Mo-Si-B alloys are a leading candidate for the next generation of jet turbine engine blades and have the potential to raise operating temperatures by 300-400°C. The alloys of interest are a three-phase mixture of the molybdenum solid solution (Moss) and two intermetallic phases, Mo3Si (A15) and Mo5SiB2 (T2). A novel powder metallurgical method was developed which uses the reaction of molybdenum, silicon nitride (Si3N4) and boron nitride (BN) powders to synthesize a fine dispersion of intermetallics in a Moss matrix. The covalent nitrides are stable in oxidizing environments up to 1000ºC, allowing for fine particle processing. The process developed uses standard powder processing techniques to create Mo-Si-B alloys in a less complex and expensive manner than previously demonstrated. This powder metallurgy approach yields a fine dispersion of intermetallics in the Moss matrix with average grain sizes of 2-4μm. Densities up to 95% of theoretical were attained from pressureless sintering at 1600°C and full theoretical density was achieved by hot-isostatic pressing (HIP). Sintering and HIPing at 1300°C reduced the grain sizes of all three phases by over a factor of two. Microstructure examination by electron back-scatter diffraction imaging was used to precisely define the location of the phases and to measure the volume fractions and grain size distributions. Microstructural quantification techniques including two-point correlation functions were used to quantify microstructural features and correlate the BN reactant powder size and morphology to the distribution of the intermetallic phases. High-temperature tensile tests were conducted and yield strengths of 580MPa at 1100°C and 480MPa at 1200°C were measured for the Mo-2Si-1Bwt.% alloy. The yield strength of the Mo-3Si-1Bwt.% alloy was 680MPa at 1100°C and 420MPa at 1300°C. A review of the pertinent literature reveals that these are among the highest yield strengths measured for these compositions. The oxidation resistance in air at 1000 and 1100°C was examined. The protective borosilicate surface layer formed quickly due to the close spacing of intermetallic particles and pre-oxidation treatment was developed to further limit the transient oxidation behavior. An oxidation model was developed which factors in the different stages of oxidation to predict compositions that minimize oxidation.

M. Tech. (Department of Metallurgical Engineering, Faculty of Engineering Technology), Vaal University of Technology. / This work is an investigation in the development and characterisation of porous Ti-Sn-SiC and Ti-Nb-SiC composites. Pure Titanium (Ti), Tin (Sn), Niobium (Nb) and Silicon carbide (SiC) powders were used as starting materials. The Ti-Sn-SiC and Ti-Nb-SiC composites were produced by powder metallurgy (PM) press-and-sinter route. The Sn is an α-phase stabilizer while Nb is a β-phase stabilizer in Ti alloys. A systematic study of binary Ti-Sn and Ti-Nb alloys was conducted with the addition of SiC particles. The addition of Sn influences the microstructure of the titanium alloy. With increasing the percentage of Sn content, the density of the samples decreases on the Ti-Sn alloys. An increase in the Sn content from 10 to 25 wt. % content resulted in decreased hardness. The Ti-Sn binary revealed stability of the HCP phase with increasing composition of the Sn content. The porous structures of the Ti-Sn-SiC composites were evenly distributed throughout the materials. The sintered densities increase from 94.69% to 96.38%. XRD analysis detected the HCP crystal lattice structure for the Ti5.4Sn3.8SiC and Ti5.6-Sn3.8-SiC composites. XRD pattern of the Ti5.8-Sn3.8-SiC reveals both the HCP and FCC crystal structures. The HCP phase has lattice parameters a= 2.920 Å; c=4.620 Å with smaller c/a ratio of 1.589. Additionally, FCC lattice parameter a=5.620 Å Fm-3m # 225 was obtained both for Ti5.8Sn3.8SiC and Ti6.0Sn3.8SiC XRD patterns. On the other hand, Optical microscopy analysis of the Ti-Nb alloys revealed the equiaxed grains composed of the light β-phase segregating on the grain boundaries. The Ti9Nb1 has low Vickers hardness of all alloys while Ti8Nb2 and Ti7.5Nb2.5 alloys are harder due to high amount of Nb content. Generally, the densities of the Ti–Nb alloys increased with increasing Nb content. HCP and BCC phases have the lattice parameters a = 2.951 Å, c = 4.683 Å and 3.268 Å, respectively. An HCP (α′) phase was detected in the Ti8.5Nb1.5 alloy with lattice parameters a = 5.130 Å, c = 9.840 Å while a BCC phase had a = 3.287 Å. The sintered Ti8Nb2 alloy also had the α′-phase with a = 5.141 Å, c = 9.533 Å and BCC phase with a = 3.280 Å lattice parameters. On the contrary, the Ti7.5Nb2.5 alloy formed the α′-phase of a = 5.141 Å, c = 9.533 Å and BCC with a = 3.280 Å lattice parameters. For the 10 and 15 wt.% Nb alloys, very porous structures were observed. The pores appear spherical and widely distributed. As the Nb content is increased to 20 wt.% (Ti7Nb2SiC) and 25 wt.% (Ti7Nb2.5SiC), porosity was minimized. The sintered densities of the Ti-Sn alloys are decreasing from 95.90% to 92.80% with increased amount of Sn in the Ti, while the sintered densities of Ti-Sn-SiC are increasing from 94.69% to 96.38%. The high porosity, which developed in Ti7Nb1SiC and Ti7Nb2.5SiC, affected the densities of these composites. The sintered densities of Ti-Nb alloys are increasing from 92.08% to 97.65% with increased amount of Nb in the Ti. In terms of hardness Ti7Nb1SiC and Ti7Nb2.5SiC resulted in the lowest while Ti7Nb1.5SiC and Ti7Nb2SiC composites were 511.74 HV and 527.678 HV. The porosity levels were increased by the addition of SiC in the Ti-Sn-SiC and Ti-Nb-SiC composites. The XRD analysis revealed phase transformation on the Ti-Nb alloys and Ti-Nb-SiC composites.

The development of molybdenum - silicon - boron (Mo-Si-B) composites having a combination of high temperature strength, creep, and oxidation residence has the potential to substantially increase the efficiency of gas turbines. The refractory nature of the αMo, Mo3Si (A15), and Mo5SiB2 (T2) phases results in good strength and creep resistance up to 1300°C. At this temperature, the formation of a borosilicate surface scale from the two intermetallic phases is able to provide oxidation resistance. However, realization of these advantages has been prevented by both a high brittle to ductile transition temperature and difficulty in forming the initial surface borosilicate to provide bulk oxidation resistance. This dissertation addresses two factors pertaining to this material system: 1) improvements to powder processing techniques, and 2) development of compositions for oxidation resistance at 1300°C. The processing of Mo-Si-B composites is strongly tied to their mechanical properties by establishing the αMo matrix, limiting impurity content, and reducing silicon supersaturation. These microstructural aspects control the brittle to ductile transition temperature which has traditionally been too high for implementation of Mo-Si-B composites. The processing here built upon the previously developed powder processing with silicon and boron nitrides which allowed for a low oxygen content and sintering of fine starting powders. Adjustments were made to the firing cycle based upon dew point measurements made during the hydrogen de-oxidation stage. Under a relatively high gas flow rate, 90% of the total water generated occurred during a ramp of 2°C /min between 450 and 800°C followed by a hold of 30 minutes. The oxidation resistance of Mo-Si-B composites was studied for a wide range of compositions. Silicon to boron atomic ratios were varied from 1 to 5 and iron, nickel, cobalt, yttria, and manganese were included as minor additions. In all these compositions, the αMo volume fraction was kept over 50% to ensure the potential toughness of the composite. For the oxidized surface glass, a silica fraction of 80 to 85% was found to be necessary for the borosilicate to have a sufficiently high viscosity and low oxygen permeability for oxidation resistance at 1300°C. For the Mo-Si-B bulk composition this corresponds to a Si/B atomic ration of 2 to 2.5. Higher viscosity compositions failed due to spallation of poorly attached, high silica scales. Lower viscosity compositions failed from continuous oxidation, either through open channels or repetitive MoO3 bubble growth and popping. Additionally, around 1% manganese was necessary for initial spreading of the borosilicate at 1300°C. In conjunction with flowing air to prevent MoO3 accumulation, oxidation weight loss rates below 0.05 mg/cm2-hr were measured. Finally, a theory is proposed here to describe the mechanisms responsible for the development of oxidation resistance. This theory involves three stages associated with: 1) generation of an initial surface borosilicate, 2) thickening of the borosilicate layer, and 3) slow parabolic oxidation controlled by the high silica surface scale.

<p>Bioresorbable iron-manganese (Fe-Mn) alloys are considered as a new class of biomaterials for the development of orthopedic fixation devices due to their promising mechanical properties, comparable to the human cortical bone, and the ability to degrade in the physiological environment and release small quantities of metallic ions/particles that are absorbable by the host. The greatest challenge for developing an ideal resorbable Fe-Mn alloy is to increase the degradation rate of the alloy without compromising the alloy biocompatibility, that is, causing zero or minimal local and systemic toxicity to the tissue. Another challenge is to improve osteo-integration through inducing a cascade of events leading to tissue ingrowth.</p> <p> </p> <p>The incorporation of porosity into the Fe-Mn alloys aimed to increase the corrosion rate and to provide the three-dimensional structure for cellular activity and nutrient transport. The Fe-30wt.%Mn alloys with 0-, 5-, 10-, and 60-volume percent porosity were produced through the space holder technique in powder metallurgy. The space-holder material, ammonium bicarbonate (NH₄HCO₃), was sieved to a particle size ranging 355~500 µm. The microstructures and mechanical properties of the alloys, as well as the influence of the degree of porosity on the alloy corrosion rates comparing to the concentrations of the degraded metal ions were investigated. Although the Fe-30Mn alloys containing 60-vol% porosity exhibited the lowest average ultimate compressive strength of 381 MPa among the tested groups, they were still mechanically stronger than a typical human wet compact bone. Furthermore, the alloys had the highest average corrosion rate of 0.98 ± 0.20 mm/year, compared to 0.13 ± 0.07 mm/year for the non-porous Fe-30Mn alloys. Nevertheless, the extract from the 60%-pore group had a cytotoxicity effect to the bone marrow stem cells (BMSCs) at an average normalized cell viability of 58%, which was below the standard viability of 70%, considered as cytotoxic in the indirect cytotoxicity study. The cytotoxicity study also corresponded to the highest level of transition metal ions Mn²⁺ released into the media for the 60%-pore group at an average ion released rate of 7 mg/day, compared to the other groups presenting similar Mn²⁺ released rates about 4 mg/day after 1 day of incubation. The extreme case of the 60%-pore group demonstrated the tradeoff between the corrosion rates and biocompatibility. On the other hand, the 10%-pore group showed an average ultimate compressive strength of 737 MPa comparable to the stainless steel 316L, an average corrosion rate of 0.260 ± 0.09 mm/year, which was 2-fold higher than the non-porous group, and an average cell viability of 86% close to the non-porous group. It is promising based on the above results, however, the osteo-integration of the 10%-pore group in terms of cell-to-cell and alloy-to-cell interactions was not ideal. </p>

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Doctor of Philosophy.‘ Johannesburg, August 2017 / Fe-B-C composites were produced, from boron carbide and iron powders, using spark plasma sintering. This provided information on the effects of rapid sintering on densification, composition and the microstructure of the materials produced. The composition range included a selection high Fe contents (69.3, 78 and 80.9 vol. % Fe-B4C) and high B4C concentrations (1, 3, 5 vol. % Fe-B4C). The properties of the materials were investigated to determine the potential for using relatively cheap Fe and B4C powders to produce hard, wear resistant materials. High Fe-B4C composites were sintered at 900, 1000 and 1100°C at 60 MPa. Densification increased with increasing temperature and at 1100° each composition achieved ≥ 97 % densification. The materials reacted during sintering with the main phases observed being Fe2B and Fe3(B,C) whilst additional phases formed were FeB, C and Fe23(B,C)6.Comparing the phases that were produced to Fe-B-C phase diagrams showed deviations from expected compositions, indicating the non-equilibrium nature of producing the composites using SPS. Although the composites were not at equilibrium, all the B4C reacted and could not be maintained, even with fast heating and cooling rates. The properties of the materials were dependent on both densification and the phases that were present after sintering. Materials containing higher amounts of the Fe2B phase showed higher hardness and fracture toughness results, up to 13.7 GPa and 3.5 MPa.m0.5 respectively for the 69.3 vol. % Fe-B4C. The materials were sensitive to grain and pore growth which negatively affected properties at 1100°C. The transverse rupture strength of 388.3 MPa for 80.9 vol. % Fe-B4C composite was the greatest, and showed evidence of both intergranular and transgranular fracture. The strength was affected by a fine dispersion of porosity at the grain boundaries, throughout the material, and free carbon in the structure was detrimental to the strength of the 69.3 % Fe-B4C. The wear rates were lower using Si3N4 wear balls compared to stainless steel balls, where 69.3 vol. % Fe-B4C showed the best wear rates, 8.9×10-6 mm3/Nm (stainless steel ball) and 1.77×10-6 mm3/Nm (Si3N4 ball), due to the higher Fe2B composition and free carbon acting as a lubricant during sliding. 1, 3 and 5 vol. % Fe-B4C composites were sintered to densities above 97 % of theoretical at 2000°C and 30 MPa. The formation of a transient FeB liquid phase assisted densification. 1 % Fe-B4C attained hardness and fracture toughness up to 33.1 GPa and 5.3 MPa.m0.5 with a strength of 370.5 MPa. Thermal mismatch between the FeB phase and B4C caused high residual stresses at the interface which led to cracking and pull-out of the FeB phase. Residual carbon at the grain boundary interface exacerbated the pull-out effect. Increasing Fe and the subsequent FeB phase had an embrittling effect. The materials suffered severe wear of up to 36.92×10-6 mm3/Nm as a result of the pull-out with the remaining porosity acting as a stress raiser. 20 vol. % of the Fe in each system was substituted with Ti to reduce the presence of residual carbon. Although in some case the properties of the respective compositions improved, residual carbon was still present in the composites. / MT2018

O objetivo deste trabalho foi desenvolver uma forma alternativa de se produzir alvos para irradiação contendo urânio, destinados à produção do par de radionuclídeos 99Mo-99mTc. Estes alvos foram obtidos por metalurgia do pó, utilizando-se pós de níquel e de cobre, servindo o compactado como meio de encapsulamento para um cilindro de urânio a ser irradiado. O desenvolvimento compreendeu as etapas de caracterização química e física dos pós-utilizados. Os alvos foram compactados em prensa uniaxial e em prensa isostática a frio. As amostras foram sinterizadas em três atmosferas diferentes: argônio, hidrogênio e em alto vácuo. Quando do uso conjunto de cobre e níquel, foi feita sinterização por dois corpos, i.e., um compactado de níquel contendo o núcleo para ser irradiado e um compactado de cobre para servir de infiltrante. Isto, visando a eliminação de porosidade interconectada, permitindo o selamento do conteúdo físsil no interior do compactado. Os alvos após sinterização foram caracterizados fisicamente sendo avaliada a massa específica, pelo método geométrico e pelo princípio de Arquimedes. A porosidade foi medida pela técnica de porosimetria de mercúrio. Os alvos prontos foram caracterizados micro estruturalmente por microscopia óptica e eletrônica de varredura. Os resultados indicaram que a densificação do níquel foi diretamente proporcional à pressão de compactação obtendo-se 87% de densidade relativa após prensagem a 800 MPa (limite superior de compactação para ligas metálicas) e sinterização por 4 h a 600 ºC em atmosfera de hidrogênio. A sinterização por dois corpos (níquel com cobre) mostrou-se promissora para o uso como invólucro para núcleos, em termos de integridade estrutural e selamento devido à ausência de porosidade interconectada. / The objective of this work was to develop an alternative way to obtain targets for irradiation, containing uranium, destined for the production of the radionuclide pair 99Mo-99mTc. The targets were obtained using powder metallurgy using nickel and cooper powders, serving the compact as a medium for encapsulation of a uranium cylinder to be radiated. The development started with the chemical and physical characterization of the used powders. The targets were compacted either in uniaxial press and cold press isostatic. The samples were sintered at three different atmospheres: argon, hydrogen and high vacuum. In the case of use of nickel and copper, it was used the two bodies technique for sintering, i.e., a nickel compact containing a core to be irradiated and the cooper used as infiltrant. This was aiming at the elimination of interconnected porosity, allowing the sealing of any fissile content in the interior of the compact. The targets were physically characterized after sintering the density being evaluated by geometrical method and the Archimedes principle. The porosity was measured by the technique of mercury porosimetry. The targets were microstructurally characterized using optical and scanning electronic microscopy. The results indicated that the nickel densification was directly proportional to the compaction pressure yielding 87% relative density after pressing at 800 MPa (upper limit for alloys compaction) and sintering for 4 h at 600 °C in hydrogen atmosphere. Sintering of two bodies (nickel and copper) has shown some feasibility for use as core casing in terms of structural integrity and sealing due to the absence of interconnected porosity.

Existem diversos componentes produzidos por metalurgia do pó que necessitam utilizar uma matéria prima nobre devido a aplicações que causam desgaste em áreas específicas. Desta forma faz-se necessário o desenvolvimento de um material tornando o projeto mais atraente economicamente. O objetivo deste trabalho é analisar e discutir o efeito da densidade nas propriedades mecânicas e microestruturais de materiais com gradiente de função, compostos por metade de ferro comercialmente puro e a outra metade de um material mais nobre, que contém elementos de liga específicos para tratamento de sinterhardening. Corpos de prova foram compactados variando-se a densidade, posteriormente sinterizados e revenidos. Ensaios mecânicos e análise microestrutural foram realizados. Foi possível verificar, de acordo com os resultados, que o aumento da densidade promove o aumento das propriedades mecânicas. Além disso, um pequeno incremento na densidade do componente proporciona a formação do dobro de martensita. Desta forma, é possível fabricar componentes com esta composição levando-se em consideração a distância referente a zona de transição para que as propriedades necessárias estejam presentes nas regiões críticas. / There are several components produced by powder metallurgy that need to use a noble raw material due to applications that cause wear in specific areas. In this way it is necessary to develop a material made the project more economically attractive. The objective of this work is to analyze and discuss the effect of density on the mechanical and microstructural properties of functionally gradient materials composed of half of commercially pure iron and the other half of a more noble material containing specific alloying elements for the treatment of sinterhardening. Test specimens were compacted by varying the density, sintered and tempered. Mechanical tests, metallographic analysis and hardness were performed. It was possible to verify, according to the results, that the increase of the density promotes the increase of the mechanical properties. In addition, a small increase in component density gives the formation of twice martensite.In this way, it is possible to fabricate components with this composition taking into account the distance of the transition zone so that the necessary properties are present in the critical regions.

As ligas de Al-Si são amplamente utilizadas na indústria, recentes avanços possibilitaram a produção de ligas de alumínio com ótimas propriedades podendo-se destacar o seu baixo peso, excelente resistência à abrasão e à corrosão, e baixo coeficiente de expansão térmica em relação ao aço. O objetivo deste trabalho foi avaliar o comportamento da mistura de pós elementares de Cu, Si, Mg, Ni, Fe a uma base de alumínio, sinterizado individualmente em atmosfera controlada com gás argônio e nitrogênio pelo processo de sinterização convencional em forno resistivo. Após realização de análise o composto que forneceu o melhor desempenho foi submetido a um comparativo com amostras sinterizadas via plasma. Os resultados encontrados foram confrontados com os resultados da liga de EN AC- 48000 (AlSi12CuNiMg) fundida, a fim de avaliar os aspectos mecânicos e físicos do composto intermetálico. O desenvolvimento do trabalho se deu a partir do pó de alumínio com pureza de 99,7%, ao qual foi incorporado o percentual dos demais elementos, com base na composição da liga comercial EN AC-48000 (Si12%; Fe0,45%; Cu1,08%; Mg1,08%; Ni1,14%). Após a sinterização as amostras foram caracterizadas quanto a densificação, microdureza e rugosidade superficial, além disso, uma análise metalográfica foi realizada por microscopia óptica, bem como foi feita uma por difração de raios-X para a verificação da formação de novas fases. A densificação das amostras sinterizadas pelo processo convencional com atmosfera controlada por nitrogênio foi superior as produzidas com atmosfera de argônio, ficando também superior ao processo assistido por plasma com nitrogênio. Pelo processo convencional de sinterização a microdureza apresentada pelas amostras obtidas por atmosfera de nitrogênio foi na média superior a encontrada nas amostras produzidas com atmosfera de argônio, já a microdureza apresentada pelas amostras assistida por plasma com atmosfera controlada por nitrogênio, atingiram resultados abaixo da sinterização convencional. Durante o processo de sinterização a plasma, as amostras acabaram sofrendo uma reação abaixo da temperatura de sinterização desejada (510 °C), ocasionando microfusão na superfície da amostra, e logo em seguida deformações. Estas reações tiveram influência direta nos resultados encontrados nas amostras produzidas via sinterização a plasma, desta forma a temperatura teve que ser reduzida. / Al-Si alloys are being used in industry to replace steel and cast iron in high-tech sectors. Recent advances have allowed the production of aluminum alloys with excellent properties, highlighting their low weight compared to steel, excellent resistance to abrasion and corrosion, high resistance at high temperatures and low coefficient of thermal expansion. The objective of this work is to evaluate the behavior of the Cu, Si, Mg, Ni and Fe elemental powder mixtures with an aluminum base, individually sintered in a controlled atmosphere with argon and nitrogen using the conventional sintering process in a resistance furnace. After this process, the best performing compound was submitted to a comparison with plasma sintered samples. The results were compared with those for the EN AC- 48000 (AlSi12CuNiMg) molten alloy, to evaluate the mechanical and physical aspects of the intermetallic compound. The development of the work was based on the 99.7% aluminum powder donated by Alcoa with the addition of other elements from the commercial alloy composition EN AC-48000 (Si12%; Fe0,45%; Cu1,08%, Mg1,08%, Ni1,14%). After sintering, the samples were carachterized by surface roughness, densification, microhardness, optical microscopy and X-ray diffraction analysis. The densification of the sintered samples by the conventional process with the controlled atmosphere by nitrogen gave higher densification values than for samples produced with the argon atmosphere or by the plasma assisted process using nitrogen. By the conventional sintering process, the samples processed in nitrogen atmosphere presented higher hardness values than those produced with argon atmosphere, and also higher than those plasma assisted sintered with nitrogen atmosphere. During the plasma sintering process, the samples underwent a reaction below the desired sintering temperature (510 °C), causing microfusion on the sample surface, and deformations. These reactions had a direct influence on the results found in the samples produced by plasma sintering, therefore the temperature for the plasma process had to be reduced.

O objetivo desse trabalho é analisar a fabricação de buchas a base de Alumínio empregando o processo de Metalurgia do Pó, em substituição ao processo atual de fundição e usinagem. O material testado é uma liga a base de Alumínio AlSi10Cu3, essa liga contem 87% de Alumínio, 10% de Silício, 2,5% de Cobre, 0,25% de Magnésio e Manganês, conforme a norma DIN EN 1706. As amostras foram compactadas à 600MPa, resultado obtido da curva de compressibilidade. As amostras foram sinterizadas a uma temperatura de 550ºC durante 60 minutos. Após sinterização as amostras foram submetidas ao processo de Tratamento Térmico T6, com temperatura de solubilização de 480°C por 5 horas e envelhecimento a 220°C por 5 horas, nomeado Tratamento Térmico A. Foram realizados ensaios de densidade, dureza, metalografia, compressibilidade, difração de raios-x e variação dimensional. A densidade das amostras sinterizadas atingiram 2,52 g/cm3 ± 0,25. A dureza superficial das amostras atingiram uma média de 51 HB ± 4. Com o tratamento térmico T6 a dureza elevou-se para 74 HB ± 2. A variação dimensional das amostras após sinterização foi de 0,20% na área dos corpos de prova. Foram estudadas também diferentes composições químicas para elevar a dureza superficial. Executou-se um teste com outros parâmetros de Tratamento Térmico T6 para aumento da dureza, chamado de Tratamento Térmico B, com parâmetros de temperatura de solubilização de 550°C por 1 hora e envelhecimento com 160°C por 18 horas. / The objective of this work is to analyze the manufacture of aluminum based bushings employing the Powder Metallurgy process in substitution of the current process of casting and machining. The material tested is an AlSi10Cu3 aluminum alloy, this alloy contains 87% aluminum, 10% silicon, 2.5% copper, 0.25% magnesium and manganese, according to DIN EN 1706. The samples were pressed at 600MPa, result obtained from the compressibility curve. The samples were sintered at a temperature of 550°C for 60 minutes. After sintering, the samples were submitted to the T6 Thermal Treatment process, with a solubilization temperature of 480°C for 5 hours and aging at 220°C for 5 hours, named Thermal Treatment A. Density, hardness, metallography, compressibility, X-ray diffraction and dimensional variation testings were performed. The density of the sintered samples reached 2.52 g/cm3 ± 0.25. The surface hardness of the samples reached the mean of 51 HB ± 4. With the heat treatment T6 the hardness increased to 74 HB ± 2. The dimensional variation of the samples after sintering was 0.20% by area. Different chemical compositions were also studied to raise the surface hardness. A test was performed with other parameters of T6 Thermal Treatment to increase the hardness, called Thermal Treatment B, with parameters of solubilization temperature of 550°C for 1 hour and aging with 160°C for 18 hours.

Nesta dissertação, foram estudados materiais com gradiente de função produzidos por metalurgia do pó a fim de se encontrar uma alternativa com redução de custo para aplicações na indústria automobilística. Os corpos de prova produzidos com ferro comercialmente puro e materiais ligados foram ensaiados de maneira a entender o efeito da interface no componente a ser produzido. Foram estudadas as propriedades de ruptura transversal, resistência à tração, macro e microdureza, além da microestrutura por microscopia ótica e microscopia eletrônica de varredura. Foi possível verificar que é uma alternativa viável, mas se faz necessário um controle da posição da interface e do elemento de liga a ser utilizado no material mais nobre a fim de se obter o melhor desempenho do componente. / In this dissertation, materials with a gradient of function produced by powder metallurgy were studied in order to find an alternative with cost reduction for applications in the automobile industry. The specimens produced with commercially pure iron and alloyed materials were tested in order to understand the effect of the interface on the component to be produced. The properties of transverse rupture, tensile strength, macro and micro hardness, as well as, the microstructure by optical microscopy and scanning electron microscopy were studied. It was possible to verify that it is a viable alternative, but it is necessary to control the position of the interface and the alloying element to be used in the noblest material in order to obtain the best performance of the component.