Tratamento térmico de envelhecimento artificial e avaliação do comportamento mecânico e de condutividade elétrica de uma liga AA2024

Abstract

On this paper the mechanical behavior and electrical conductivity of an aluminum alloy 2024 (AA2024) during an artificial aging process was evaluated. The AA2024 alloy is hardenable by the artificial aging process because it has copper and magnesium as alloying elements, which have an increase in their solubility with increasing temperature. It is possible to obtain alternative mechanical properties by selecting the parameters of the aging heat treatment. The main feature of the AA2024 alloy with a Cu:Mg ratio of 2.95 during artificial aging is the formation of Sphase hardening precipitates (Al2CuMg). The material used in this work consists of an AA2024T3 alloy, in a cylinder format, 150 mm long and 19.05 mm in diameter. This material was cut into 12 samples approximately 5 mm thick. The samples were artificially aged according to the following parameters: solubilization at 493°C for 55 minutes, quenching in water at room temperature and aging at 188°C for 10 hours. The effect of the heat treatment on the alloy was analyzed using two different methodologies, for different aging times (0h, 2h, 4h, 6h, 8h and 10h): mechanical (Vickers microhardness) and electroanalytical (electrical conductivity). The results obtained for hardness allowed the construction of a characteristic curve of artificial aging, representing the phase of rapid hardness increase, with a peak hardness time of around 4 hours and (159 ±1%) HV, and subsequent overaging with the decrease in hardness. The electrical conductivity tests allowed a complementary understanding of the precipitation mechanism, suggesting an electron dispersion effect during the underaging and superaging states, causing a decrease in electrical conductivity. An increase in electrical conductivity to (35,2 ±0,07%) %IACS was observed in the phases where the distribution of the precipitates was considered ideal.