Influência da fase β-Al5FeSi no processo de torneamento cilindrico de uma liga A356-T6 reciclada

Abstract

The use of secondary (recycled) aluminum alloys has been increasing every year due to sustainable and energy issues involved in their production. One of the biggest problems in the use of these alloys is linked to the high iron content present when compared to primary alloys, produced from bauxite. When it comes to Al-Si alloys, the presence of high levels of silicon with iron favors the formation of the b-Al5FeSi phase, known to have negative effects on aluminum, reducing its resistance and ductility, which limits its application and compromises forming processes. This work aimed to evaluate the influence of high iron contents in a recycled alloy during the machining process, with the aid of the DOE technique. For this, a secondary aluminum alloy A356 was remelted with three different contamination conditions (0.2%, 1% and 3% of iron weight) and two solidification conditions in a metallic mold (at room temperature and preheated to 200ºC). All samples underwent solubilization heat treatment at 540ºC for 4 hours with cooling in water and artificial aging at 155ºC for 5 hours and cooling in air. After heat treatment, the test specimens were taken to the SEM to identify the b phase generated and then proceeded to the machining procedure. Cylindrical turning was performed using a completely randomized design with 4 factors: 3 levels of iron contamination, 2 levels of cooling rate, 2 levels of feed rate and 2 levels of cutting speed. As process response variables, cutting and feed forces were obtained, in addition to surface roughness Ra, Rz and R3z. It can be concluded that the addition of iron contents to the A356 alloy provided significant reductions in the cutting forces while the roughness values did not suffer great influences, but, even so, they presented a worse visual aspect after the process.