AA7075 aluminum alloy is widely used for several high-technology applications for its high mechanical strength to weight ratio but is still the subject of several studies seeking a further increase in its mechanical properties. A commercial powder is used, either as-received or after ball-milling. Dense AA7075 samples are prepared in one step by Spark Plasma Sintering, at 550 °C with a holding time of 15 min and a uniaxial pressure of 100 MPa. No additional heat treatment is performed. Laser granulometry, X-ray diffraction and optical- and scanning electron microscopy show that both grain size and morphology are preserved in the dense samples, due to the relatively low temperature and short sintering time used. The samples prepared using the ball-milled powder exhibit both higher Vickers microhardness and transverse fracture strength values than those prepared using the raw powder, reflecting the finer microstructure.

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The reuse of industrial waste, such as electric arc furnace dust (EAFD) as reinforcement in aluminum matrix composites (AMC), is still little explored even though it has shown potential to improve the mechanical properties, such as hardness and mechanical strength, of AMCs. To propose a new alternative for EAFD recycling, AA7075-EAFD composites were produced by spark plasma sintering (SPS). The starting powders were prepared by high-energy milling with different weight fractions of EAFD in two particle size ranges added to an AA7075 matrix. SEM shows that the distribution of reinforcement particles in the matrix is homogeneous with no agglomeration of the particles. XRD patterns of initial powders and the SPS-sintered (SPSed) samples suggest that there was no reaction during sintering (no additional peaks were detected). The relative density of all SPSed samples exceeded 96.5%. The Vickers microhardness of the composites tended to increase with increasing EAFD content, increasing from 108 HV (AA7075 without reinforcement) up to 168 HV (56% increase). The maximum microhardness value was obtained when using 15 wt.% EAFD with a particle size smaller than 53 μm (called G1), showing that EAFD presents a promising potential to be applied as reinforcement in AA7075 matrix composites.

This work aimed to obtain a composite material WCuNi using the powder metallurgy. This composite is usable as material for the attenuation of gamma radiation (γ). The tungsten (W) is the main shielding element in this composite. The tungsten has high density (19.25 g.cm -3 ), high melting point (3,422 °C) and is presented as matrix of the composite. In order to meet the need for sintering with temperatures below 1,200 °C, the liquid phase sintering technique was used. For preparation of the samples, shape and size of the particles of the metal powders were analyzed. With the intention of homogenize the distribution of the metallic powders and to reduce the average particle size, a ball mill was used for 24 hours. After grinding, the particle size analysis showed that the mean particle size in WCuNi composition was 12 μm. The powder mixture was compacted in isostatic press at 200 MPa pressure. The samples were sintered at 1,100 °C and at 2,100 mbar pressure of reducing atmosphere (H2) for 8 hours. The formation of the isomorphic system CuNi is responsible for giving the mechanical characteristic of solid to the composite WCuNi. Optical and electronic microscopy (SEM) with EDS were undertaken to characterize the samples. The classical scientific method of experimentations with gamma radiation of the cobalt-60 source by attenuation of the energies was employed to study the effects on the samples. For the energies of 1,173 MeV and 1,332MeV the experimental method indicated the necessity of 11.95 mm of thickness for the solid compound W8Cu1Ni with the obtained density of 11.46 g.cm -3 to attenuate the energy to level allowed for occupationally exposed persons. The experimental values obtained were compared with values calculated by XCOM software database (NIST) of 12.45 mm and convergence of values was observed. Keywords: gamma ray attenuation, powder metallurgy, characterization. ResumoEste trabalho teve como objetivo obter um material metálico (WCuNi) por metalurgia do pó, para determinação do coeficiente de atenuação da radiação gama (γ). O tungstênio (W) é o principal elemento de proteção neste composto, com alta densidade (19,25 g.cm-3), alto ponto de fusão (3.422 ° C) e está presente como matriz do composto. Para atender a necessidade de sinterização com temperaturas inferiores a 1.200 ° C, foi utilizada a técnica de sinterização em fase líquida. Para a preparação das amostras de compostos, a forma e o tamanho das partículas dos pós metálicos foram verificados. Para homogeneizar a distribuição dos pós metálicos e reduzir o tamanho médio de partícula, utilizouse um moinho de bolas durante 24 horas. Após a moagem, a análise do tamanho de partícula mostrou que o tamanho médio de partícula na composição de WCuNi era de 12 μm. Para obter o verde compactado foi aplicado 200 MPa sob pressão isostática. As amostras foram sinterizadas a 1.100 ° C e 2.100 mbar de pressão na atmosfera de redução (H2) durante 8 horas. A formação do sistema isomórfico CuNi é responsável por dar características mecânicas sólidas ao ...