In most casting applications, dendritic microstructure morphology is not desired because it leads to poor mechanical properties. Forced convection causing sufficient shearing in the mushy zone of the partially solidified melt is one of the means to suppress this dendritic growth. The dendrites formed at the solid-liquid interface are detached and carried away due to strong fluid flow to form slurry. This slurry, consisting of rosette or globular particles, provides less resistance to flow even at a high solid fraction and can easily fill the die-cavity. The stated principle is the basis of a new manufacturing technology called “semi-solid forming” (SSF), in which metal alloys are cast in the semi-solid state. This technique has numerous advantages over other existing commercial casting processes, such as reduction of macrosegregation, reduction of porosity and low forming efforts. Among all currently available methods available for large scale production of semisolid slurry, the cooling slope is considered to be a simple but effective method because of its simple design and easy control of process parameters, low equipment and running costs, high production efficiency and reduced inhomogeneity. With this perspective, the primary objective of the present research is to investigate, both experimentally and numerically, convective heat transfer and solidification on a cooling slope, in addition to the study of final microstructure of the cast billets. Some key process parameters are identified, namely pouring temperature, slope angle, slope length, and slope cooling rate. A systematic scaling analysis is performed in order to understand the relative importance of the parameters in influencing the final properties of the slurry and microstructure after solidification. A major part of the present work deals with the development of an experimental set up with careful consideration of the range of process parameters involved by treating the cooling slope as a heat exchanger. Subsequently, a comprehensive numerical model is developed to predict the flow, heat transfer, species concentration solid fraction distribution of aluminum alloy melt while flowing down the cooling slope. The model uses a variable viscosity relation for slurry. The metal-air interface at the top during the melt flow is tracked using a volume of fluid (VOF) method. Solidification is modeled using an enthalpy based approach and a volume averaged technique. The mushy region is modeled as a multi-layered porous medium consisting of fixed columnar dendrites and mobile equiaxed or fragmented grains. In addition, the solidification model also incorporates a fragmentation criterion and solid phase movement. The effects of key process parameters on flow behavior involving velocity distribution, temperature distribution, solid fractions at the slope exit, and macrosegregation, are studied numerically and experimentally for aluminium alloy A356. The resulting microstructures of the cast billets obtained from the experiments are studied and characterized. Finally the experimental results are linked to the model predictions for establishing the relations involving interdependence of the stated key process parameters in determining the quality of the final cast products. This study is aimed towards providing the necessary guidelines for designing a cooling slope and optimizing the process parameters for desirable quality of the solidified product.

Call number: LD2668 .T4 1985 J365 / Master of Science

Mg alloys have spurred a renewed academic and industrial interest because of their ultra-light-weight and high specific strength properties. Hexagonal close packed Mg has low deformability and a high plastic anisotropy between basal and non-basal slip systems at room temperature. Alloying with Li and other elements is believed to counter this deficiency by activating non-basal slip by reducing their nucleation stress. In this work I study how Li addition affects deformation mechanisms in Mg using atomistic simulations. In the first part, I create a reliable and transferable concentration dependent embedded atom method (CD-EAM) potential for my molecular dynamics study of deformation. This potential describes the Mg-Li phase diagram, which accurately describes the phase stability as a function of Li concentration and temperature. Also, it reproduces the heat of mixing, lattice parameters, and bulk moduli of the alloy as a function of Li concentration. Most importantly, our CD-EAM potential reproduces the variation of stacking fault energy for basal, prismatic, and pyramidal slip systems that influences the deformation mechanisms as a function of Li concentration. This success of CD-EAM Mg-Li potential in reproducing different properties, as compared to literature data, shows its reliability and transferability. Next, I use this newly created potential to study the effect of Li addition on deformation mechanisms in Mg-Li nanocrystalline (NC) alloys. Mg-Li NC alloys show basal slip, pyramidal type-I slip, tension twinning, and two-compression twinning deformation modes. Li addition reduces the plastic anisotropy between basal and non-basal slip systems by modifying the energetics of Mg-Li alloys. This causes the solid solution softening. The inverse relationship between strength and ductility therefore suggests a concomitant increase in alloy ductility. A comparison of the NC results with single crystal deformation results helps to understand the qualitative and quantitative effect of Li addition in Mg on nucleation stress and fault energies of each deformation mode. The nucleation stress and fault energies of basal dislocations and compression twins in single crystal Mg-Li alloy increase while those for pyramidal dislocations and tension twinning decrease. This variation in respective values explains the reduction in plastic anisotropy and increase in ductility for Mg-Li alloys.

Estudou-se o comportamento de desgaste sob deslizamento em múltiplos passes de pinos fixos de liga metálica friccionados contra discos rotativos de laminados compósitos de matriz polimérica fortalecidos com fibras contínuas de carbono (C), para distintas cargas aplicadas e temperaturas de ensaio. Determinou-se a perda de volume por desgaste dos diversos pares tribológicos, e avaliaram-se os principais aspectos das superfícies e dos produtos gerados durante o processo de desgaste. Concluiu-se que o par formado pelo aço inoxidável martensítico PH 15-5 e o laminado compósito termoplástico C-PPS (poli-sulfeto de fenileno) apresentou o menor desgaste na maioria das circunstâncias avaliadas. A liga Ti6Al4V foi a pior opção dentre os pinos metálicos, independentemente do laminado compósito empregado, devido à baixa resistência ao cisalhamento e alta rugosidade superficial do metal, a qual prejudicou o ancoramento de filmes poliméricos de transferência. O ótimo desempenho do aço PH resultou de sua alta dureza e da adequada rugosidade superficial para o efetivo ancoramento do filme de transferência. O laminado compósito C-PPS se mostrou mais susceptível às variações na carga de contato, enquanto que o C-EPX (Epóxi) foi mais sensível à temperatura de ensaio. Filmes poliméricos de transferência atuaram como lubrificante do sistema tribológico, preservando ambos o pino metálico e o disco compósito de um desgaste excessivo. A natureza dos produtos de desgaste, sua geometria, seu tamanho médio e sua distribuição de tamanhos dependeram fortemente do disco rotativo de laminado compósito e das condições de ensaio de desgaste, e afetaram sobremaneira, como terceiro corpo abrasivo, o subseqüente processo de desgaste dos pares de fricção metal-compósito. Os resultados obtidos são potencialmente úteis na especificação de juntas mecânicas aeronáuticas mais apropriadas de laminados compósitos de matriz polimérica unidos por intermédio de prendedores metálicos. / Multipass sliding wear behavior of static metal alloy pins rubbing against rotating carbon fiber reinforcing polymer matrix composite laminate disks has been studied for different applied loads and test temperatures. The volume loss due wear has been determined for several tribological metal / composite systems, and the main aspects of wear surfaces and debris have been evaluated. It has been concluded that the best performance was achieved in very most cases by the PH15-5 steel pin contacting the C-PPS (poly-phenylene sulphide) disk. The Ti6Al4V alloy displayed the worst performance among the metal pins, regardless the employed composite laminate, as a result of the metal´s low shear strength and high surface roughness, which impaired the formation of polymer transfer films. The outstanding performance of PH steel pins derived from its high hardness and proper surface roughness that favored the transfer film formation. The C-PPS composite laminate was more sensitive to contact load variations, whereas the C-EPX laminate was more susceptible to the test temperature. Polymer transfer films acted as lubricant in the tribological system, preserving both the metallic pin and the composite disk from wearing in excess. The nature of wear debris, their geometry, mean size, and size distribution strongly depended on the composite laminate disk as well as on testing conditions, and affected overwhelmingly, as third body abrasive particles, the subsequent wear process of metal / composite friction pairs. The obtained results are potentially useful for the specification of more equalized aircraft mechanical joints comprising polymer matrix composite laminates and metallic fasteners.

Foi efetuada a caracterização microestrutural de 10 ligas dos sistemas urânio-nióbio (U-10Nb; U-15Nb; U-20Nb), urânio-zircônio (U- 10Zr; U-15Zr, U-20Zr) e urânio-nióbio-zircônio (U-2,5Nb-2,5Zr; U-5Nb- 5Zr; U-7,5Nb-7,5Zr; U-10Nb-10Zr), no canto rico em urânio. As ligas estudadas são candidatas ao uso como elementos combustíveis tipo placa, utilizados tanto em reatores nucleares de pesquisa como em reatores nucleares de potência. As ligas foram preparadas por fusão a plasma em forno com eletrodo não consumível de tungstênio. Após várias fusões, as amostras sofreram tratamento térmico de homogeneização a 1000ºC por 96 horas, com resfriamento em água. Em seguida, as amostras homogeneizadas foram recozidas a 700 e a 500ºC, com resfriamento em água. No total, foram estudadas 40 amostras de 10 ligas diferentes em 4 condições diferentes: bruto de fundição, homogeneizadas a 1000ºC e envelhecidas a 700 e a 500ºC. Foram utilizadas várias técnicas complementares de caracterização microestrutural: microscopia óptica, microscopia eletrônica de varredura com auxilio de microanálise por dispersão de energia de raios X, difração de raios X com auxílio do método de análise de Rietveld, e medidas de microdureza Vickers. Os resultados mostraram que os elementos de liga Nb e Zr estabilizam a fase alotrópica &#947 do urânio e atrasam a transformação de γ para β. Neste aspecto, o Nb é mais eficaz que o Zr. Além disto, podem ocorrer durante o resfriamento transformações martensíticas γ→α\', β→α′ e possivelmente γ→γ°. A temperatura de início de transformação martensítica (Ms) formadora da fase diminui com a adição dos elementos de liga estudados. Ms intercepta a temperatura ambiente entre as composições U-5Nb-5Zr e U-7,5Nb-7,5Zr. Foi verificado também que a reação peritetóide α + γ2→ δ do sistema U-Zr possui uma cinética lenta e não pode ser detectada nos tempos e temperaturas estudados. Em algumas ligas foi possível reter na temperatura ambiente ligas com microestrutura martensítica dúcteis, que permitem a conformação mecânica a frio, o que é de significativo interesse tecnológico. / The microstructures of 10 uranium-rich alloys of the uraniumniobium (U-10Nb; U-15Nb; U-20Nb), uranium-zirconium (U-10Zr; U- 15Zr;U-20Zr) and uranium-niobium-zirconium (U-2.5Nb-2.5Zr; U-5Nb-5Zr; U-7.5Nb-7.5Zr; U-10Nb-10Zr)systems have been characterized. The studied alloys are considered for plate-type nuclear fuels fabrication used both in nuclear research reactors and in nuclear power reactors. The alloys were melted by arc plasma methods employing nonconsumable tungsten cathode. After several fusions, samples were subjected to homogenizing heat treatment at 1000ºC for 96 hours and then quenched in water. Then the samples were annealed at 700 and 500ºC. The microstructural characterization encompassed 40 samples of 10 different alloys composition in four different conditions: as cast, homogenized at 1000°C and aged at 700 and 500ºC. Microstructural characterization was performed using several complementary techniques: optical microscopy; scanning electron microscopy with energy-dispersive X-ray analysis; X-ray diffraction with the aid of the Rietveld analysis method; and Vickers microhardness measurements. The results showed that the Nb and Zr additions have stabilized the uranium γ-phase and delayed the γ and β phase transformation. In this regard, Nb was more effective than Zr. However, during cooling martensitic transformations γ→α\', β→α\' and possibly γ→γ° may occur. The martensitic transformation start temperature (Ms), which produces the phase , decreased with Nb and Zr additions. Ms intersected room temperature between the compositions U-5Nb-5Zr e U- 7,5Nb-7,5Zr. It was found that the peritectoid reaction α + γ2 → δ of the U-Zr system showed a very slow kinetics and could not be detected in the range of the studied times and temperatures. An important result of the technological point of view is that in some alloys it was possible to retain at room temperature a ductile martensitic microstructure, allowing cold forming.

Foi efetuada a caracterização microestrutural de 10 ligas dos sistemas urânio-nióbio (U-10Nb; U-15Nb; U-20Nb), urânio-zircônio (U- 10Zr; U-15Zr, U-20Zr) e urânio-nióbio-zircônio (U-2,5Nb-2,5Zr; U-5Nb- 5Zr; U-7,5Nb-7,5Zr; U-10Nb-10Zr), no canto rico em urânio. As ligas estudadas são candidatas ao uso como elementos combustíveis tipo placa, utilizados tanto em reatores nucleares de pesquisa como em reatores nucleares de potência. As ligas foram preparadas por fusão a plasma em forno com eletrodo não consumível de tungstênio. Após várias fusões, as amostras sofreram tratamento térmico de homogeneização a 1000ºC por 96 horas, com resfriamento em água. Em seguida, as amostras homogeneizadas foram recozidas a 700 e a 500ºC, com resfriamento em água. No total, foram estudadas 40 amostras de 10 ligas diferentes em 4 condições diferentes: bruto de fundição, homogeneizadas a 1000ºC e envelhecidas a 700 e a 500ºC. Foram utilizadas várias técnicas complementares de caracterização microestrutural: microscopia óptica, microscopia eletrônica de varredura com auxilio de microanálise por dispersão de energia de raios X, difração de raios X com auxílio do método de análise de Rietveld, e medidas de microdureza Vickers. Os resultados mostraram que os elementos de liga Nb e Zr estabilizam a fase alotrópica &#947 do urânio e atrasam a transformação de γ para β. Neste aspecto, o Nb é mais eficaz que o Zr. Além disto, podem ocorrer durante o resfriamento transformações martensíticas γ→α\', β→α′ e possivelmente γ→γ°. A temperatura de início de transformação martensítica (Ms) formadora da fase diminui com a adição dos elementos de liga estudados. Ms intercepta a temperatura ambiente entre as composições U-5Nb-5Zr e U-7,5Nb-7,5Zr. Foi verificado também que a reação peritetóide α + γ2→ δ do sistema U-Zr possui uma cinética lenta e não pode ser detectada nos tempos e temperaturas estudados. Em algumas ligas foi possível reter na temperatura ambiente ligas com microestrutura martensítica dúcteis, que permitem a conformação mecânica a frio, o que é de significativo interesse tecnológico. / The microstructures of 10 uranium-rich alloys of the uraniumniobium (U-10Nb; U-15Nb; U-20Nb), uranium-zirconium (U-10Zr; U- 15Zr;U-20Zr) and uranium-niobium-zirconium (U-2.5Nb-2.5Zr; U-5Nb-5Zr; U-7.5Nb-7.5Zr; U-10Nb-10Zr)systems have been characterized. The studied alloys are considered for plate-type nuclear fuels fabrication used both in nuclear research reactors and in nuclear power reactors. The alloys were melted by arc plasma methods employing nonconsumable tungsten cathode. After several fusions, samples were subjected to homogenizing heat treatment at 1000ºC for 96 hours and then quenched in water. Then the samples were annealed at 700 and 500ºC. The microstructural characterization encompassed 40 samples of 10 different alloys composition in four different conditions: as cast, homogenized at 1000°C and aged at 700 and 500ºC. Microstructural characterization was performed using several complementary techniques: optical microscopy; scanning electron microscopy with energy-dispersive X-ray analysis; X-ray diffraction with the aid of the Rietveld analysis method; and Vickers microhardness measurements. The results showed that the Nb and Zr additions have stabilized the uranium γ-phase and delayed the γ and β phase transformation. In this regard, Nb was more effective than Zr. However, during cooling martensitic transformations γ→α\', β→α\' and possibly γ→γ° may occur. The martensitic transformation start temperature (Ms), which produces the phase , decreased with Nb and Zr additions. Ms intersected room temperature between the compositions U-5Nb-5Zr e U- 7,5Nb-7,5Zr. It was found that the peritectoid reaction α + γ2 → δ of the U-Zr system showed a very slow kinetics and could not be detected in the range of the studied times and temperatures. An important result of the technological point of view is that in some alloys it was possible to retain at room temperature a ductile martensitic microstructure, allowing cold forming.

Development of the faster and denser magnetic memory storage elements has been an active area of research since early 20th century. The path of research on magnetization manipulation began with firstly changing the magnetization state of a medium in an external magnetic field, then heating of a medium and magnetizing with a permanent magnet was explored, while the latest efforts have been focused on switching the magnetization only by a polarized laser light. Nowadays due to the technological advancement of lasers and material fabrication methods, the search and development process of magnetic memory elements is much faster. The implementation of such technologies, however, relies on finding suitable magnetic materials which would allow for a fast magnetization writing and read-out processes and would remain magnetized, even with the reduced dimensions. Ferrimagnetic rare Earth - transition metal (RE-TM) alloys have been used for fabricating magneto-optical recording media already since the 1990’s. Relatively recently, in 2007, it was demonstrated that the ferrimagnetic GdFeCo alloy magnetization state can be switched using only circularly polarized laser light. Hence, ferrimagnetic RE-TMalloys could be suitable candidates for all-optical light-induced magnetization switching (AOS), without any external magnetic field. Another combination of RE-TM alloys that was shown to exhibit AOS is ferrimagnetic amorphous alloys containing terbium and cobalt (Tb:Co). They have attracted attention due to their strong out-of-plane magnetic anisotropy, high magneto-optical activity and amorphicity, which makes them attractive from a fabrication point of view since a variety of substrates and buffer layers could be used for growing such layers. In this Thesis, TbCo alloys are investigated in order to examine how the magnetic, optical and magneto-optical properties could be tuned by varying the elemental ratio and film thickness. The main question that was addressed here was whether such a system is suitable for fabrication of nanosized magnetic elements as the building blocks for the magnetic memory applications. TbCo alloys were prepared as thin films by magnetron co-sputtering method onto different substrates and buffer layers. Films were characterized using a variety of techniques such as an ion beam analysis, an x-ray reflectivity and diffraction, and magneto-optical characterization techniques. It was observed that the properties of such alloys depend not only on the Tb:Co ratio but also on the film thickness and an underlying buffer layer. Magnetization compensation point, at which the magnetization of a film is zero, as in an antiferromagnet, can be modified depending on the buffer layer. All-optical switching (AOS) of magnetization experiments were performed on the fabricated samples. It was determined that AOS with at least 50-100 laserpulses can be achieved for the films grown directly onto fused silica substrates and with the compositions above the magnetization compensation point at room temperature, in the range of 24 - 30 at.% Tb. In the Outlook, the initial efforts of patterning the films into the arrays of nanosized elements are presented. It is demonstrated that after the lithographic patterning of the films, the resulting nanosized elements remained out-of-plane magnetized. In this work it is shown that the ferrimagnetic TbCo alloy system is a potential candidate material for bothfacilitating AOS and the fabrication of arrays of nanomagnets. Combining the TbCo alloys,which show AOS, together with a suitable buffer layer and patterning the hybrid structure,could enable selective element-by-element magnetization switching for the magnetic memorystorage devices.

<p>The present thesis concerns applications of first principles electronic structure calculations in conjunction with methods of statistical mechanics for simulations of transition metal alloys both in the bulk and at surfaces.</p><p>A fully relativistic generalization of the exact muffin-tin orbitals (EMTO) method has been developed. The method accurately takes into account spin-orbit coupling and allows one to calculate orbital polarization and magneto-crystalline anisotropy in magnetic systems as well as increasing the range of applicability of the EMTO method to heavy elements. A new direct-exchange Monte Carlo (DEMC) method has been proposed, which is capable to tackling effectively statistical simulations of surface segregations in disordered and ordered alloys.</p><p>The applications of relativistic methods include calculations of spin and orbital magnetization in iron-cobalt disordered and partially ordered alloys, as well as computation of the core-level shifts (CLS) in transition metal alloys. It has been found, that relativistic corrections are important for CLS calculations in 5-d metal alloys. Properties of a Ni monolayer deposited on a Cu surface have been studied. The monolayer is found to be unstable in the top layer, and its magnetization depends greatly on the surface orientation. Two distinct energy levels have been found to exist Co/Cu/Ni trilayers deposited on the (100) Cu surface, which correspond to a completely paramagnetic trilayer and the case when only Ni is paramagnetic.</p><p>Vacancy ordering in substoichometric titanium carbides TiC_x have been simulated. Existence of three ordered phases in the range of carbon concentration x=0.5 ÷1.0 has been revealed and a theoretical phase diagram has been proposed. Surface segregations have been calculated in disordered Ni₅₀Pt₅₀ and Ni₅₀Pd₅₀ as well as in ordered NiPt alloys. Segregation reversal has been observed in the Ni₅₀Pt₅₀ alloy with Pt segregation at the (111) surface and Ni segregation at the (110). In the ordered NiPt alloys segregation behaviour is found to be affected greatly by small deviations from the exact stoichiometric composition in bulk. Surface magnetization in PdV and MoV bcc alloys have been studied. It has been found, that in PdV alloys surface segregations suppress magnetic order at the surface, while in MoV alloys magnetization is substantially enhanced due to the segregation.</p>

The present thesis concerns applications of first principles electronic structure calculations in conjunction with methods of statistical mechanics for simulations of transition metal alloys both in the bulk and at surfaces. A fully relativistic generalization of the exact muffin-tin orbitals (EMTO) method has been developed. The method accurately takes into account spin-orbit coupling and allows one to calculate orbital polarization and magneto-crystalline anisotropy in magnetic systems as well as increasing the range of applicability of the EMTO method to heavy elements. A new direct-exchange Monte Carlo (DEMC) method has been proposed, which is capable to tackling effectively statistical simulations of surface segregations in disordered and ordered alloys. The applications of relativistic methods include calculations of spin and orbital magnetization in iron-cobalt disordered and partially ordered alloys, as well as computation of the core-level shifts (CLS) in transition metal alloys. It has been found, that relativistic corrections are important for CLS calculations in 5-d metal alloys. Properties of a Ni monolayer deposited on a Cu surface have been studied. The monolayer is found to be unstable in the top layer, and its magnetization depends greatly on the surface orientation. Two distinct energy levels have been found to exist Co/Cu/Ni trilayers deposited on the (100) Cu surface, which correspond to a completely paramagnetic trilayer and the case when only Ni is paramagnetic. Vacancy ordering in substoichometric titanium carbides TiCx have been simulated. Existence of three ordered phases in the range of carbon concentration x=0.5 ÷1.0 has been revealed and a theoretical phase diagram has been proposed. Surface segregations have been calculated in disordered Ni50Pt50 and Ni50Pd50 as well as in ordered NiPt alloys. Segregation reversal has been observed in the Ni50Pt50 alloy with Pt segregation at the (111) surface and Ni segregation at the (110). In the ordered NiPt alloys segregation behaviour is found to be affected greatly by small deviations from the exact stoichiometric composition in bulk. Surface magnetization in PdV and MoV bcc alloys have been studied. It has been found, that in PdV alloys surface segregations suppress magnetic order at the surface, while in MoV alloys magnetization is substantially enhanced due to the segregation.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-09-19T12:34:19Z No. of bitstreams: 1 RENATO ALEXANDRE COSTA DE SANTANA - TESE (PPGEP) 2007.pdf: 1305574 bytes, checksum: dc82ff3b4b2b221c717f5c4852a6e354 (MD5) / Made available in DSpace on 2018-09-19T12:34:19Z (GMT). No. of bitstreams: 1 RENATO ALEXANDRE COSTA DE SANTANA - TESE (PPGEP) 2007.pdf: 1305574 bytes, checksum: dc82ff3b4b2b221c717f5c4852a6e354 (MD5) Previous issue date: 2007-02-01 / CNPq / Para o estudo dos depósitos binários e ternários, de acordo com a classificação de Brenner, o sistema de Co-Mo e Ni-Co-Mo são considerado como uma codeposição do tipo induzida uma vez que a eletrodeposição do molibdênio a partir do seu estado puro em solução aquosa não é possível de realizar, sendo depositado apenas na presença de um indutor, geralmente um metal do grupo do ferro. Na tentativa de resolver ou amenizar os problemas ligados à eletrodeposição das ligas de molibdênio contendo cobalto e níquel, foi feito um estudo sobre a influência dos parâmetros de operação na eficiência de deposição e da resistência a corrosão da liga binária Co-Mo e da liga ternária Ni-Co-Mo. Os filmes foram eletrodepositados sobre um substrato de cobre com área superficial de 8 cm2. O anodo consistia de uma malha cilíndrica de platina. Para a otimização do processo de eletrodeposição das ligas foi realizado um planejamento fatorial completo. Através do processo de eletrodeposição foram obtidos depósitos das ligas Co-Mo e Ni-Co-Mo de boa qualidade que apresentou boa aderência e brilho. De acordo com os resultados obtidos pelas curvas de polarização potenciodinâmica linear e pelos diagramas de espectroscopia de impedância eletroquímica a liga Ni-Co-Mo poderá ser uma boa alternativa para a substituição do cromo duro utilizado comercialmente com relação a resistência a corrosão. A liga Co-Mo não possui boa resistência à corrosão quando comparado com o cromo e a liga ternária Ni-Co-Mo. Mostrando dessa forma que as ligas ternárias podem ser uma boa alternativa para revestimento contra corrosão. / For studying the binary and ternary deposits, according to the classification by Brenner, the Co-Mo and Ni-Co-Mo systems are considered as an induced type of codeposition since the electrodeposition of molybdenum from its pure state in aqueous solution is not possible to realize, being deposited only in presence of an inductor, generally an iron group metal. With an objective of resolving or decreasing the problems related to electrodeposition of molybdenum alloys containing cobalt and nickel, a study was performed on influence of the operational parameters on the deposition efficiency and corrosion resistance of Co-Mo binary alloy and Ni-Co-Mo ternary alloy. The films were electrodeposited on a copper cathode of about 8 cm2 surface area. The anode was made up of cylindrical platinum gauze. A complete factorial design was applied for optimization of the electrodeposition process. A good quality of Co-Mo and Ni-Co-Mo alloys were obtained by the electrodeposition process, which presented a good adherence and luster. According to the results obtained by potentiodynamic linear polarization curves and spectroscopy electrochemical impedance diagrams, the alloy Ni-Co-Mo could be a good alternative for substitution of the commercially used hard chrome for corrosion resistance. The electrodeposited Co-Mo alloy did not show good corrosion resistance as compared to that of the chrome and of the ternary alloy, Ni-Co-Mo. It showed that the ternary alloy could be a good alternative as corrosion resistant coating.