SANTOS, O. C.; http://lattes.cnpq.br/1956855898077569; SANTOS, Oclávio Coutinho dos.
Résumé:
Aluminum alloys are a great option for those who want low cost compared to other metals used
in industry such as Titanium and Carbon Fiber Reinforced Polymer/Plastics, in addition to good
mechanical properties, the 7XXX series aluminum alloys in turn stand out due to their excellent
characteristics in relation to to other aluminum alloys, such as: its low density linked to good
mechanical resistance, in addition to a relatively high hardness in relation to other aluminum
alloys. However, when subjected to fusion joining techniques, this material does not have good
weldability. One of the possible solutions to this bottleneck is to use solid state welding
techniques, such as the FSW process, however, this process has several variables that influence
the occurrence of welding defects, consequently, on the mechanical properties of these joints.
This work aimed to measure the thermal cycles and correlate it with the mechanical properties
and the occurrence of defects in 7075-T651 aluminum alloy joints welded by the FSW process,
with the aim of evaluating the influence of the peak temperature and rate. of cooling on the
quality of the joint depending on the welding parameters used. For mechanical characterization,
uniaxial tensile tests, 60º root bending, analysis of macro and microstructures, Vickers hardness
test and finally fractography were carried out. For joints with higher feed and rotation speeds
(117 mm/min and 1585 RPM), a higher peak temperature (375,700 °C) and a higher cooling
rate (7,745 °C/s) were found in relation to the others. joints 1 and 3 (47 mm/min and 470 RPM)
which had lower values of peak temperature and cooling rate (358.735 °C and 3.226 °C/s,
respectively), which led to the appearance of defects such as burr, finish coarse surface, lack of
filling in the mixing zone and lower tensile strength. With these temperature analyzes it can be
concluded that for this alloy lower speed parameters imply peak temperatures and lower cooling
rates inducing a higher quality in the joints, higher temperatures induced greater defects in the
joints.