Utilização do planejamento de experimentos para análise da influência do ferro no processamento de cavacos da liga 7075 via moagem de alta energia e metalurgia do pó

Abstract

Aluminum alloys are widely used in the aeronautical, automobile, construction and consumer goods industries, mainly due to their low density and high resistance to corrosion. Research aimed at recycling and reuse has increased over the years, and is within SDG objectives 9 and 12. However, one of the greatest difficulties encountered during recycling is the impurity of the iron element, which when present forms phases rich in this element, which are coarse and harmful, which impair the mechanical properties. Therefore, this work aims to analyze the effect of different iron contents on the density and microhardness of alloy 7075 produced by the high-energy grinding/powder metallurgy process from chips. For this, 7075-T6 alloy chips were ground for 40 hours at 400 rpm, then sieved and mixed in a mill for 2 hours at 250 rpm with 2, 4 and 6% by weight of iron. For compaction, values of 400 MPa and 700 MPa were used in a uniaxial press and 250 MPa in an isostatic press, while the sintering time used was 60 and 120 minutes for temperatures of 500°C and 600°C. The density and microhardness results were measured and analyzed using the planning of experiment (DOE) in the Minitab® software, through which it was possible to verify the optimal parameters for each iron addition condition and create mathematical formulas for the density and microhardness, as well how to evaluate the effect of each parameter on the responses. The best sample was produced with the addition of 4% iron, pressure of 700 MPa in the uniaxial press and 250 MPa in the isostatic press, the temperature and sintering time used were 600°C and 60 minutes respectively, with this condition obtaining an average microhardness. of 107.5 HV and density of 2.58 g/cm3.