The Equal Channel Angular Extrusion in Grade 2 and 4 commercially pure titanium raises the yield strength, ultimate tensile strength, elongation, fatigue limit, besides to attend the requirements of torque and angle of rupture for implants.
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A metastable beta TMZF alloy was tested by isothermal compression under different conditions of deformation temperature (923 to 1173 K), strain rate (0.172, 1.72, and 17.2 s−1), and a constant strain of 0.8. Stress–strain curves,... more
A metastable beta TMZF alloy was tested by isothermal compression under different conditions of deformation temperature (923 to 1173 K), strain rate (0.172, 1.72, and 17.2 s−1), and a constant strain of 0.8. Stress–strain curves, constitutive constants calculations, and microstructural analysis were performed to understand the alloy’s hot working behavior in regards to the softening and hardening mechanisms operating during deformation. The primary softening mechanism was dynamic recovery, promoting dynamic recrystallization delay during deformation at higher temperatures and low strain rates. Mechanical twinning was an essential deformation mechanism of this alloy, being observed on a nanometric scale. Spinodal decomposition evidence was found to occur during hot deformation. Different models of phenomenological constitutive equations were tested to verify the effectiveness of flow stress prediction. The stress exponent n, derived from the strain-compensated Arrhenius-type constitu...
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Resumo: O presente trabalho teve como objetivo a determinação dos parâmetros ótimos do processo de manufatura aditiva de Fusão Seletiva a Laser (FSL) para o aço 316L visando a obtenção de peças com alta densidade, utilizando equipamento... more
Resumo: O presente trabalho teve como objetivo a determinação dos parâmetros ótimos do processo de manufatura aditiva de Fusão Seletiva a Laser (FSL) para o aço 316L visando a obtenção de peças com alta densidade, utilizando equipamento fabricado no Brasil. Foi realizada também uma completa caracterização estrutural tanto da matéria prima utilizada (pó comercial) quanto das peças mais densas obtidas. As propriedades mecânicas das peças produzidas por FSL também foram avaliadas e comparadas com peça fabricada de forma convencional. Foi observado que a densidade das peças aumenta com o aumento da densidade volumétrica de energia fornecida pelo laser até atingir um patamar de máxima densidade. Um modelo polinomial foi proposto correlacionando a densidade volumétrica de energia utilizada com a densidade final da peça. As peças produzidas por FSL mostraram uma elevada densificação (densidade relativa superior a 99,49%) com uma reduzida porosidade homogeneamente dispersa no material. Uma ...
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Research Interests: Materials Engineering, Materials Science, Nanoindentation, Scanning Electron Microscopy, Metallic Glass, and 14 moreCasting, Differential scanning calorimetry, Copper, Non crystalline solids, Composite Material, Alloy, Mechanical Testing, Finite element simulation, X ray diffraction, Thermal Stability, Free volume, Elastic Modulus, Thermal Properties, and Experimental Data
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The corrosion resistance of Fe–M–B–Cu alloys in which M is a transition metal of two first series, particularly concerning the effect of composition and also concerning the affect of corrosion on magnetic properties have not been... more
The corrosion resistance of Fe–M–B–Cu alloys in which M is a transition metal of two first series, particularly concerning the effect of composition and also concerning the affect of corrosion on magnetic properties have not been evaluated. In this paper, the effect of composition and partial crystallization on corrosion resistance of Fe80Nb3.5Zr3.5B12Cu1, Fe80Nb3.5Mo3.5B12Cu1, Fe80Zr3.5Mo3.5B12Cu1 and Fe80Mo7B12Cu1 amorphous alloys and its
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Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Powder Metallurgy, Microstructure, and 14 moreMetallurgy, Nanomaterials, Nanostructured materials, Aluminum, Ingenieria y ciencias de los Materiales, Aluminium Alloys, Gas Atomized Powder, Aluminum Alloys, Quasicrystals, Aluminium, Extrusion, Quasicrystal, Rapid solidification, and Melt Spinning
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Abstract Highly ordered arrays of TiO 2 nanotubes are being considered as very promising to improve the osseointegration of titanium based implants to living tissues. However, this improvement must be accompanied by no drawback in the... more
Abstract Highly ordered arrays of TiO 2 nanotubes are being considered as very promising to improve the osseointegration of titanium based implants to living tissues. However, this improvement must be accompanied by no drawback in the mechanical properties, which is the case of several surface modification techniques available for biomaterials. Therefore, this work investigated for the first time the effect of the surface modification by TiO 2 nanotubes formation on the fatigue response of Ti-6Al-4V biomedical alloy. Highly organized nanotubes with an average diameter and length respectively of 90 and 600 nm were successfully produced by electrochemical anodization. Based on the standardized staircase method, fatigue tests of the treated specimens were conducted in physiological media at 37 °C, and compared to the untreated polished specimens. The mean and standard deviation values of the fatigue limit calculated through the Dixon-Mood equations were equal for both surface conditions. This result suggests that the employed condition of anodization was satisfactory on growing a nanotubes coating that was not deleterious to the fatigue performance of the alloy, what is a relevant achievement that assures the possibility of having high osseointegration and at the same time keeping the mechanical properties.
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Shape memory alloys (SMAs) are a class of material that undergoes a reversible shape change after a plastic deformation. The recovery of the original shape is possible due to a structural transformation upon heating to a critical... more
Shape memory alloys (SMAs) are a class of material that undergoes a reversible shape change after a plastic deformation. The recovery of the original shape is possible due to a structural transformation upon heating to a critical temperature. The shape memory effect is related to a martensitic-austenitic transformation from a phase with a low symmetry (martensite) to a high-temperature phase (parent phase) [1]. Cu-based shape memory alloys have the advantage of large thermal and electrical conductivities and the system Cu-Al-Ni alloys are quite attractive due to better stabilisation against aging phenomena [2].
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Nickel-based alloys with polycrystalline structure are known for their high corrosion resistance and good mechanical strength. Moreover, the possibility of amorphization of nickel-based alloys could improve both properties. In this work,... more
Nickel-based alloys with polycrystalline structure are known for their high corrosion resistance and good mechanical strength. Moreover, the possibility of amorphization of nickel-based alloys could improve both properties. In this work, the new Ni61.0Nb35.5B3.0Si0.5 alloy was processed by melt-spinning and conformation spray to produce amorphous materials. Subsequently, the as-cast samples were heat-treated to result in partial crystalline fractions. The structures were characterized by x-ray diffraction (DRX), differential scanning calorimetry (DSC), light optical (LOM) and scanning electron microscopy (SEM). The polarization curves of all structural conditions obtained in 3.5% NaCl aqueous solution at 25 C indicated the positive effect of amorphous phase in corrosion tests. Indeed, all studied conditions produced a large passivation potential range, even with partial crystalline presence. Furthermore, the measured passivation current density was proportional to crystalline conten...
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Abstract This work studied the corrosion behaviour of Ti-12Mo-6Zr-2Fe alloy with different surface conditions: untreated and chemically treated (CST), anodised nanotubes (Nt) and nanopores (NP). These samples were immersed in simulated... more
Abstract This work studied the corrosion behaviour of Ti-12Mo-6Zr-2Fe alloy with different surface conditions: untreated and chemically treated (CST), anodised nanotubes (Nt) and nanopores (NP). These samples were immersed in simulated body fluid (SBF) for 1, 7, and 14 days. Samples with Nt and NP displayed higher corrosion resistance and lower passivation current (ipass) than untreated and CST samples after 14 days resting in SBF. Furthermore, traditional equivalent circuits and a new two-channel transmission line model were employed to efficiently simulate the electrochemical impedance spectroscopy (EIS) data of the different surface conditions.
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Abstract In this paper, the Gum Metal Ti–29Nb–13Ta-4.6Zr-xO with two different oxygen contents (2200 and 4600 ppm) was prepared by high-pressure torsion (HPT) and their microstructural evolution, thermal stability, physical and mechanical... more
Abstract In this paper, the Gum Metal Ti–29Nb–13Ta-4.6Zr-xO with two different oxygen contents (2200 and 4600 ppm) was prepared by high-pressure torsion (HPT) and their microstructural evolution, thermal stability, physical and mechanical properties were investigated for specimens prepared under different processing conditions. An increase in the β-phase stability at the expense of αʺ, as well as in the hardness was observed with the combined effect of oxygen addition and HPT processing. The increase in hardness was attributed to the microstructural refinement, to the creation of a high density of defects, and to the stress-induced ω-phase formation, which were all obtained due to the severe plastic deformation. Besides that, oxygen solid solution hardening provides a great increase in hardness. Vickers microhardness of approximately 400 HV was obtained for samples with higher oxygen content and deformed by HPT. The elastic modulus did not change significantly for the different oxygen levels, with values of 53–66 GPa. The typical Gum Metal properties were attained in the present paper, and they are directly related to its deformation mechanisms such as slip, stress-induced αʺ-martensite as well as reverse martensitic transformation (αʺ → β). The unique Gum Metal properties combined with the obtained increase in hardness make these two alloys very well suited for biomedical applications such as implants.
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Abstract This paper provides insights into microstructure control of recycled Al-7Si-3Cu alloy, which is widely used in the automotive industry. Here we report a detailed study of the Mn and V addition effects on the morphological... more
Abstract This paper provides insights into microstructure control of recycled Al-7Si-3Cu alloy, which is widely used in the automotive industry. Here we report a detailed study of the Mn and V addition effects on the morphological modification of the quasicrystal approximant α-phase. We demonstrate that the addition of 0.3 wt% of V and 1.0 wt% of Mn to the Al-7Si-3Cu-1Fe alloy combined with the solidification features of spray-forming leads to the formation of a microstructure containing nano-submicron size quasicrystal approximant α-phase. Such microstructure results in an improved combination of strength and ductility up to 250 °C. Rotary swaging and Si globulization treatment performed as secondary processing leads to further improvement of the alloy’s tensile properties at different temperatures. The present work provides significant contributions on recycling of alloys without addition of primary Al and a prospect for more valuable applications.
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The lightweight Fe–Mn–Al–C steels have drawn considerable attention from the literature due to their outstanding combination of high ductility and specific strength. Although the mechanical behavior of such steels has been extensively... more
The lightweight Fe–Mn–Al–C steels have drawn considerable attention from the literature due to their outstanding combination of high ductility and specific strength. Although the mechanical behavior of such steels has been extensively studied, the effect of Al when no C and Si are added has not been investigated in detail. For this reason, the main objective of this work was to study the microstructural evolution and mechanical behavior of carbon and silicon-free high-Mn steels with different aluminum contents. Alloys with 0, 2.5, and 5 wt. % Al were processed by spray forming to ensure high homogeneity and a fully austenitic microstructure. Cold rolling and annealing were performed to obtain a fine grain-sized material. The mechanical properties were similar regardless of the Al content, especially the work hardening rate. Deformation twinning and strain-induced phase transformation were not observed for any of the compositions. Additionally, a dislocation cell-like structure was o...
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Abstract Cu-based shape memory alloys (SMAs) show better thermal and electrical conductivity, lower cost and are easier to process than traditional Ti-based SMAs, but they exhibit a lower ductility and lower fatigue life. These properties... more
Abstract Cu-based shape memory alloys (SMAs) show better thermal and electrical conductivity, lower cost and are easier to process than traditional Ti-based SMAs, but they exhibit a lower ductility and lower fatigue life. These properties can be improved by decreasing the grain size and reducing microstructural segregations, which may be obtained using laser surface remelting treatments. The aim of the present work was to produce and characterize laser remelted Cu-11.85Al-3.2Ni-3Mn SMA plates. Twelve plates with the dimensions of 50×10×1.5 mm were produced by suction casting in a first step. The surface of the plates was remelted afterwards with a laser beam power of 300 W, hatching of 50% and using three different scanning speeds: 100, 300 and 500 mm/s. The plates were characterized by optical and scanning electron microscopy, X-ray diffraction, differential scanning calorimetry as well as by tensile and microhardness tests. The remelted region showed a T morphology, with average thickness of 52, 29 and 23 µm for the plates remelted with scanning speeds of 100, 300 and 500 mm/s, respectively. In the plates remelted with 100 and 300 mm/s, some pores were found around the center of the track, due to the keyhole instability. The same phase formed in the as-cast sample was obtained in the laser remelted coatings: the monoclinic β′1 martensitic phase with zig-zag morphology. However, the laser treated samples exhibit lower transformation temperatures than the as-cast sample, due to grain refinement at the surface. They also show an improvement in the mechanical properties, with an increase of up to 162 MPa in fracture stress, up to 2.2% in ductility and up to 20.9 HV in microhardness when compared with the as-cast sample, which makes the laser surface remelting a promising method for improving the mechanical properties of Cu-based SMAs.
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Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Laser, Materials, and 12 moreDifferential scanning calorimetry, Coating, Composite Material, Sputtering, Crystallinity, Shape Memory Alloy, Alloy, Surface and Coatings Technology, Thermal Stability, DDC, Selective Laser Melting, and Sputter Deposition
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Silicon-iron alloys with silicon content about 6.5wt.%Si offer a great potential for applications aiming reduction of core loss in electric parts. Deposits of the Fe-6.5wt%Si alloy produced by spray forming were annealed at temperatures... more
Silicon-iron alloys with silicon content about 6.5wt.%Si offer a great potential for applications aiming reduction of core loss in electric parts. Deposits of the Fe-6.5wt%Si alloy produced by spray forming were annealed at temperatures between 400 and 1300oC, during 1h in vacuum. The grain size has a great importance to the magnetic properties. In the present work, it was analyzed the influence of the metallography parameters in order to get the best accuracy to determine the grain size according to ASTM 112-96. Chemical composition, time and temperature of specific etchings were modified and tested in different conditions of observation in light microscopy. Bright field, polarized light and dark field were used in the samples aiming to measure the grain size. The best etchings were Nital 10% and Marshall, both at room temperature. The results of grain measurement are presented in their relationship with the magnetic properties.
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ABSTRACT Cu-based shape memory alloys (SMA) in the range of Cu-(11.8-13.5)Al-(3.2-4)Ni-(2-3)Mn (wt%) exhibit high thermal and electrical conductivity, combine good mechanical properties with a pronounced shape memory effect, and are low... more
ABSTRACT Cu-based shape memory alloys (SMA) in the range of Cu-(11.8-13.5)Al-(3.2-4)Ni-(2-3)Mn (wt%) exhibit high thermal and electrical conductivity, combine good mechanical properties with a pronounced shape memory effect, and are low cost (Dutkiewicz et al., 1999). Their processing requires high cooling rates to reduce grain size, prevent decomposition of the ß phase into equilibrium phases, and induce martensite transformation. In this investigation, Cu-11.85Al-3.2Ni-3Mn (wt%) shape memory alloy was processed by spray forming, a rapid solidification technique that involves cooling rates of 101 to 104 K/s, to determine the potential of producing deposits with adequate microstructure, homogeneity and porosity for the manufacture of SMA near net shape parts. To this end, 5.2 kg of alloy with nominal composition was atomized with nitrogen gas under a pressure of 0.5 MPa and a gas-metal ratio (GMR) of 1.93. The atomized material was deposited at 60 rpm on a rotating steel substrate positioned 350 mm below the gas nozzle. The microstructure of the deposit was characterized by optical and scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. The deposit with an effective diameter of 240 mm and 75 mm height presented equiaxial grains with a martensite microstructure. Grain sizes varied from 25 μm in the lower region (contact with the steel substrate) to 160 μm in the upper region of the deposit. Measurements of the reverse martensite transformation temperature of the deposit in different regions revealed its strong influence on the grain size.
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Abstract Surface engineering is an effective method to extend the lifespan of carbon steels submitted to severe wear degradation. In this work, the surface of a low carbon steel (AISI 1020) was protected by a boron-modified stainless... more
Abstract Surface engineering is an effective method to extend the lifespan of carbon steels submitted to severe wear degradation. In this work, the surface of a low carbon steel (AISI 1020) was protected by a boron-modified stainless steel coating produced by selective laser melting (SLM). Commercial precursors such as 2205 duplex stainless steel and ferrous-alloy (Fe-B) were used to produce boron-modified steel powders by two different routes: i) gas atomization, and ii) gas atomization followed by mechanical milling of large particles (to reduce the particles’ size and to add a solid lubricant – hexagonal boron nitride, h-BN). Thick coatings (200 – 600 μm) metallurgically bonded to the substrate were produced with reduced dilution, characterized by refined, hard and rigid borides homogeneously distributed within the predominant ferritic matrix. The boron-modified steel coatings were hard (~800 HV0.5) and wear-resistant, since the specific wear rate was ~4.5 × 10−5 mm3·N−1·m−1, much inferior to that of the soft (~120 HV0.5) AISI 1020 substrate (~1.8 × 10−3 mm3·N−1·m−1). Although recognized as solid-lubrificant, the coating produced by powder containing h-BN additions did not exhibit reduced coefficient of friction. Given the high temperatures achieved during SLM process, the h-BN may decompose, being the remaining content insufficient to enable the formation of an effective lubrificating layer. The present work contributes to widespread the use of SLM to produce wear-resistant protective coatings using boride-reinforced stainless steels.
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Abstract In this work, theoretical composition design and thermo-mechanical treatments were combined in order to improve the mechanical compatibility of a metastable β-type Ti–29Nb–13Ta–4Mo (wt%) alloy. Also, the influence of Mo and O... more
Abstract In this work, theoretical composition design and thermo-mechanical treatments were combined in order to improve the mechanical compatibility of a metastable β-type Ti–29Nb–13Ta–4Mo (wt%) alloy. Also, the influence of Mo and O alloying elements were investigated. By applying cold rolling and low temperature aging (673K during 20 and 100 min) different behaviours in microstructure and mechanical properties were identified. Alloys with Ultimate Tensile strength-UTS = 854 MPa and Elastic Modulus = 65 GPa were successfully fabricated. The microstructure responsible for that behaviour consisted mainly of β-matrix and ω-precipitation obtained via cold rolling plus short-time aging at low temperature, i.e. 673K for 20 min. These precipitates increase the strength of the material by hindering the motion of dislocations while the β-matrix with relatively high content of β-stabilizers (such, Mo) gives rise to the observed low elastic modulus. By extending aging time (100 min), a higher UTS is reached, but a slight increase in Elastic Modulus is also observed. The addition of oxygen increased mechanical and physical properties by favouring ω-phase formation. Whereas, Mo content increased β-stability, and in solution treated condition, only β-phase could be observed.