Estudo do efeito da vibração mecânica na solidificação da liga de alumínio 356.0

Abstract

The vibration on the solidification of aluminum alloys results in grain refining, more homogeneous microstructure and also contributes to degas. The objective of this paper is to evaluate the effects of mechanical vibration on the properties of 356.0 aluminum alloy during solidification by comparing mechanical tests and microstructure analysis of samples obtained with different vibration parameters. A "Y" shaped metal mold was made and supported on a metal base, which was coupled to the pneumatic vibration device. The metal alloy was obtained adding Si and Mg to the pure aluminum in the necessary quantities to the alloy 356.0. The melting occurred in a crucible type oven with a casting temperature of 740 ºC. Three samples were obtained, and the solidification occurred non-vibrated, vibrated with 1 and 2 bar pressure. Seven cylindrical test specimens were made according to ASTM B557M-10 in each sample for tensile tests, Rockwell F hardness, metallography and SEM. The tensile test showed that there was a 6.2% increase in the tensile strength of the vibrated sample with 2 bar pressure (163 MPa) over the non-vibrated (137 MPa) and about 12.5% of the maximum value quoted in standard (145 MPa) for the conventional process. The hardness test showed a 12.9% increase in the results of the sample vibrated with 2 bar pressure (62 HRF) versus non-vibrated (54 HRF). The sample obtained with 1 bar pressure had slightly better results than the non-vibrated sample, and both had surface porosity. The analysis of the microstructure showed that there was a change of the microstructure and the grains became more round as the vibration intensity increased.