Browsing by Author "Loureiro, Altino"
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- Nugget Formation and Mechanical Behaviour of Friction Stir Welds of Three Dissimilar Aluminum AlloysPublication . Manuel, Neves; Galvão, Ivan; Leal, Rui M.; Costa, José D.; Loureiro, AltinoThe aim of this research was to investigate the influence of the properties of the base materials and welding speed on the morphology and mechanical behavior of the friction stir welds of three dissimilar aluminum alloys in a T-joint configuration. The base materials were the AA2017-T4, AA5083-H111, and AA6082-T6 alloys in 3 mm-thick sheets. The AA6082-T6 alloy was the stringer, and the other alloys were located either on the advancing or retreating sides of the skin. All the T-joint welds were produced with a constant tool rotation speed but with different welding speeds. The microstructures of the welds were analyzed using optical microscopy, scanning electron microscopy with energy dispersive spectroscopy, and the electron backscatter diffraction technique. The mechanical properties were assessed according to micro-hardness, tensile, and fatigue testing. Good quality welds of the three dissimilar aluminum alloys could be achieved with friction stir welding, but a high ratio between the tool's rotational and traverse speeds was required. The welding speed influenced the weld morphology and fatigue strength. The positioning of the skin materials influenced the nugget morphology and the mechanical behavior of the joints. The joints in which the AA2017 alloy was positioned on the advancing side presented the best tensile properties and fatigue strength.
- Residual stresses profiles of cladded austenitic stainless steel evaluated by X-ray diffraction and by incremental hole-drilling methodPublication . Marques, Maria José; Batista, António Castanhola; Coelho, Luís Manuel de Jesus; Nobre, João P.; Loureiro, AltinoThe samples studied in this paper were carried out using carbon steel plates, cladded on one of the faces with stainless steel filler metals by submerged arc welding (SAW). After cladding, the samples were submitted to post-weld heat treatments under different conditions and then stainless steel coating surfaces were milled and mechanically polished, as in the industrial application. The residual stress analysis was performed by X-ray diffraction (XRD) and incremental hole-drilling methods (IHD). The residual stress profiles showed different values in-depth in each sample, depending on the heat treatment. The hole-drilling method was applied in several points of each stainless steel sample surface and the results presented similar profiles of evolution. However, compressive stresses increase when the heat treatment temperature rises.