Laser joining of aluminum to steel aiming at eco-efficient applications

Laburpena

The great global concern about issues related to climate change is undeniable, one of the main causes of global warming being the emission of greenhouse gases. In the scenario of the transport industry sector, weight reduction is considered an efficient way to reduce the energy demand of vehicles and, consequently, to reduce greenhouse gas emissions. Therefore, interest arises in the use of structural components made of alloys that have high specific strength. The interest in optimizing the use of these materials in manufacturing processes brings with it the need to join dissimilar materials, guaranteeing their structural integrity. Laser welding stands out among welding processes for providing high energy density and moderate heat input, generating joints with reduced thermally affected areas and low levels of distortion, as well as high processing speeds, resulting in high productivity when compared to processes. conventional welding. The high energy concentration of a laser beam provides sufficient heat to perform welding, while providing control of the growth of intermetallic compounds at the interface of the junction of dissimilar materials. The present doctoral thesis aims to obtain dissimilar laser welds with good metallurgical and mechanical properties, aiming to reduce the weight of metallic structures used in the transport industry. To achieve this objective, the optimization of the experimental conditions was sought The evaluation of the welded joints was carried out through microstructural characterization and mechanical tests. For the materials used, ranges of combined parameter values were defined, obtaining satisfactory joints and avoiding excessive welding imperfections, with a homogeneous intermetallic layer 3 ± 1 µm thick. Tensile tests revealed that the dissimilar joints showed maximum tensile strength values as high as 169 MPa. The hardness and modulus of elasticity of the intermetallic layer evaluated by nanoindentation hardness tests were 11.2 ± 0.7 GPa and 257 ± 24 GPa, respectively. The intermetallic layer was composed of Fe2Al5, Fe4Al13 and Fe4Al17.5Si1.5. These phases were detected using a multi-technique approach, based on electron diffraction-based microscopy techniques