Microstructure and Mechanical Behavior of Al-Si-Mg Alloys reinforced with TiB_2 particles

摘要

MMCs of aluminum alloy matrix reinforced with TiB_2 particles were prepared in the laboratory by following a powder metallurgy route. The mixture of powders was compacted and, after lubrication, hot extrusion was employed as consolidation process. A homogeneous distribution of the reinforcement particles was achieved. Different studies were carried out in the composites developed.During fabrication and posterior heat treatments of MMCs, it is possible that reaction products and intherphases can appear in case the matrix is a high strength heat-treatable alloy. The effects of the TiB_2 reinforcements on the reactivity layer formation of TiB_2/6061 Al metal matrix composites (MMCs) was investigated. In order to evaluate possible reaction products and intherphases between the matrix and reinforcement, heat treatments regarding temperature (of 350, 400, 450 and 500 deg C) were carried out at a fixed time. Tests were developed as much in MMCs fabricated as in aluminum matrix, to evaluate the changes due to the presence of reinforcement. In this study, optical and scanning electron microscopy with X-ray microanalysis, were used to determine the possible reaction products in the matrix/reinforcement interface and its composition. Microhardness tests were carried out on polished samples in order to evaluate the mechanical behavior. It was followed the Vickers microhardness evolution through the reaction layer formed in the different materials studied.Ultimate strength and strain to failure were studied. There were performed mechanical tests at room temperature and at high temperature of the material in extrusion state. The type of damage was analyzed by scanning electron microscopy, viewing the effect in the sample surfaces. It was considered the microstructures changes due to the strain which samples were exposed. With this aim, longitudinal cuts in the strain were made examined by scanning electron microscopy.