Resumo:
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.
