Propriedades mecânicas de alumínio sinterizado em micro-ondas com reforço de esferas de carbono ou partículas de vidro

Abstract

Aluminum is a material widely studied and used in the most varied projects and sectors of the economy due to a set of interesting properties that attribute to this material, ease in machinability, casting and even recycling processes. Powder metallurgy is a very efficient methodology used both in the production of aluminum composites, aiming to obtain significant mechanical properties that can meet the various applications required by the industry, such as high values of hardness, modulus of elasticity and resistance limit. Researchers have been studying both the insertion of reinforcement materials and alternative methodologies for the sintering of aluminum powder-based products, in order to control their mechanical properties. The great challenge is to achieve this objective using methodologies that are sustainable and friendly to the environment. In this context, focusing on the reuse of tailings and residues from discarded materials, reinforcement materials obtained from glass particles, produced by grinding discarded glassware in laboratories and/or carbon microspheres, produced from coconut fiber waste. The use of these reinforcements in the production of aluminum-based composites, using powder metallurgy and microwave sintering, becomes a highly promising alternative. Thus, in this work, the microwave sintering method was used to produce aluminum matrix-based composites containing borosilicate glass particle reinforcements and carbon microspheres, produced from coconut fiber by the microwave-assisted hydrothermal method. . The reinforcement materials, in proportions that varied between 0.1 and 10.0% by mass, were mixed with pure commercial aluminum powder, using a conventional pitcher mill. The carbon spheres used had an average diameter of 4.0 µm and the average diameter of the glass powder particles was 8.9 µm. The study on the optimization of the time used for the mixtures of aluminum powders to carbon sphere powders (AL-EC) and, aluminum powders to glass particle powders (AL-PV) were carried out, revealing that the mixture made in a horizontal ball mill, dry, for 9 hours leads to obtaining the most homogeneous mixtures. The powders obtained from the mixtures, AL-EC and AL-PV, were compacted, by uniaxial pressing, in the shape of discs using a metallic matrix. Subsequently, the discs were sintered at 600ºC for 60 minutes in a microwave oven. For comparative studies, samples of pure aluminum were sintered in microwave under the same conditions as the samples containing the reinforcements, and were sintered in a conventional oven. Densification measurements, as well as X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) analyzes were performed on the studied samples. The characterization of the mechanical properties was carried out by means of microhardness measurements and tests of flexural strength, or transverse rupture (TRS). The pure AL samples showed a microhardness of 65.50 HV and TRS of 103.4 Mpa. The AL-PV and AL-EC samples showed improvements in their mechanical properties compared to pure aluminum. The samples containing 1% of glass powder reinforcement had a microhardness of 99.29 HV and a flexural strength of 105.0 MPa, while the samples containing 1% of carbon spheres had a microhardness of 75.52 HV and flexural strength. of 82.3 MPa, obtaining important changes in the mechanical properties of the composites produced.