SOUSA, J. W. A.; http://lattes.cnpq.br/1355384774544057; SOUSA, José Wallisson de Abreu.
Resumo:
In the midst of the modern world in which we currently live, the search for materials that
combine a satisfactory resistance/weight ratio has been a stage of worldwide interest in the
industrial sector, especially the transport sector. In this context, magnesium alloys gain
prominence when used in automobile components to improve their efficiency. However, one
of the challenges in applying these materials is obtaining welded joints, as this type of material
has presented limitations when subjected to conventional processes by electric arc fusion. In
this sense, the solid-state friction stir welding process appears as a good alternative for joining
these alloys. Therefore, this work aims to evaluate the influence that welding parameters have
on the microstructure and mechanical properties of welded joints made of AZ31 magnesium
alloy. The joints were produced based on different conditions defined through experimental
planning using a three-axis universal milling machine. Microstructural and mechanical
characterization of the welded joints were carried out, according to optical microscopy and
uniaxial tensile and Vickers microhardness tests, respectively, as well as fractographic analysis
of the fracture surfaces via scanning electron microscope. The results demonstrated a good
visual appearance of the joints, showing the absence of cracks and lack of filling. Different
levels of mechanical resistance were obtained, reaching 197 MPa. The average grain sizes of
the mixing zone were smaller than those of the base material, showing reductions of up to 74%.
Resulting in obtaining higher levels of microhardness in cases of smaller grain size. The
fractographic images showed a considerable presence of dimples, characterizing ductile
fracture of the welded joints. Therefore, the varied temperature levels resulting from the
different welding parameter conditions imposed were decisive for the microstructural behavior,
which consequently influenced the mechanical behavior.
