Influência do Si e quasicristal (Al-25,5Cu-12 Fe) na microestrutura de ligas de aluminio reciclado solidificados sob pressão

Abstract

With the development of new multicomponent alloys aimed at improving mechanical properties, the use of recycled aluminum to produce new alloys is becoming a new alternative for the industrial market, in addition to contributing to the reuse of these materials have low cost. Furthermore, to improve the mechanical properties it is necessary to understand the microstructural behavior of the alloys. In view of this, this work aimed to understand the effects of the addition of Si and of a quasicrystalline material (Al 25,5Cu-12Fe) in the microstructural variation of recycled aluminum, as well as its effects on the liquidus isotherm velocity (VL) and the cooling rate (TR) solidified under pressure. Recycled aluminum alloys (Alrec) with the addition of 5%Si and 5%Quasicrystal were produced in a cylindrical mold under 100Mpa pressure with a pressing time of 10 seconds. It was observed that the addition of the elements (Si and Quasicrystal) promoted an increase in the values of the thermal parameters (VL, TR) compared to the recycled Al alloy, i.e., addition of the elements facilitated heat extraction, providing a faster solidification. Differences in the microstructures of the alloys were identified: the recycled Al alloy showed a cellular morphology, however for Alrec-5%Si e Alrec 5%Quasicrystal alloys the microstructure was predominantly dendritic throughout the ingot. Microstructural spacings (λc and λ2) were also observed to decrease with increasing liquidus isotherm displacement velocity and cooling rate. Moreover, in Alrec 5%Quasicrystal alloy it was noted the presence of intermetallics in the central region of the ingot, for being a multicomponent alloy, the formation of intermetallics is directly related to the thermodynamic conditions to the solute interdiffusion, in the initial instants of solidification.