhardness was determined by means of a Vickers microhardness tester. Microstructure and phases were analyzed employing scanning electron microscopy (SEM) and X-Ray diffraction.
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Papers by Luzinete Barbosa