Correlações entre parâmetros estruturais e microdureza em ligas Al-Si-Cu obtidas através do processo squeeze casting

Abstract

Squeeze Casting is a casting process where the molten metal, when leaked, is solidified under pressure into a metal shell and closed by a punch. The process gives the components manufactured a considerable increase in mechanical properties, such as hardness and tensile strength. It is an economical and simple technique, being used in large scale in the casting of aluminum alloys, magnesium, copper, stainless steels, among others. Aluminum and its alloys are one of the most attractive materials for applications in the industry due to its characteristics and properties. The alloys of the Al-Si-Cu system are widely used because they present some properties that favor the processing and the application of these alloys as high fluidity and good resistance, being very used in the automotive and aeronautical industries, for example. During the alloying solidification process, the most frequently observed morphology is dendritic, which can be characterized by primary (?1), secondary (?2) and tertiary (?3) dendritic spacings. Studies analyze the influence of thermal and microstructural variables of alloys on mechanical properties, showing the importance of dendritic spacings in the final properties. In the present work, the alloys used were Al-5,5% Si-3% Cu, Al-7,5% Si-3% Cu and Al-9% Si-3% Cu solidified under pressures of 0, 50, 100 and 150 MPa. The purpose was to verify how the pressure and solute content influence the macro-structure, microstructure and Vickers microhardness of the Al-Si-Cu system alloys. The obtained results showed in relation to the macrostructure that the variations of the composition of the alloy contributed to the refining of the grains in general. As for ?2, the decrease occurred with the increase of the pressure, as well as with the increase of the solute content. Vickers microhardness, on the other hand, presented increasing values as the pressure increased, except for the pressure of 150 Mpa. The values of Hv also increased when the solute content in the alloys increased.