Investigation of the effect of boron carbide nanoparticles on the structural, electrical and mechanical properties of Al-B4C nanocomposites

Abstract

Aluminum is widely used in the electrical, automotive, transport and aerospace industries due to its remarkable properties, such as low density and relatively low costs. However, due to the low hardness and low yield strength, there are limitations in application of aluminum. To solve these limitations, aluminum is made with other hard materials in the form of nanocomposites. For this purpose, in this work, using B4C nanoparticles, Aluminum-boron carbide nanocomposites (Al-B4C) nanocomposites were prepared via ball milling processing. The ball milling process was carried out at room temperature under argon atmosphere using a planetary ball milling for 10 h at 300 rpm. The B4C nanoparticles content employed in these nanocomposites were 0, 5 and 10 wt%. To investigate the structural, mechanical and electrical properties of the Al-B4C nanocomposites, the powders were pressed and then sintered under argon atmosphere at 650 °C. The structure, density, hardness and electrical conductivity of the Al-B4C nanocomposites sintered tablets were investigated by X-ray Diffraction (XRD), Field Emission Scanning Electron microscopy (FESEM) with energy dispersive x-ray spectroscopy (EDS), Archimedes method, nanoindentation and eddy current test, respectively, and the results are discussed. The XRD patterns confirmed the presence of aluminum and B4C and the lack of any interphase and secondary phase in the Al-B4C nanocomposite. Distribution of B4C nanoparticles in Al-B4C nanocomposite was described via EDS assisted elemental mapping images. Moreover, with the addition of 5 and 10%wt. B4C nanoparticles in aluminum matrix, the hardness values of the Al-B4C nanocomposites was measured to be 138HV and 172HV which were higher than 67HV for the pure aluminum, respectively. Consequently, nanoindentation analysis showed that the hardness of Al-B4C nanocomposites was better than that of pure aluminum. Density values of Al-B4C nanocomposites were measured to be 2.5776 g/cm3 and 2.4949 g/cm3 which were lower than 2.6346 g/cm3 for the pure aluminum, respectively. Electrical conductivity of Al-B4C nanocomposites was measured to be 23%IACS and 13%IACS which were lower than 39% IACS for the pure aluminum, respectively. To evaluate the effect of particle size on the properties of Al-B4C composites, under the same conditions of Al-B4C nanocomposites preparation, Al-B4C microcomposites were prepared. With increasing B4C content, the hardness of Al-B4C nanocomposites were obtained higher than those for Al-B4C microcomposites. This behavior has been explained by Hall–Petch Model and Orowan strengthening. The density of the Al-B4C nanocomposites was obtained higher than those for Al-B4C microcomposites and the electrical conductivity of Al-B4C nanocomposites less than the resulting for Al-B4C microcomposites.