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Carbon nanotubes (CNTs) were dispersed by mechanical milling into a 2024 aluminum alloy (Al 2024 ) in order to produce composites and study the influence of CNTs content over the mechanical and microstructural behavior of them. The time of milling was set to 5 h [1] and the addition of CNTs was of 0.0 to 5.0 wt. %. Powders obtained from milling process were cold compacted and then sintered under argon atmosphere by 2h with 5ºC/min for heating and cooling rates. The microstructural analysis was carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). In the other hand, their mechanical performance was evaluated by microhardness Vickers. Microhardness values from several aluminum commercial alloys reported in literature were compared with these experimental results.CNTs used as material reinforced are shown in Figs. 1(a,b). Diameters of ~80 nm and lengths of ~0.8 mm were observed. Fig. 1c displays the microstructure after sintering process. It can be observed a well dispersion Al 2 Cu phase produced by low cooling rate in sintering treatment. Figs. 1 (d,e) present bright field TEM micrographs from the composites with 1.0 and 5.0 wt.%, respectively. CNTs are observed in Fig. 1f from the composite with 1.0 wt.% of nanotubes. A second phase characterized as Al 4 C 3 is shown in Fig. 1g. Fig. 2a shows the results from XRD of the Al 2024 -CNTs composites as a function of the CNTs content. An increase in the peaks intensity attained to the aluminum carbides (Fig. 1e, marked with circles, and 1g) is observed as function of the CNTs content. However no variation was observed for the Al 2 Cu intensity peaks. The presence of CNTs after milling process and sintering heat treatment was verified by TEM as is shown in Fig. 1g.The mechanical characterization of the composites indicates that a rapid increament in mechanical properties is observed as a function of the addition of the CNTs (Fig. 2b). The maximum Vickers hardness value (219.74 VHN) observed in this work was reached by the sample with 5.0 wt.% of CNTs, this value represents ~346% (170.56 hardness units) over the pure Al hardness value. The composite with 3

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In this work, the mechanical properties and microstructural features of an AISI 304L stainless steel in two presentations, bulk and fibers, were systematically studied in order to establish the relationship among microstructure, mechanical properties, manufacturing process and effect on sample size. The microstructure was analyzed by XRD, SEM and TEM techniques. The strength, Young’s modulus and elongation of the samples were determined by tensile tests, while the hardness was measured by Vickers microhardness and nanoindentation tests. The materials have been observed to possess different mechanical and microstructural properties, which are compared and discussed.

Aluminum nanocomposite was obtained through mechanical alloying process using elemental powders of aluminum, copper and magnesium of high purity with the aim to obtain the 2024 aluminum alloy composition. Elemental powders and reinforcement particles were milled in a simoloyer mill for different times from 1 to 5 h. X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) results indicated that even for milling time of 5 h some elemental copper remained in the microstructure and has not been incorporated completely in solid solution into the aluminum lattice. Furthermore, it was not observed formation of any second phase, however when the specimens were subjected to Differential Thermal Analysis (DTA), it was observed in the microstructure the presence of Al 2 Cu, Al 4 C 3 and some oxide of the type CuO and CuO 2 . It was also demonstrated that average crystallite size of milled powders was refined to nanometric level while microhardness values were arising continuously with the milling time and were a maximum in the 2 mass% graphite specimen.